CN102808429A - Pile foundation soaking load test method based on creep-strain separation - Google Patents

Abstract

The invention discloses a pile foundation soaking load test method based on creep-strain separation, which comprises the steps as follows: firstly, a constant load is loaded; secondly, strain values of a pile body and internal force of the pile body before the soaking are tested, that is, when the settlement of a test pile is stabilized, the strain values in different depth positions of the pile body of the test pile are tested and the internal force in different depth positions of the pile body of the test pile before the soaking are analyzed; thirdly, the soaking is conducted and the strain values of the pile body during the soaking are tested, that is, when the settlement of the test pile is stabilized, the test pile is soaked, and after the test pile is soaked, the strain values in different depth positions of the pile body of the test pile are tested at regular intervals of Delta t; fourthly, an actually measured creep degree function of a calibration section is obtained; fifthly, the creep degree function during each loading age is obtained; and sixthly, the strain values of the pile body and the internal force of the pile body are calculated after creep separation during the soaking. The method disclosed by the invention has the advantages that the steps are simple, the testing is convenient, creep and strain can be separated from a pile body strain test result simply, conveniently, rapidly and accurately, so that the test result approximates to the practical stress state of the pile body as much as possible.

Description

Pile foundation ponding loading test method based on the strain separation of creeping

Technical field

The present invention relates to a kind of pile foundation ponding loading test method, especially relate to a kind of pile foundation ponding loading test method of separating based on the strain of creeping.

Background technology

Early eighties; Swiss Confederation's Zurich University of Science and Technology rock and construction of tunnel are that professor K.Kovari etc. has proposed collimation method monitoring principle (Linewise observation), are different from the some method monitoring principle (Pointwise Observation) of counting representative with strain; And developed a series of portable instrument (comprising the slip micrometer) according to the collimation method monitoring principle; Fixedly bury the formula instrument underground to be different from strain meter, multiple spot extensometer etc., this quasi-instrument has been declared patent and has been entrusted the production and sales of Switzerland Solexperts AG company.

The slip micrometer is that it can 1m be the strain that gauge length is measured line direction continuously according to a kind of portable high-accuracy strain testing instrument of collimation method monitoring principle development, and then calculates the stress and the displacement of each point.This series instrument is by Switzerland's development and production; The later stage eighties 20th century is introduced China; Obtained successful Application in the engineering site monitorings such as pile foundation, deep foundation ditch, tunnel, side slope, dam at home, similar tester with other is compared, and can obtain higher measuring accuracy.The transportable test panel instrument is counted in the slip micrometer; It measures the mean strain of adjacent point-to-point transmission serially; So just can derive the displacement of axial strain distribution and arbitrfary point on the whole piece survey line; One cover instrument can be used for a plurality of borings and a plurality of engineering, is specially adapted to the on-the-spot strain of geotechnical engineering (distortion) monitoring.During actual the test, the slip micrometer can move freely and measure continuously the relative deformation between adjacent 2 points (spacing is 1000mm) along survey line in measured medium, and resolution ratio is strain and the deformation test instrument of 0.001mm/m.

The slip micrometer mainly is made up of test probe, survey pipe (English name is Measuring pipe), data collecting instrument, guide rod (also claiming measuring staff) etc., wherein surveys pipe and is made up of plastic bushing (English name is Casing) and mark (English name is Measuring Mark).Wherein, the mark measurement sign that conical ring that materials such as hard metal or duroplasts process and shell are formed of serving as reasons; Test probe adopts ball awl positioning principle to measure the mark on the pipe, and sensor accuracy is very high, before and after each the measurement, carries out periodic calibration, can arrive very high certainty of measurement and long-time stability.During actual the test, a mark is laid at every meter interval on the plasticity sleeve pipe, and survey line is divided into plurality of sections, and through grouting, mark is cast in measured medium securely, when measured medium deforms, will drive mark deform in same pace with it.Thereby measure each gauge length piecemeal over time with the slip micrometer, thereby obtain reflecting the deformation distribution rule of measured medium along survey line.

Collapsible loess is a kind of special soil; Extensively be distributed in northern China; It can sink under the effect of power and water, and wherein self weight collapse loess will be sunk by the water logging bubble under the effect of last earthing gravity pressure, thereby causes the stake in the self weight collapse loess to produce the negative friction effect.In Collapsible Loess District, concrete pile is main pile foundation type.Be arranged in the pile foundation in collapsible loess place; When settlement by soaking soil layer immersion deflection during greater than the pile foundation deflection; The saturated yielding soil layer produces relatively to pile foundation, and all certain thickness settlement by soaking soil bodys of stake are suspended on the pile body through frictional force, and test pile is produced the negative friction effect.When the collapsible loess field adopts pile foundation to use as the basis of important engineering on the ground; Negative friction performance proterties for research Collapsible Loess District pile foundation; And parameter such as required negative friction size and Depth of Neutral during the design of definite pile foundation engineering; Often carry out the on-the-spot submerging test of collapsible loess place pile foundation, actual measurement pile foundation negative friction force and other correlation technique parameters are carried out Pile Foundations Design.

Before the eighties in 20th century, adopt suspension method to carry out the experimental study of loess place pile foundation negative friction force more.Development along with measuring technology; Be employed in after the nineties in 20th century more and bury sensor in the pile body underground and test the test of carrying out negative friction through internal force; Common way is in loess immersion process; Keeping the test pile stake, to push up constant load (comprise zero load) constant; In pile body, bury the situation that sensor test loess in immersion pile body concrete strain in the sinking process takes place to add underground; Calculate the axle power of the different test of pile body section by elastic theory formula

(1), and then obtain pile side resistance (containing negative friction size and Depth of Neutral).Q in the formula (1) _iFor axle power and its unit of pile body i section part is kN, Be the strain mean of pile body i section part, E _iFor pile shaft material modulus of elasticity and its are kPa for unit, A _iFor pile body section area and its unit are m ²

Yet bury underground in the pile foundation submerging test that sensor carries out in employing, required time (beginning to sedimentation basicly stable from immersion) of collapsible loess immersion settlement stability is longer, and test generally needs to continue January～March.In this process; Test pile pile body concrete under the effect of axle power except that elastic strain takes place; Also can creep; Therefore, under test pile ambient conditions (temperature and humidity) remains unchanged condition, be embedded in the strain that the sensor test in the pile body obtains and in fact comprised elastic strain and crept two parts.In the middle of test data housekeeping in the past; Often ignore the influence of creeping; The strain substitution formula (1) that directly test is obtained is calculated pile body axle power; When a stake top place reference axis power and a stake top application add load when inconsistent, generally less than 1 fixedly correction factor (making in formula (1) both sides, place, stake top equal) the axle power of pile body is revised through increase by one on formula (1) right side.

To sum up, owing to the pile foundation ponding loading test need carry out the long period, under action of long-term load; Elastic strain except that taking place in concrete; Also can creep, but in test job in the past, ignore the influence of creeping; Will survey strain substitution elastic theory design formulas and calculate pile body axle power, pile body axle power result of calculation certainly will have than mistake.In fact, need in the strain testing result, separate the concrete elastic strain and creep, after the value of creeping in the deduction actual measurement strain, calculate by elastic theory again and just can make pile body axial force test result be tending towards reality.

Summary of the invention

Technical problem to be solved by this invention is to above-mentioned deficiency of the prior art; A kind of pile foundation ponding loading test method of separating based on the strain of creeping is provided; Simple and the convenient test of its method step; Can easy from the pile strain test result, fast and accurately separate the strain of creeping, make test result as far as possible near the actual stress state of pile body.

For solving the problems of the technologies described above, the technical scheme that the present invention adopts is: a kind of pile foundation ponding loading test method of separating based on the strain of creeping is characterized in that this method may further comprise the steps:

Step 1, constant load load: the test pile of from top to bottom construction being accomplished loads, and the load that is loaded on the test pile stake top is F _NThe stress that is applied on the said test pile stake top

A is the dowel section area of test pile in the formula;

Said test pile is the concrete pile in being laid in the collapsible loess stratum vertically, and test pile leaves pile crown more than ground;

Pile strain value and the test of pile body internal force before step 2, the immersion: when treating the test pile settlement stability; Adopt said slip micrometer that the strain value at test pile pile body different depth place is tested, and handle pile body axle power and the pile side resistance that draws the preceding test pile pile body different depth place of immersion based on test result analysis;

Before in the step 1 test pile being loaded, in test pile, lay the survey pipe of said slip micrometer earlier, said survey pipe is vertically in the pile body that is laid in test pile; Said survey pipe is by plasticity sleeve pipe and a plurality of mark that is installed in from the bottom to top on the said plasticity sleeve pipe of the equal opening in two ends are formed up and down; Mark with the ground flush in a plurality of said marks is a mark one; Be positioned in a plurality of said marks said mark one top and with said mark one adjacent mark be the top mark, said top mark is positioned at demarcates section, and the distance of said top mark between pushing up with the test pile stake is greater than the external diameter of test pile; The sections of said test pile between said top mark and said mark one is for demarcating section;

Step 3, immersion and pile strain value test between soaking period: when treating the test pile settlement stability, test pile is soaked, this moment test pile pile top load to keep the load time be τ ₀After the immersion, per interval △ t adopts said slip micrometer that the strain value at test pile pile body different depth place is once tested; Wherein, △ t=24 hour ± 5 hours; And after m the test, the actual measurement strain value at the test pile pile body different depth place in m the different test moment between corresponding acquisition soaking period;

Wherein, m different tests are respectively t constantly from front to back between soaking period ₁, t ₂, t ₃... t _m, the time interval between adjacent two tests constantly in front and back is △ t, and pile top load is kept load time τ ₀Be positioned at test t constantly ₁Before and the time interval between the two be △ t;

Between soaking period, the stress that is applied on the said test pile stake top remains unchanged;

Step 4, a demarcation section actual measurement creep degree function obtain, and its acquisition process is following:

Step 401, the strain of demarcating section between the soaking period calculating of creeping: according to the test result in step 2 and the step 3; Strain value with m between soaking period different tests demarcation section constantly; All behind the strain value of the preceding demarcation section of deduction immersion, the strains that obtain m difference test demarcation section constantly under stress

effect are crept;

The strain that step 402, unitstress effect are demarcated section down calculatings of creeping: with stress in the step 401

effect down the strains of m different tests demarcation section constantly creep, convert under the unitstress effect strains that m difference test the demarcation section in the moment into and creep;

Step 403, the match of demarcation section creep degree function: the strains according to m different tests demarcation section constantly under the unitstress effect that is obtained in the step 402 are crept, and the employing polynomial fitting method simulates the creep degree function C (t, the τ that demarcate section between soaking period ₀), and said creep degree function C (t, τ ₀) be that test pile is τ in load age ₀The time the creep degree function;

The creep degree function of step 5, arbitrary load age obtains: according to the creep degree function C (t, the τ that simulate in the step 403 ₀), and adopt aging theory, nativistic theory or aging and congenital binding isotherm, extrapolate said test pile at arbitrary load age τ _iThe time creep degree function C (t, τ _i), i=1,2,3 wherein ... M;

When adopting aging theory to calculate, C (t, τ _i)=C (t, τ ₀)-C (τ _i, τ ₀);

When adopting nativistic theory to calculate, C (t, τ _i)=C (t-τ _i+ τ ₀, τ ₀);

It to be aging when calculating when adopting with congenital binding isotherm,

$C(t,{\mathrm{\τ}}_i)=\frac{C(t,{\mathrm{\τ}}_0)-C({\mathrm{\τ}}_i,{\mathrm{\τ}}_0)+C(t-{\mathrm{\τ}}_i+{\mathrm{\τ}}_0,{\mathrm{\τ}}_0)}{2};$

Step 6, the separation back pile strain value of creeping between soaking period and pile body internal force are calculated: with testing m different actual measurement strain value of testing test pile pile body different depth place constantly between the soaking period that draws in the step 3; After all eliminating creep of concrete, obtain the separation back strain value of creeping at m different tests test pile pile body different depth place constantly between soaking period; Simultaneously, corresponding extrapolate eliminate behind the creep of concrete test pile pile body different depth be between soaking period m different tests axle power constantly with creep separate after pile-side negative friction;

Be in any test t constantly for the arbitrary depth z of test pile pile body _nActual measurement strain value ε _n ^*When (z) eliminating creep of concrete,

According to formula ${\mathrm{\ϵ}}_n\left(z\right)=\frac{P_n\left(z\right)}{\mathrm{EA}}={{\mathrm{\ϵ}}_n}^{*}\left(z\right)-\frac{P_0\left(z\right)}{A}C(t_n,{\mathrm{\τ}}_0)-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{{\mathrm{\Δ\; P}}_i\left(z\right)}{A}C(t_n,{\mathrm{\τ}}_i),$ Calculate the arbitrary depth z of test pile pile body and be in any test t constantly _nCreep and separate the back strain value, wherein n is natural number and n≤m; In the formula, ε _n(z) be in test t constantly for test pile pile body depth z after eliminating creep of concrete _nCreep and separate back strain value, ε _n ^*(z) the test pile pile body depth z that draws for test in the step 3 is in test t constantly _nThe actual measurement strain value, P _n(z) be in test t constantly for test pile pile body depth z after eliminating creep of concrete _nPile body axle power, and ${\mathrm{\Δ\; P}}_n\left(z\right)=\frac{1}{1+\mathrm{EC}(t_n,{\mathrm{\τ}}_n)}\left\{E\right[{{\mathrm{A\ϵ}}_n}^{*}\left(z\right)-P_0\left(z\right)C(t_n,{\mathrm{\τ}}_0)-\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{\mathrm{\Δ\; P}}_i\left(z\right)C(t_n,{\mathrm{\τ}}_i)]-P_0\left(z\right)-\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{\mathrm{\Δ\; P}}_i\},$ P ₀(z) the preceding pile body axle power of test pile pile body depth z place immersion that draws for analyzing and processing in the step 2, A is the dowel section area of test pile, E is the pile concrete modulus of elasticity of test pile, C (t _n, τ ₀) be (t, the τ of creep degree function C described in the step 4 ₀) at test moment t _nThe time functional value, C (t _n, τ _i) be (t, the τ of creep degree function C described in the step 5 _i) at test moment t _nThe time functional value, C (t _n, τ _n) be creep degree function C (t, τ _n) at test moment t _nThe time functional value;

Test pile pile body depth z is in test t constantly after waiting to extrapolate the elimination creep of concrete _nAxle power after, also need according to formula

Test pile pile body depth z is in test t constantly after calculating the elimination creep of concrete _nPile-side negative friction.

Above-mentioned pile foundation ponding loading test method of separating based on the strain of creeping; It is characterized in that: the test pile described in the step 1 is cylindrical stake; And what pile foundation ponding loading test of all side excavation formation of test pile was used tests pits; Said testing pits is flat hole, and flush at the bottom of the hole in said mark one and said flat hole; A said demarcation section arranged outside has a tank, and said tank is that cylindrical tank and its are coaxial laying with test pile;

When in the step 3 test pile being soaked, adopt pumping system to continue water filling in tank, after institute injects underground water and fills with tank, overflow from tank and to flow into the maceration of testing pits also freely to descend and steep the residing collapsible loess of test pile stratum;

Said pumping system comprises draws water pipeline and underground water is delivered to the pumping equipment in the tank through the pipeline that draws water, and the rear end and the pumping equipment of the said pipeline that draws water join, and the front end of the pipeline that draws water extends the bottom land of tank from top to bottom; The height of said tank is not less than the height of said top mark.

Above-mentioned pile foundation ponding loading test method of separating based on the strain of creeping is characterized in that: the quantity of surveying pipe described in the step 2 is one or more;

When the quantity of said survey pipe was many, the structure of many said survey pipes was all identical with size, and many said survey pipes along the circumferential direction evenly are laid in the test pile;

When adopting said slip micrometer that the strain value at test pile pile body different depth place is tested in the step 2; The strain value at the many groups of preceding test pile pile body different depth places of immersion that draw is tested in corresponding acquisition respectively by many said survey pipes; After afterwards the strain value at test pile pile body different depth place before the many groups of immersions being averaged, obtain the mean strain value at the preceding test pile pile body different depth place of immersion; Subsequently, based on the mean strain value at test pile pile body different depth place before the immersion that is obtained, extrapolate the pile body axle power and the pile side resistance at the preceding test pile pile body different depth place of immersion;

After m the test, corresponding acquisition is tested the many groups test data that draws by many said survey pipes respectively in the step 3, and each organizes the actual measurement strain value that said test data includes m different tests test pile pile body different depth place constantly between soaking period;

The strain value of m different tests demarcation section constantly between soaking period in the step 401, correspondence is respectively the mean strain value that many said survey pipes are tested m different tests demarcation section constantly between the soaking period that draws;

ε described in the step 6 _n ^*(z), the test pile pile body depth z that draws for many said survey pipe tests is in test t constantly _nAverage actual measurement strain value.

Above-mentioned pile foundation ponding loading test method of separating based on the strain of creeping; It is characterized in that: the bottom of said tank is provided with a plurality of infiltrations hole; A plurality of said infiltrations hole along the circumferential direction evenly is laid in the outside all around of test pile, and a plurality of said infiltration Kong Jun is vertically to laying.

Above-mentioned pile foundation ponding loading test method of separating based on the strain of creeping is characterized in that: when test pile being loaded in the step 1, adopt device for measuring force to the said load F that is applied on the test pile stake top from top to bottom _NDetect in real time, and with the testing result synchronous driving to data processor;

When adopting said slip micrometer that the strain value at test pile pile body different depth place is tested in the step 2; The data collecting instrument of said slip micrometer with the test result synchronous driving to data processor; Said data processor carries out analyzing and processing to test result, and corresponding pile body axle power and the pile side friction that draws the preceding test pile pile body different depth place of immersion; And the data collecting instrument of the micrometer of slip described in the step 3; The test pile pile body different depth that test is drawn is in m different actual measurement strain value synchronous driving constantly to said data processor of testing between soaking period; Said data processor carries out analyzing and processing according to the described method of step 4 to step 6 again, and handled draw eliminate test pile pile body different depth behind the creep of concrete and be between soaking period m different tests creeping constantly and separate after strain value, pile body axle power and pile-side negative friction.

Above-mentioned pile foundation ponding loading test method of separating based on the strain of creeping; It is characterized in that: the axle power that also needs in the step 6 to be in m the different test moment between soaking period according to test pile pile body different depth behind the elimination creep of concrete of extrapolating is separated the back pile-side negative friction with creeping, and extrapolates the Depth of Neutral of test pile between soaking period.

Above-mentioned pile foundation ponding loading test method of separating based on the strain of creeping; It is characterized in that: the test pile described in the step 1 is a bored pile; And behind the stake hole forming of said bored pile; Earlier said survey pipe is installed in the said stake hole, more said bored pile is carried out the concrete spouting construction.

Above-mentioned pile foundation ponding loading test method of separating based on the strain of creeping is characterized in that: when test pile being loaded in the step 1, adopt charger to load from top to bottom; Said charger comprises two at the anchoring pile of the test pile left and right sides be erected on two loading equipemtns between the said anchoring pile, said loading equipemtn be positioned at test pile directly over.

Above-mentioned pile foundation ponding loading test method of separating based on the strain of creeping, it is characterized in that: the test pile described in the step 1 is a pile for prestressed pipe; After treating that said prestressing pipe pile construction is accomplished, in the said pile for prestressed pipe that construction is accomplished, install again and survey pipe, and said survey pipe is vertically to the pile tube stake core middle part that is laid in said pile for prestressed pipe; Said top mark is the mark that is positioned at topmost in a plurality of said marks;

After treating the installation of said survey pipe; Adopt grouting equipment from the bottom to top to the pile tube stake core of said pile for prestressed pipe and survey in the cavity between the pipe and inject packing material again, the mixed serum of said packing material for being uniformly mixed to form according to the ratio of weight ratio 1000 ︰ 600～1200 ︰ 75 by water, cement and swell soil.

Above-mentioned pile foundation ponding loading test method of separating based on the strain of creeping, it is characterized in that: a plurality of said marks are even laying in the step 1, and the spacing between neighbouring two said marks is 1m; In the step 3 △ t=24 hour.

The present invention compared with prior art has the following advantages:

1, simple, the reasonable in design and realization convenience of method step, input cost is low.

2, according to the linearity elimination of the theoretical derivation pile body axle power computational methods after the influence of creeping of creeping, expression formula is simple, and when internal force monitoring time at interval not quite the time, can calculate the pile body internal force under each monitoring time step by step.

3, through constant pile top load, unsettled demarcation section is set near the stake top, can obtain a creep degree fundamental curve, press the creep degree curve of nativistic theory and the arbitrary load age of aging theoretical derivation in view of the above, can obtain to comprise an interval value of collateral resistance true value.

4, for to make the creep degree curve of acquisition representative, should control the strength grade of pile concrete, its compressive strength should make test result more accurate greater than 2.5 times of neutral point place stress.

5, adopt the temperature and humidity that section concrete is demarcated in comparatively constant principle control to loess pile foundation submerging test underground water temperature capable of using, make the ambient conditions of itself and bottom pile body basic identical.Concrete when adopting underground water as the immersion water source, and around demarcating section, a tank is set, let underground water get into tank from the bottom; Top is overflowed and is got into immersion and test pits; With play demarcate section temperature substantially constant and with the essentially identical purpose of bottom pile body temperature, it is convenient to realize, input cost is low.Simultaneously; Also there be the problem similar with temperature in the humidity of demarcating section; If the infiltration hole is set in tank, can make that the concrete humidity of pile body (one of curing condition) reaches basic identical rapidly up and down, the creep degree function that makes the demarcation section record is more representative.

6, when test pile is pile for prestressed pipe; Survey pipe mounting method step is simple, easy and simple to handle and input cost is low; Survey pipe installation steps are reasonable in design and workable, and the fast and survey pipe installation quality height of survey pipe installation rate efficiently solves and survey the technical barrier that pipe is installed in pile for prestressed pipe simultaneously; Guaranteed to survey pipe and be positioned at the test position of pile for prestressed pipe, accurately recorded the pile lining strain thereby can survey.And when test pile is pile for prestressed pipe; The packing material design of components that is adopted is reasonable and result of use good; Through between pile for prestressed pipe and survey pipe, pouring into a mould packing material; The pile lining strain is passed to through packing material survey pipe, survey the pipe strain energy through test and accurately reflect the strain value of pile lining under the effect of load.

7, method step is reasonable in design and realize conveniently, demarcates section by strain testing is installed in test pile with surveying pipe monitoring pile strain, more than ground, being provided with; When carrying out the internal force test, demarcate section and be soaked in simultaneously among the metastable underground water of temperature with the pile body that buries, the temperature and humidity that the maintenance test pile is demarcated section concrete is constant and consistent with the bottom pile body, and the strength grade of concrete of control test pile; According to demarcating section pile top load value and each strain testing result; Obtain test pile and demarcate the relation of stress, strain and the monitoring time of section; Set up representative creep degree function curve; It specifically is the elastic strain value that load at the same level before the demarcation section strain value deduction immersion of immersion period detecting is measured down; Obtain demarcating between soaking period the strain of creeping of section; Obtain to demarcate section with the concrete creep that the testing time increases, it is converted into creeping under the unitstress effect gets final product; At last according to the creep degree function curve, and under principle of stacking and linearity are crept assumed condition from test pile strain testing result deduction creep after the strain, adopt elastic theory to calculate test pile internal force.Because the strain testing result between soaking period has comprised elastic strain and has crept the strain thereby the separation of need creeping.And when the concrete strength of control test pile during greater than 2.5 times of neutral point place stress; Can make creeping that the pile body concrete takes place creep, adopt linear creeping theoretical the creep of concrete that causes under the long duration load to be eliminated for linearity, when compressive stress hour; The limiting value of having crept under the stress long term; And the value of creeping any time is approximated to direct ratio with stress, and promptly creep degree and stress are irrelevant, and concrete creeping meets principle of stacking; Under the time dependent loading situation, the typical case who sets up according to the stress increment principle of stacking expression formula of creeping.

8, considered the influence of creep of concrete in the long-term test process of pile foundation internal force; Can easy from the pile strain test result, fast and accurately separate the strain of creeping; Make test result as far as possible near actual; Than the real stress state of exact grasp pile body, thereby the precision of test and the reliability of data, its measuring accuracy height and test data good reliability have been improved.Simultaneously, utilize the more constant principle of underground water temperature, the temperature of pile body up and down is unified to the temperature identical with underground water, thus reduced the influence of temperature to pile strain, make the test data good stability, certainty of measurement is higher.

9, because in the pile foundation submerging test; The amount of creeping that pile concrete produces under action of long-term load is bigger; Should take into full account the influence that pile body is crept under the action of long-term load, otherwise can bring considerable influence to the pile side resistance analysis result in the loading procedure behind negative friction and the later stage pile peripheral earth settlement stability, even the deviation of occurrence law property; And adopt the present invention can be simply, convenient and will creep effectively to influence and separate; Test result is more accurate, and practical value is high, and popularizing application prospect is extensive.

In sum, the simple and convenient test of the inventive method step can easy from the pile strain test result, fast and accurately be separated the strain of creeping, and makes test result as far as possible near the actual stress state of pile body.

Through accompanying drawing and embodiment, technical scheme of the present invention is done further detailed description below.

Description of drawings

Fig. 1 is a test method FB(flow block) of the present invention.

Stress state sketch map when Fig. 2 carries out submerging test for adopting the present invention to bored pile.

Fig. 3 is by adopting the creep structural representation of curve of the present invention institute acquisitions demarcation section strain.

Stress state sketch map when Fig. 4 carries out submerging test for adopting the present invention to pile for prestressed pipe.

Description of reference numerals:

1-test pile; 2-test pits; 3-demarcation section;

4-tank; 5-survey and manage; 6-motor-pumped well;

7-pumping equipment; 8-anchoring pile; 9-loading equipemtn;

10-pipeline draws water; 11-hole enlargement pile crown; 12-packing material.

The specific embodiment

Embodiment 1

Like Fig. 1, shown in Figure 2, pile foundation ponding loading test method of separating based on the strain of creeping of the present invention may further comprise the steps:

Step 1, constant load load: the test pile of from top to bottom construction being accomplished 1 loads, and the load that is loaded on 1 top of test pile is F _NThe stress that is applied on 1 top of said test pile

A is the dowel section area of test pile 1 in the formula.

Said test pile 1 is the concrete pile in being laid in the collapsible loess stratum vertically, and test pile 1 leaves pile crown more than ground.

In the present embodiment, said test pile 1 is cylindrical stake, and all side excavations of test pile 1 form that a pile foundation ponding loading test uses test pits 2, said testing pits 2 is flat hole, and flush at the bottom of the hole in said mark one and said flat hole.Said demarcation section 3 arranged outside have a tank 4, and said tank 4 is coaxial laying for cylindrical tank and its with test pile 1.The height of said tank 4 is not less than the height of said top mark.

In the present embodiment, a plurality of said marks are even laying, and the spacing between neighbouring two said marks is 1m.

The actual laying when installing also can need based on concrete test, and the spacing between neighbouring two said marks is adjusted accordingly in the scope of 0.999m～1.001m.In the present embodiment, the stake footpath of said test pile 1 be 0.846m, and stake long be 60m, the height of said pile crown is h=d3+d4+ △, wherein d3 is the spacing between neighbouring two said marks, d4 be said test pile 1 directly, △=10cm ± 2cm.The height that the top of said survey pipe 5 exceeds 1 top of test pile is 8cm～20cm.

In the present embodiment, the test pile 1 described in the step 1 is a bored pile, and behind the stake hole forming of said bored pile, earlier said survey pipe 5 is installed in the said stake hole, more said bored pile is carried out the concrete spouting construction.

During practice of construction, said test pile 1 also can be the concrete pile of other type.

In the present embodiment; Said bored pile top is provided with hole enlargement pile crown 11; Said top mark is the mark that is laid in hole enlargement pile crown 11 bottoms; Said hole enlargement pile crown 11 tops are provided with a mark, and the set mark in said hole enlargement pile crown 11 tops is positioned at mark top, said top and it is and the adjacent mark of said top mark that the set mark in said hole enlargement pile crown 11 tops is the mark that is positioned at topmost in a plurality of said marks.

In the present embodiment, adopt the anchoring pile method that pile for prestressed pipe 4 is loaded.During actual tests, also can adopt accumulation load method to load.

In the present embodiment, when test pile 1 being loaded, adopt charger to load from top to bottom.Said charger comprises two at the anchoring pile 8 of test pile 1 left and right sides be erected on two loading equipemtns 9 between the said anchoring pile 8, said loading equipemtn 9 be positioned at test pile 1 directly over.

Said loading equipemtn 9 also comprise be erected on two between the said anchoring pile 8 reaction beam, be laid in the transfer beam directly over the test pile 1 and be positioned at test pile 1 directly over and be laid in the loading equipemtn on the said transfer beam, said reaction beam fills up above said loading equipemtn and between the two the pressurization beam is housed.Said transfer beam middle part has and supplies to survey the survey pipe preformed hole that pipe 5 passes.In the present embodiment, said pressurization beam and said reaction beam all be positioned at test pile 1 directly over, two said anchoring pile 8 symmetries are laid in the left and right sides of test pile 1.

During actual the use, said loading equipemtn comprises a plurality of jack of along the circumferential direction laying, and a plurality of said jack are even laying.In the present embodiment, the quantity of said jack is two.

During actual the loading, take the mode of stage loading that test pile 1 is loaded on trial load, i.e. F _N

Pile strain value and the test of pile body internal force before step 2, the immersion: when treating test pile 1 settlement stability; Adopt said slip micrometer that the strain value at test pile 1 pile body different depth place is tested, and handle pile body axle power and the pile side resistance that draws the preceding test pile 1 pile body different depth place of immersion according to test result analysis.

Before in the step 1 test pile 1 being loaded, test pile 1 in, lay the survey pipe 5 of said slip micrometer earlier, it is vertical in the pile body that is laid in test pile 1 that said survey pipe 5 is; Said survey pipe 5 is by plasticity sleeve pipe and a plurality of mark that is installed in from the bottom to top on the said plasticity sleeve pipe of the equal opening in two ends are formed up and down.Mark with the ground flush in a plurality of said marks is a mark one.Be positioned in a plurality of said marks said mark one top and with said mark one adjacent mark be the top mark, said top mark is positioned at demarcates section 3, and the distance between said top mark and 1 top of test pile is greater than the external diameter of test pile 1.The sections of said test pile 1 between said top mark and said mark one is for demarcating section 3.

In the present embodiment, when in the step 3 test pile 1 being soaked, adopt pumping system to continue water filling to tank 4 in, after institute injects underground water and fills with tank 4, overflow inflow from tank 4 and test pits and 2 also freely descend maceration to steep test pile 1 residing collapsible loess stratum.

Said pumping system comprises draws water pipeline 10 and underground water is delivered to the pumping equipment 7 in the tank 4 through the pipeline 10 that draws water, and the rear end and the pumping equipment 7 of the said pipeline 10 that draws water join, and the front end of the pipeline 10 that draws water extends the bottom land of tank 4 from top to bottom.

In the present embodiment, said pumping equipment 7 groundwater abstraction in motor-pumped well 6.

The bottom of said tank 4 is provided with a plurality of infiltrations hole, and a plurality of said infiltrations hole along the circumferential direction evenly is laid in the outside all around of test pile 1, and a plurality of said infiltration Kong Jun is vertically to laying.In the present embodiment, the quantity in said infiltration hole is two.

In the present embodiment, the internal diameter Φ 2=c * Φ 1 of said tank 4, wherein Φ 1 is the diameter of test pile 1, and c=1.2～2.

During practice of construction, can be according to concrete needs, the internal diameter Φ 2 of tank 4 is adjusted accordingly.

To sum up, said test pile 1 leaves more than 2 the ground of testing pits demarcates section 3,3 one weeks is provided with tank 4 around demarcating section, vertically is provided with in the test pile 1 and surveys pipe 5.Said 2 outer motor-pumped well 6 and the pumping equipments 7 that are provided with groundwater abstraction of testing pits, testing pits is provided with anchoring pile 8 and loading equipemtn 9 in 2.

In the present embodiment; When adopting said slip micrometer that the strain value at test pile 1 pile body different depth place is tested; The strain value at the test pile 1 pile body different depth place that said slip micrometer test draws; Compare the strain value that said test pile 1 pile body different depth place takes place for said charger loading back and before loading.That is to say, before loading in the step 1, adopt said slip micrometer to test earlier, this moment, the measured value at the test pile 1 pile body different depth place that test draws just was the initial displacement value; After loading and after treating test pile 1 settlement stability; Adopt said slip micrometer to test again; This moment, the measured value at the test pile 1 pile body different depth place that test draws just was shift value after loading, and the difference of shift value and initial displacement value just is loaded load F after the loading at said test pile 1 pile body different depth place _NThe time test pile 1 pile body different depth place strain value, and this stress value for immersion before the strain value at test pile 1 pile body different depth place.Subsequently, the strain value at test pile 1 pile body different depth place before the immersion that draws according to test, analyzing and processing draws the pile body axle power and the pile side resistance at test pile 1 pile body different depth place before the immersion.

The process of pile body axle power and pile side resistance that the strain value at test pile 1 pile body different depth place before the immersion that draws according to test, analyzing and processing draw test pile 1 pile body different depth place before the immersion is following:

At first, the strain value at test pile 1 pile body different depth place is drawn out loaded load F before the immersion that test draws according to said slip micrometer _NThe time pile body actual measurement strain curve.

When the quantity of said survey pipe 5 was one, said pile body actual measurement strain curve was that said slip micrometer is tested the curve of the preceding test pile 1 pile strain value of the immersion that draws with change in depth;

When the quantity of said survey pipe 5 is many; The corresponding strain value that draws the preceding test pile 1 pile body different depth place of many group immersions of said slip micrometer; The strain value at said test pile 1 pile body different depth place is managed 5 corresponding with a plurality of surveys respectively before many group immersions; And said pile body actual measurement strain curve is the curve of the mean strain value of test pile 1 before the immersion with change in depth, and said mean strain value is the average of the strain value at said test pile 1 pile body different depth place before many groups are soaked.

In the actual test process; When the quantity of said survey pipe 5 is many; The quantity of used slip micrometer is a plurality of; Correspondingly carry out synchronism detection through a plurality of test probes that are used with many said survey pipes 5 respectively, and a plurality of said test probe is worn supplementary biography with measured data and is delivered to data collecting instrument.That is to say that a plurality of said test probes are tested synchronously.

Secondly, adopt the polynomial fitting method of pile strain curve, above-mentioned pile body actual measurement strain curve is carried out match, obtain loaded load F _NThe time test pile 1 the pile strain matched curve; The pile body match strain value that said pile strain matched curve is a test pile 1 is with the curve of change in depth.

Afterwards, calculate the pile concrete modulus of elasticity of test pile 1 according to formula .

A is that dowel section area and its unit of test pile 1 are m in the formula ², Q _iBe the load F that is loaded on 1 top of test pile _NAnd its unit is kN; ε _0iBe stake top loaded load F _NThe match strain value on 1 top of Shi Suoshu test pile, it can draw according to the pile strain matched curve that match draws.

Then, according to formula P ₀(z)=AE _iε _i(z), calculate the preceding pile body axle power of the arbitrary depth z of test pile 1 pile body place immersion.

A is that dowel section area and its unit of test pile 1 are m in the formula ², ε _i(z) draw the match strain value at the arbitrary depth z of test pile 1 pile body place, P for the pile strain matched curve that draws according to match ₀(z) be the preceding pile body axle power of test pile 1 pile body depth z place immersion, E is the pile concrete modulus of elasticity of test pile 1.

Subsequently, calculate the preceding pile side friction of the arbitrary depth z of test pile 1 pile body place immersion according to formula

.

D is that external diameter and its unit of test pile 1 are m in the formula, P ₀(z) be the preceding pile body axle power of test pile 1 pile body depth z place immersion.

At last, according to formula

Calculate the end resistance of test pile 1; A in the formula ₀For stake end cross-sectional area and its unit of test pile 1 is m ², Q _nthe axle power and the kN of its unit that hold for test pile 1.

Step 3, immersion and pile strain value test between soaking period: when treating test pile 1 settlement stability, test pile 1 is soaked, this moment test pile 1 pile top load to keep the load time be τ ₀(that is to say that this moment, the load age of test pile 1 was τ ₀); After the immersion, per interval △ t adopts said slip micrometer that the strain value at test pile 1 pile body different depth place is once tested; Wherein, △ t=24 hour ± 5 hours; And after m the test, the actual measurement strain value at the test pile 1 pile body different depth place in m the different test moment between corresponding acquisition soaking period.

Wherein, m different tests are respectively t constantly from front to back between soaking period ₁, t ₂, t ₃... t _m, the time interval between adjacent two tests constantly in front and back is △ t, and pile top load is kept load time τ ₀Be positioned at test t constantly ₁Before and the time interval between the two be △ t.

Between soaking period, the stress that is applied on 1 top of said test pile remains unchanged.

In the present embodiment, △ t=24 hour, promptly one day.In the actual test process, can according to actual needs △ t be adjusted accordingly.In the step 1, F _N=3000kN, classification is forced into 3000kN before the immersion; Behind following top settlement stability of this load action, to the immersion in 2 of testing pits, it is constant to keep stake top 3000kN load in the pile peripheral earth generation self-collapsibility infall process; After the day starting at 71 days (stopping after soak 53 days soaking in 2 to testing pits) from immersion, pile peripheral earth is out of shape stable.

Step 4, a demarcation section actual measurement creep degree function obtain, and its acquisition process is following:

Step 401, the strain of demarcating section between the soaking period calculating of creeping: according to the test result in step 2 and the step 3; Strain value with m between soaking period different tests demarcation section 3 constantly; All behind the strain value of the preceding demarcation section 3 of deduction immersion, the strains that obtain m difference test demarcation section 3 constantly under stress

effect are crept.

Wherein, demarcate the strain value of section 3, be specially the strain value between said top mark and the said mark one.

The strain that step 402, unitstress effect are demarcated section down calculatings of creeping: with stress in the step 401

effect down the strains of m different tests demarcation section 3 constantly creep, convert under the unitstress effect strains that m difference test the demarcation section 3 in the moment into and creep.

During actual the conversion; Only need the strain of m different tests demarcation section 3 constantly under stress in the step 401

effect is crept; All divided by after

, the strain that just obtains m different tests demarcation section 3 constantly under the unitstress effect is crept.

In the present embodiment; The strain of m different tests demarcation section 3 constantly under the unitstress effect is crept; Be plotted in the described point mode that to keep the load time with stake top load be abscissa and to creep with the strain of demarcating section 3 be in the plane right-angle coordinate of ordinate, carry out the function match afterwards again.

Step 403, the match of demarcation section creep degree function: the strains according to m different tests demarcation section 3 constantly under the unitstress effect that is obtained in the step 402 are crept, and the employing polynomial fitting method simulates the creep degree function C (t, the τ that demarcate section 3 between soaking period ₀), and said creep degree function C (t, τ ₀) be that test pile 1 is τ in load age ₀The time the creep degree function.

Said creep degree function C (t, τ ₀) for load age be τ ₀The time unitstress effect strain of demarcating section 3 down creep, keep the curve that the load time changes with stake top load, promptly demarcate the section strain curve of creeping, see Fig. 3 for details.

To sum up, what the present invention adopted is the method that the field measurement mode is obtained the creep degree function, and practical operation is very easy, and realizes conveniently, but must carry out having in the load stake (being test pile 1), and its method is near the stake top of test pile 1, to be provided with to demarcate section 3.And, said demarcation section 3 should be apart from the stake top certain distance (in the present embodiment, this distance be d4+ △, wherein d4 be said test pile 1 directly, △=10cm ± 2cm) is to avoid the uneven pile cutoff of test pile 1 cross section upper stress.In the submerging test process, keep pile top load F at negative friction test period (i.e. immersion back) _N(stress that is applied on 1 top of test pile corresponds to

) constant, monitoring is demarcated section 3 and is kept the creep of concrete that the load time increases with stake top load, and it is converted into creeping under the unitstress effect, and adopts curve-fitting method that the monitored data of creeping is carried out match, promptly obtains creep degree function expression C (t, τ ₀).

The creep degree function of step 5, arbitrary load age obtains: according to the creep degree function C (t, the τ that simulate in the step 403 ₀), and adopt aging theory, nativistic theory or aging and congenital binding isotherm, extrapolate said test pile 1 at arbitrary load age τ _iThe time creep degree function C (t, τ _i), i=1,2,3 wherein ... M;

When adopting aging theory to calculate, C (t, τ _i)=C (t, τ ₀)-C (τ _i, τ ₀);

When adopting nativistic theory (being called again continues imitate theoretical) when calculating, C (t, τ _i)=C (t-τ _i+ τ ₀, τ ₀);

It to be aging when calculating when adopting with congenital binding isotherm,

$C(t,{\mathrm{\τ}}_i)=\frac{C(t,{\mathrm{\τ}}_0)-C({\mathrm{\τ}}_i,{\mathrm{\τ}}_0)+C(t-{\mathrm{\τ}}_i+{\mathrm{\τ}}_0,{\mathrm{\τ}}_0)}{2}.$

According to above-mentioned aging theory, nativistic theory or aging and congenital binding isotherm, like known load age τ ₀Creep of concrete degree fundamental curve C (t, τ ₀), through the vertical translation and the horizontal translation of coordinate system, just can obtain arbitrary load age τ respectively _iThe time creep degree function C (t, τ _i).

Wherein, aging theory has been considered the influence of concrete aging to creep deformation; And nativistic theory has been stressed the heredity of creep deformation.In fact, concrete is fairly obvious in the premature ageing characteristic, and the later stage then mainly shows as heredity.For pile foundation submerging test characteristics; Pile concrete length of time is mostly between 28 days to 90 days during immersion; According to relevant creep test result; Creep of concrete truly has with the increase of load age and reduces during the pile foundation submerging test, adopts nativistic theory can over-evaluate the value of creeping, but adopts aging theory also can underestimate the value of creeping.With regard to the negative friction analysis result, the negative friction that obtains of utilization nativistic theory is less than normal, and that aging theory obtains is bigger than normal, and true negative friction value is between the two.Therefore, consider the error that allows on the engineering, the negative friction value that can nativistic theory and aging theory analysis be obtained is in addition on average as the negative friction test value, promptly aging and congenital binding isotherm.

Step 6, the separation back pile strain value of creeping between soaking period and pile body internal force are calculated: with testing m different actual measurement strain value of testing test pile 1 pile body different depth place constantly between the soaking period that draws in the step 3; After all eliminating creep of concrete, obtain the separation back strain value of creeping at m different tests test pile 1 pile body different depth place constantly between soaking period; Simultaneously, corresponding extrapolate eliminate behind the creep of concrete test pile 1 pile body different depth be between soaking period m different tests axle power constantly with creep separate after pile-side negative friction.

Be in any test t constantly for the arbitrary depth z of test pile 1 pile body _nActual measurement strain value ε _n ^*When (z) eliminating creep of concrete,

According to formula ${\mathrm{\ϵ}}_n\left(z\right)=\frac{P_n\left(z\right)}{\mathrm{EA}}={{\mathrm{\ϵ}}_n}^{*}\left(z\right)-\frac{P_0\left(z\right)}{A}C(t_n,{\mathrm{\τ}}_0)-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{{\mathrm{\Δ\; P}}_i\left(z\right)}{A}C(t_n,{\mathrm{\τ}}_i),$ Calculate the arbitrary depth z of test pile 1 pile body and be in any test t constantly _nCreep and separate the back strain value, wherein n is natural number and n≤m; In the formula, ε _n(z) be in test t constantly for test pile 1 pile body depth z after eliminating creep of concrete _nCreep and separate back strain value, ε _n ^*(z) the test pile 1 pile body depth z that draws for test in the step 3 is in test t constantly _nThe actual measurement strain value, P _n(z) be in test t constantly for test pile 1 pile body depth z after eliminating creep of concrete _nPile body axle power, and $P_n\left(z\right)=P_0\left(z\right)+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\Δ\; P}}_i\left(z\right);$ ${\mathrm{\Δ\; P}}_n\left(z\right)=\frac{1}{1+\mathrm{EC}(t_n,{\mathrm{\τ}}_n)}\left\{E\right[{{\mathrm{A\ϵ}}_n}^{*}\left(z\right)-P_0\left(z\right)C(t_n,{\mathrm{\τ}}_0)-\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{\mathrm{\Δ\; P}}_i\left(z\right)C(t_n,{\mathrm{\τ}}_i)]-P_0\left(z\right)-\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{\mathrm{\Δ\; P}}_i\},$

P ₀(z) the preceding pile body axle power of test pile 1 pile body depth z place immersion that draws for analyzing and processing in the step 2, A is the dowel section area of test pile 1, E is the pile concrete modulus of elasticity of test pile 1, C (t _n, τ ₀) be (t, the τ of creep degree function C described in the step 4 ₀) at test moment t _nThe time functional value, C (t _n, τ _i) be (t, the τ of creep degree function C described in the step 5 _i) at test moment t _nThe time functional value, C (t _n, τ _n) be creep degree function C (t, τ _n) at test moment t _nThe time functional value.

Test pile 1 pile body depth z is in test t constantly after waiting to extrapolate the elimination creep of concrete _nAxle power after, also need according to formula Test pile 1 pile body depth z is in test t constantly after calculating the elimination creep of concrete _nPile-side negative friction.

The function C of creep degree described in the step 5 (t, τ _i) in, the creep degree function when i=n is C (t _n, τ _n).

Simultaneously, the axle power that also needs in the step 6 to be in m the different test moment between soaking period based on test pile 1 pile body different depth behind the elimination concrete creep of extrapolating is separated the back pile-side negative friction with creeping, and extrapolates the Depth of Neutral of test pile 1 between soaking period.Concrete reckoning process see for details " Code for design of building " (GB50007-2003), " technical code for building pile foundation " (JGJ94-2008) with " Code for building construction in collapsible loess zone " (GB50025-2004) in pertinent regulations.

In the present embodiment, when test pile 1 being loaded in the step 1, adopt device for measuring force from top to bottom to the said load F that is applied on 1 top of test pile _NDetect in real time, and with the testing result synchronous driving to data processor.And in the loading procedure, adopt the displacement detecting unit that the stake top settling amount of test pile 1 is detected in real time, and with the testing result synchronous driving to data processor.

The actual laying when installing, said displacement detecting unit are the displacement transducer that is laid on the pile crown of test pile 1.Said device for measuring force is the pressure sensor that is laid on the said loading equipemtn.Said device for measuring force and said displacement detecting unit all join with said data processor.Said pressure sensor is between said loading equipemtn and pressurization beam, and pressure sensor and said data processor join.

When adopting said slip micrometer that the strain value at test pile 1 pile body different depth place is tested in the step 2; The data collecting instrument of said slip micrometer with the test result synchronous driving to data processor; Said data processor carries out analyzing and processing to test result, and corresponding pile body axle power and the pile side friction that draws the preceding test pile 1 pile body different depth place of immersion; And the data collecting instrument of the micrometer of slip described in the step 4; The test pile 1 pile body different depth that test is drawn is in m different actual measurement strain value synchronous driving constantly to said data processor of testing between soaking period; Said data processor carries out analyzing and processing according to the described method of step 5 to step 7 again, and handled draw eliminate test pile 1 pile body different depth behind the creep of concrete and be between soaking period m different tests creeping constantly and separate after strain value, pile body axle power and pile-side negative friction.

During practice of construction, the quantity of surveying pipe 5 described in the step 2 is one or more.

When the quantity of said survey pipe 5 was many, the structure of many said survey pipes 5 was all identical with size, and many said survey pipes 5 along the circumferential direction evenly are laid in the test pile 1;

When adopting said slip micrometer that the strain value at test pile 1 pile body different depth place is tested in the step 2; The strain value at test pile 1 pile body different depth places before the many groups of immersions that corresponding acquisition is drawn by 5 tests of many said survey pipes respectively; After afterwards the strain value at test pile 1 pile body different depth place before the many groups of immersions being averaged, obtain the mean strain value at the preceding test pile 1 pile body different depth place of immersion; Subsequently, based on the mean strain value at the 1 pile body different depth place of test pile before the immersion that is obtained, extrapolate the pile body axle power and the pile side resistance at the preceding test pile 1 pile body different depth place of immersion;

After m the test, corresponding acquisition is tested the many groups test data that draws by many said survey pipes 5 respectively, and each organizes the actual measurement strain value that said test data includes m different tests test pile 1 pile body different depth place constantly between soaking period in the step 3;

The strain value of m different tests demarcation section 3 constantly between soaking period in the step 401, correspondence is respectively the mean strain value that many said survey pipes 5 are tested m different tests demarcation section 3 constantly between the soaking period that draws;

ε described in the step 6 _n ^*(z), the test pile 1 pile body depth z that draws for many said survey pipe 5 tests is in test t constantly _nAverage actual measurement strain value.

In the present embodiment, the quantity of surveying pipe 5 described in the step 2 is two.During practice of construction, can test needs, the quantity of surveying pipe 5 is adjusted accordingly according to reality.

To sum up, because creep of concrete is meant concrete when remaining unchanged (be stress) under the long term of a certain constant load, its strain in time and the phenomenon that increases.

Creeping increases and can extend over scores of years, but most ofly in 1-2, occurs, and preceding 2-6 month is with fastest developing speed, is 28 days concrete to load age, during convergence (pile top load keep the load time=ratio of ∞) creeping with elastic strain reaches 2～4.Strictly speaking; Should adopt the nonlinear criterion of creeping to predict the CREEPING IN CONCRETE STRUCTURES distortion; But at present non-linear creeping theoretically also do not reach practical stage, thereby usually thinks approx and exist linear relationship between creep deformation and its stress, obedience Boltzman principle of stacking.Under following condition, measured result and principle of stacking (perhaps linear relationship) are very approaching:

1) numerical value of stress is lower than 40%～50% of concrete strength, or says within the working stress scope;

2) strain value does not reduce during the course;

3) process of creeping does not experience significant dry;

4) stress value does not increase considerably after original upload.

Compare with any one of first three condition, it is less to run counter to the error that last condition causes, last condition can be ignored when calculating usually.In the pile foundation submerging test, condition 1) and 3) can realize through human intervention; Condition 2) satisfied basically, i.e. owing to the development gradually of negative friction, pile strain increases gradually in the pile foundation submerging test.Under principle of stacking and linearity were crept assumed condition, creeping can be expressed as: (2); Formula (2) is discrete, have:

(3); ε in the formula (3) _c(τ) be the t strain of creeping constantly, σ (τ ₀) be τ ₀The stress that constantly applies, Δ σ _iBe τ _iThe stress that constantly applies, C (t, τ ₀) for load age be τ ₀The time the creep degree function, C (t, τ _i) for load age be τ _iThe time the creep degree function.

In conjunction with the definition of creep of concrete, the essence of formula (3) is that the continually varying load is separated into the amount of creeping that time dependent loading is calculated in some constant load stacks.Use it to calculate creeping of pile concrete, need to know discrete load (Δ σ _i) application time τ _iBecause the load time τ of afterbody load before the immersion ₀For known, then can calculate different testing time t in the pile foundation submerging test _n(n=1,2,3 ...) pile body axle power.

Get arbitrary strain testing section (being the arbitrary depth z of test pile 1 pile body place) and be research object, under the pile top load effect, the axle power behind test pile 1 settlement stability is P before the immersion ₀(z) (load time is shorter, can not consider to creep, and directly calculates pile body axle power by formula (3)), the immersion back is along with the development of negative friction, and arbitrary test is t constantly _nAxle power be:

(4); △ P in the formula (4) _i(z) be continually varying, but when internal force monitoring interval (being △ t) is little, can continually varying axle power be dispersed, suppose △ P _i(z) at this testing time t _iWith testing time last time t _I-1(when i=1, t _I-1Be τ ₀) in the middle of τ constantly _iConcentrate and take place.

Then, have according to elastic theory: $\mathrm{EA}({{\mathrm{\ϵ}}_n}^{*}\left(z\right)-{\mathrm{\ϵ}}_c\left(t\right))=P_0\left(z\right)+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\Δ\; P}}_i\left(z\right)$ (5); E is the pile concrete modulus of elasticity of test pile 1 in the formula (5), and A is the dowel section area (being the cross-sectional area of test pile 1 pile body) of test pile 1, ε _n ^*(z) be test moment t _nThe actual measurement strain value that test draws, ε _c(t) be test moment t _nThe strain of creeping (be ε _n(z)), n is test moment t between soaking period _nThe internal force testing time of having monitored.

With formula (3) substitution formula (5), can get after the arrangement:

${\mathrm{\ΔP}}_n\left(z\right)=\frac{1}{1+\mathrm{EC}(t_n,{\mathrm{\τ}}_n)}\left\{E\right[{{\mathrm{A\ϵ}}_n}^{*}\left(z\right)-P_0\left(z\right)C(t_n,{\mathrm{\τ}}_0)-\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{\mathrm{\ΔP}}_i\left(z\right)C(t_n,{\mathrm{\τ}}_i)]-P_0\left(z\right)-\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{\mathrm{\ΔP}}_i\}---\left(6\right);$

According to formula (4) but and recursion calculate n between soaking period (n=1,2,3 ...) inferior (i.e. test is t constantly _n) the axle power in internal force when test, can be used as the fundamental formular of pile foundation submerging test internal force test result analysis.

Elastic strain behind the elimination creep of concrete is:

${\mathrm{\ϵ}}_n\left(z\right)=\frac{P_n\left(z\right)}{\mathrm{EA}}={{\mathrm{\ϵ}}_n}^{*}\left(z\right)-\frac{P_0\left(z\right)}{A}C(t_n,{\mathrm{\τ}}_0)-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{{\mathrm{\ΔP}}_i\left(z\right)}{A}C(t_n,{\mathrm{\τ}}_i)---\left(7\right).$

To sum up, because it is a lot of to influence the factor of creep of concrete, mainly comprise (wherein be in the concrete of air-tight state, scantling does not influence creep) such as concrete composition, ambient conditions (comprise and making and curing condition), stress situation, scantlings.For guarantee test preferably the section of the being demarcated curve of creeping (be creep degree function C (t, τ ₀)) and representative, test pile 1 should satisfy following requirement with monitoring time interval (being Δ t):

The first, concrete strength of pile:

Formula (6) is according to the linearity theoretical axle power design formulas that derives of creeping; Have only the greatest axis power of working as to be suitable for less than 0.4～0.5 times of concrete strength; It is non-linear with appearing to creep above this value, and the creep degree curve makes the problem of creeping complicated more with relevant with stress intensity.Therefore; Should and estimate the downdrag size according to the big or small of the negative friction test period stake top load that loads; Select the proper strength grade (being the strength grade of concrete of test pile 1 pile body) of test pile 1, the compressive strength that makes pile concrete is greater than 2.5 times of neutral point place stress; Otherwise, also can and estimate the downdrag size, the size of the control stake top load that loads according to the concrete strength of pile grade.

The second, submerging test operating mode:

Because when need adopting field trial test creep degree function, thereby must carry out having in the load stake, therefore should not have the test of the negative friction of load stake separately.When need will have the creep degree curve that records in the load stake to apply in the no load stake, two concrete composition, pile time and ambient conditions etc. should be basic identical.

Three, internal force monitoring time interval (being Δ t):

Because the present invention disperses continually varying axle power; And the time of origin of supposition axle power increment is the middle moment at twice internal force monitoring time; Therefore the time interval of internal force monitoring is unsuitable oversize; Especially creeping at the immersion initial stage increases rapidly, and the immersion initial stage with cut off the water during initial stage negative friction (pile body axle power) increases rapidly, generally got 24 hours.

Four, temperature and humidity control:

Since Collapsible Loess District below ground the soil temperature more than the 5m receive the influence of atmospheric temperature comparatively serious, and the temperature below the 5m is comparatively constant below ground.

And that the pile foundation submerging test lasts is longer; Cross over Various Seasonal toward contact; The atmospheric temperature amplitude of variation is bigger; Do not take measures making near the under-represented of the strain of creeping of demarcating section 3 the stake top, even (1 ℃ of the every rising of concrete temperature will produce about 12.4 * 10 the comparatively chaotic situation of actual measurement strain to occur ^-6MPa ^-1The strain of creeping).Therefore; Should take measures to make that the temperature of demarcating section 3 is comparatively constant, and basic identical with the bottom pile body (promptly being arranged in the pile body of soil) of below ground, when adopting underground water as the immersion water source; Can around demarcating section 3, a tank 4 be set; Let underground water get into tank 4 from the bottom, top is overflowed and is got into immersion and test pits 2, with play demarcate section 3 temperature substantially constants and with the essentially identical purpose of bottom pile body temperature.Simultaneously, also there be the problem similar with temperature in the humidity of demarcation section, if the infiltration hole is set in tank 4, can make that the concrete humidity of pile body (one of curing condition) reaches basic identical rapidly up and down, and the creep degree function that demarcation section 3 records is more representative.

Embodiment 2

As shown in Figure 4, in the present embodiment, different with embodiment 1 is: the test pile 1 described in the step 1 is pile for prestressed pipe; After treating that said prestressing pipe pile construction is accomplished, in the said pile for prestressed pipe that construction is accomplished, install again and survey pipe 5, and said survey pipe 5 is vertically to the pile tube stake core middle part that is laid in said pile for prestressed pipe; Said top mark is the mark that is positioned at topmost in a plurality of said marks.And the quantity of said survey pipe 5 is one.The pile body cross section of said pile for prestressed pipe is an annular, and owing to a stake underseal closes, thereby said pile for prestressed pipe end cross section is circular.

After treating that 5 installations are managed in said survey; Adopt grouting equipment from the bottom to top to the pile tube stake core of said pile for prestressed pipe and survey and inject packing material 12 in the cavity between the pipe 5 again, the mixed serum of said packing material 12 for being uniformly mixed to form according to the ratio of weight ratio 1000 ︰ 600～1200 ︰ 75 by water, cement and swell soil.

Thereby in the present embodiment, the mounting method of surveying pipe 5 is different with embodiment 1.When reality was installed surveying pipe 5, its installation process was following:

Water filling in step 101, the pile for prestressed pipe: after said prestressing pipe pile construction is accomplished, to the pile tube stake in-core fills with water of pile for prestressed pipe.

Said pile for prestressed pipe bottom seals is welded with the piling bar point, and said pile tube stake core bottom forms the water storage cavity that top has through piling bar point sealing back.

In the practice of construction process, when pile for prestressed pipe is constructed, construct according to the job practices of conventional prestressed concrete pile.In the present embodiment, said pile for prestressed pipe is assemblied to form by a plurality of joints from the bottom to top, and the joint location between neighbouring two said stake joints adopts welding manner to be connected and sealed.When pile for prestressed pipe is constructed,, accomplish stake, pitching pile, pile sinking, pile extension and the pile follower process of hanging successively according to conventional method.Actual when carrying out pile extension, adopt welding equipment around one week of pile for prestressed pipe joint location, and save neighbouring two said stakes integrally welded.And when pile for prestressed pipe carried out pile sinking, take form of construction work by the joint pile sinking, and the pile-sinking method that is adopted comprises hammering method, static pressure method, lash method, water jetting, prebored hole method, middle pick method etc., wherein static pressure method is with the most use.In the present embodiment, adopt static pressure method to carry out pile sinking.

To sum up, before pile for prestressed pipe constructed, in a plurality of the above joint, be positioned at earlier the stake joint bottom seals welding piling bar point of foot.After treating that prestressing pipe pile construction is accomplished, the pile crown of reserving more than 7 on ground.Because, the stake end welding piling bar point sealing stake end of pile for prestressed pipe, and the joints of adjacent two said stake joints adopt welding manner to be connected and sealed, thereby can guarantee effectively that seepage does not take place position while welding when said pile tube stake in-core water filling.

Step 102, survey pipe are installed: said survey pipe 5 is connected to form by a plurality of survey tube segment from bottom to up; And be tightly connected between adjacent two survey tube segment; The survey tube segment that is positioned at foot in many said survey tube segment is that tube segment is surveyed in the bottom and its bottom seals through seal cover; Thereby can effectively guarantee in said survey pipe 5 water filling the time, seepage does not take place.In the present embodiment, said plasticity sleeve pipe is a HPVC pipe (plastic conduit).

The test probe of said slip micrometer is the probe that two ends have spheric probe, and the length of said test probe is identical with spacing between neighbouring two marks; Adorn a LVDT displacement meter and a NTC thermometer in the said test probe.In the present embodiment, said plasticity sleeve pipe is divided into a plurality of plasticity cover tube segment through a plurality of said marks, all connects through said plasticity cover tube segment between neighbouring two marks.

And the installation process of said survey pipe 5 is following:

Step 1021, bottom are surveyed tube segment and are transferred: earlier with said bottom survey tube segment vertically to be positioned over said pile tube stake core directly over; Adopt the mode of continuous water filling in tube segment is surveyed in said bottom again; Tube segment is surveyed in said bottom vertically sink gradually, till said bottom is surveyed height that the tube segment top exceeds said pile tube stake in-core water level and is h; H=30cm～70cm wherein;

In the present embodiment, h=50cm.During practice of construction, can be according to the concrete needs of reality, the numerical value of h is adjusted accordingly in 30cm～70cm scope.

Step 1022, last one are surveyed tube segment and connect height and transfer: the survey tube segment that last need are installed is sealedly attached to have been transferred on the survey tube segment that puts in place this moment; All that this moment, the current survey tube segment of transferring was connected with its underpart are surveyed tube segment and are formed a water-injecting cavity, and all survey tube segment that the current survey tube segment of transferring is connected with its underpart all are coaxial laying; Afterwards; Mode through continuous water filling in said water-injecting cavity; All survey tube segment that the survey tube segment that current need are transferred is connected with its underpart are vertically sunk in the lump gradually, till the height that exceeds said pile tube stake in-core water level until current survey tube segment top of transferring is h.In the present embodiment, h=50cm.

Step 1023, repeating step 1022 repeatedly, all survey the process of transferring of tube segment in accomplishing said survey pipe, and 5 installations are managed in said survey this moment, and the bottom of tube segment and the pig of said pile tube stake core are surveyed in said bottom.

After 5 installations were managed in said survey, water was filled in its inside.

After surveying pipe 5 installations described in the step 1, the height that the top of said survey pipe 5 exceeds pile for prestressed pipe stake top is 8cm～20cm.The mark that is positioned at foot in a plurality of said marks is the bottom mark, and the distance of said bottom mark and said pile tube stake core bottom is d3, wherein 10cm＜d3＜30cm.

In the present embodiment, the height that the top of said survey pipe 5 exceeds 4 tops of pile for prestressed pipe is 10cm.During practice of construction, can be based on concrete needs, the height that survey pipe 5 tops is exceeded 4 tops of pile for prestressed pipe adjusts accordingly.The length of said survey tube segment is 3m～4m.

In the present embodiment, said plasticity sleeve pipe is connected to form by more piece plasticity cover tube segment, and between neighbouring two plasticity cover tube segment mark is installed.Reality connects into the survey tube segment that joint length is 3m～4m with plasticity sleeve pipe and mark earlier before survey pipe 5 is installed in advance.When said survey tube segment is connected in advance; Dock after earlier the joint location of neighbouring two need connection plasticity cover tube segment all being smeared one deck all-purpose adhesive; The joint that the plasticity that adopts adhesive waterproof tape that neighbouring two need are connected is again overlapped between the tube segment seals, and specifically is in the outside adhesive waterproof tape 24-17 lap seal in order that adopts of joint.To sum up, between neighbouring two plasticity cover tube segment, all adopt omnipotent glue-line and adhesive waterproof tape that the joint location between neighbouring two plasticity cover tube segment is carried out waterproofing work in the said survey pipe 5.

In the present embodiment, the quantity of said survey pipe 5 is one.During practice of construction, be not more than the pile for prestressed pipe of Φ 600m for internal diameter, its pile tube stake in-core is installed the quantity of surveying pipe 5 and is one.

In the actual installation process,,, whenever at a distance from 2m～3m a centralizer one being set and surveying pipe 5 and be fixed in the test position that designs in advance along the depth direction of pile for prestressed pipe for guarantee surveying the accuracy of pipe 5 installation sites.Said survey pipe 5 is carried out in the installation process, from the bottom to top a plurality of said centralizers one are installed respectively synchronously.Said centralizer one comprises the collar, in the lower collar under the last collar and along the circumferential direction be connected in the rib frame that a plurality of ribs between the collar and the lower collar are formed, the said structure that goes up the collar and lower collar all identical with size and the two all be level to laying.The structure of a plurality of said ribs is all identical with size; The said internal diameter of going up the collar and lower collar all less than the external diameter of mark and the internal diameter of the two all greater than the external diameter of plasticity sleeve pipe, the spacing between a plurality of said ribs and the said pile for prestressed pipe inside wall is d1, wherein d1=3mm～8mm; The said space D 1=c * d that goes up between the collar and the lower collar ₀, wherein c=1～2, and d ₀Internal diameter for pile for prestressed pipe.

During practice of construction, when the quantity of said survey pipe 5 was many, the structure of many said survey pipes 5 was all identical with size.And when surveying the pipe installation, many said survey pipes 5 are installed synchronously, and the installation progress of many said survey pipes 5 is all identical.The mounting method of many said survey pipes 5 is all identical, and all installs according to the described method of step 1021 to step 1023.

When the internal diameter of pile for prestressed pipe during greater than Φ 600m, the quantity of said survey pipe 5 is many, and many said survey pipes 5 are along the circumferential direction evenly laid.For guaranteeing that many said surveys manage the accuracy of 5 installation sites, many said survey pipes 5 are assembled into one through a plurality of centralizers two of laying from the bottom to top, and many said survey pipes 5 are assembled into one and survey the pipe group.Spacing between neighbouring two said centralizers two is 2m～3m.Said survey pipe group is vertical to the inside center place that is laid in said pile tube stake core under the centralizing function of a plurality of said centralizers two.And many said survey pipes 5 are carried out in the synchronous installation process, from the bottom to top a plurality of said centralizers two are installed respectively synchronously.Because the structure of many said survey pipes 5 is all identical with size, the installation site of a plurality of said mark of then being installed on many said survey pipes 5 10 is all identical, thus in many said survey pipes 5 mark at same depth place on same horizontal plane.

Said centralizer two comprises annulus and the following annulus that is positioned under the annulus; The said annulus of going up is provided with the interior annulus that many said survey pipes 5 of a plurality of confessions pass with following annulus inside, and along the circumferential direction evenly laying and its installation position are corresponding one by one with the installation position of many said survey pipes 5 for a plurality of said interior annulus.Saidly go up that annulus all are laid on the same horizontal plane in annulus and its inner set all, and go up between all set interior annulus of annulus and its inside and all be connected through transverse connection.Annulus all are laid on the same horizontal plane in said down annulus and its inner set all, and all are connected through transverse connection between set all the interior annulus in annulus and its inside down.Said going up between annulus and the following annulus is connected through vertical connector.Said upward annulus is identical with the quantity of many said survey pipes 5 with the quantity of the interior set interior annulus of following annulus, and the said annulus of going up is all identical with the diameter of the interior set interior annulus of following annulus.The internal diameter of annulus is less than external diameter and its external diameter greater than the plasticity sleeve pipe of mark in said.Identical and the two the diameter of the said diameter of going up annulus and following annulus is than the little 3mm～8mm of internal diameter of pile for prestressed pipe.The said space D 2=c * d that goes up between annulus and the following annulus ₀, wherein c=1～2, and d ₀Internal diameter for pile for prestressed pipe.

5 installations are managed in said survey, adopt grouting equipment to inject packing material 12 in the cavity between said pile tube stake core and survey pipe 5 from the bottom to top, and grouting pressure is 0.2MPa ± 0.02MPa.In the present embodiment; Said packing material 12 is for evenly to be mixed by water, cement and the swell soil ratio according to weight ratio 1000 ︰ 1000 ︰ 75; During practice of construction; Can water, cement and bentonitic weight ratio be adjusted accordingly in the scope of 1000 ︰, 600～1200 ︰ 75 according to concrete needs.The swell soil that is adopted is sodium bentonite or calcium-base bentonite.

In the present embodiment, said grouting equipment comprises grouting pump and the Grouting Pipe of joining with grouting pump.Actual when carrying out slip casting, need Grouting Pipe deeply to the pile tube stake core bottom of pile for prestressed pipe, and carry out slip casting from top to bottom, in the slip casting process like this, the water filling of pile tube stake in-core institute is discharged gradually.During practice of construction, before slip casting, also can adopt pumping equipment that the water filling of said pile tube stake in-core institute is all extracted out.

The test philosophy that the present invention adopted all mixes the packing material 4 that forms by water, cement and swell soil is: the admixture of water makes that each component is easy to stir in the packing material 12; Be convenient to packing material 6 and be poured into smoothly in the space between pile for prestressed pipe and the survey pipe 5, guarantee that cement carries out normal hydration reaction; Cement is powdery hydraulicity inorganic coagulation material, is the intensity source of packing material 12, can effectively adjust the mechanical property of packing material 6 through the adjustment cement factor; Swell soil is to be main moisture clay pit with the montmorillonite; Have stronger imbibition property, dispersiveness, suspension and make slurry property; Behind packing material admixture swell soil, possess good mobility, cohesiveness and water retention etc., improved the performance of packing material 12, be convenient to construction and use.In the actual test process, pile body deformation passes to through packing material 12 and surveys pipe 5.

In the test process; Be in when the uniaxial compressive strength of injection packing material 12 between the uniaxial compressive strength of the uniaxial compressive strength of surveying pipe 5 and said pile for prestressed pipe; And inject packing material 12 single shaft pressure-proof elasticity modulus when being between the single shaft pressure-proof elasticity modulus of the single shaft pressure-proof elasticity modulus of surveying pipe 5 and said pile for prestressed pipe, can load in the step 1.

In the present embodiment; Said packing material 12 injected after N days; The uniaxial compressive strength of said packing material 12 is between the uniaxial compressive strength of the uniaxial compressive strength of surveying pipe 5 and pile for prestressed pipe; And inject packing material 12 the single shaft pressure-proof elasticity modulus be between the single shaft pressure-proof elasticity modulus of the single shaft pressure-proof elasticity modulus of surveying pipe 5 and pile for prestressed pipe, adopt said loading equipemtn pile for prestressed pipe to be loaded from top to bottom at this moment; Wherein, N is not less than 14.

Thereby, in the actual test process, after said packing material 12 injects 14 days, just can load.In addition, during actual the test, also can adopt uniaxial compressive strength test to confirm the load time of said loading equipemtn.

In the present embodiment, all the other method steps are all identical with embodiment 1 with technological principle.

The above; It only is preferred embodiment of the present invention; Be not that the present invention is done any restriction, every technical spirit changes any simple modification, change and the equivalent structure that above embodiment did according to the present invention, all still belongs in the protection domain of technical scheme of the present invention.

Claims (10)

1. pile foundation ponding loading test method of separating based on the strain of creeping is characterized in that this method may further comprise the steps:

Step 1, constant load load: the test pile of from top to bottom construction being accomplished (1) loads, and the load that is loaded on test pile (1) the stake top is F _NThe stress that is applied on said test pile (1) the stake top A is the dowel section area of test pile (1) in the formula;

Said test pile (1) is the concrete pile in being laid in the collapsible loess stratum vertically, and test pile (1) leaves pile crown more than ground;

Pile strain value and the test of pile body internal force before step 2, the immersion: when treating test pile (1) settlement stability; Adopt said slip micrometer that the strain value at test pile (1) pile body different depth place is tested, and handle pile body axle power and the pile side resistance that draws preceding test pile (1) the pile body different depth place of immersion based on test result analysis;

Before in the step 1 test pile (1) being loaded, the survey pipe (5) of the said slip micrometer of laying test pile (1) in earlier, said survey pipe (5) is vertically in the pile body that is laid in test pile (1); Said survey pipe (5) is by plasticity sleeve pipe and a plurality of mark that is installed in from the bottom to top on the said plasticity sleeve pipe of the equal opening in two ends are formed up and down; Mark with the ground flush in a plurality of said marks is a mark one; Be positioned in a plurality of said marks said mark one top and with said mark one adjacent mark be the top mark; Said top mark is positioned at demarcates section (3), and the distance between said top mark and test pile (1) the stake top is greater than the external diameter of test pile (1); The sections of said test pile (1) between said top mark and said mark one is for demarcating section (3);

Step 3, immersion and pile strain value test between soaking period: when treating test pile (1) settlement stability, test pile (1) is soaked, it is τ that the pile top load of test pile this moment (1) is kept the load time ₀After the immersion, per interval △ t adopts said slip micrometer that the strain value at test pile (1) pile body different depth place is once tested; Wherein, △ t=24 hour ± 5 hours; And after m the test, the actual measurement strain value at test pile (1) the pile body different depth place in m the different test moment between corresponding acquisition soaking period;

Wherein, m different tests are respectively t constantly from front to back between soaking period ₁, t ₂, t ₃... t _m, the time interval between adjacent two tests constantly in front and back is △ t, and pile top load is kept load time τ ₀Be positioned at test t constantly ₁Before and the time interval between the two be △ t;

Between soaking period, the stress that is applied on said test pile (1) the stake top remains unchanged;

Step 4, a demarcation section actual measurement creep degree function obtain, and its acquisition process is following:

Step 401, the strain of demarcating section between the soaking period calculating of creeping: according to the test result in step 2 and the step 3; Strain value with m between soaking period different tests demarcation section (3) constantly; All behind the strain value of the deduction preceding demarcation section of immersion (3), the strains that obtain m difference test demarcation section (3) constantly under stress

effect are crept;

The strain that step 402, unitstress effect are demarcated section down calculatings of creeping: with stress in the step 401

effect down the strains of m different tests demarcation section (3) constantly creep, convert under the unitstress effect strains that m difference test the demarcation section (3) in the moment into and creep;

Step 403, the match of demarcation section creep degree function: the strains according to m different tests demarcation section (3) constantly under the unitstress effect that is obtained in the step 402 are crept; Adopt polynomial fitting method; Simulate the creep degree function C (t, the τ that demarcate section (3) between soaking period ₀), and said creep degree function C (t, τ ₀) be that test pile (1) is τ in load age ₀The time the creep degree function;

The creep degree function of step 5, arbitrary load age obtains: according to the creep degree function C (t, the τ that simulate in the step 403 ₀), and adopt aging theoretical, nativistic theory or aging and congenital binding isotherm, extrapolate creep degree function C (t, the τ of said test pile (1) when arbitrary load age τ i _i), i=1,2,3 wherein ... M;

When adopting aging theory to calculate, C (t, τ _i)=C (t, τ ₀)-C (τ _i, τ ₀);

When adopting nativistic theory to calculate, C (t, τ _i)=C (t-τ _i+ τ ₀, τ ₀);

It to be aging when calculating when adopting with congenital binding isotherm,

$C(t,{\mathrm{\τ}}_i)=\frac{C(t,{\mathrm{\τ}}_0)-C({\mathrm{\τ}}_i,{\mathrm{\τ}}_0)+C(t-{\mathrm{\τ}}_i+{\mathrm{\τ}}_0,{\mathrm{\τ}}_0)}{2};$

Step 6, the separation back pile strain value of creeping between soaking period and pile body internal force are calculated: with testing m different actual measurement strain value of testing test pile (1) pile body different depth place constantly between the soaking period that draws in the step 3; After all eliminating creep of concrete, obtain the separation back strain value of creeping at m different tests test pile (1) pile body different depth place constantly between soaking period; Simultaneously, corresponding extrapolate eliminate behind the creep of concrete test pile (1) pile body different depth be between soaking period m different tests axle power constantly with creep separate after pile-side negative friction;

Be in any test t constantly for the arbitrary depth z of test pile (1) pile body _nActual measurement strain value ε _n ^*When (z) eliminating creep of concrete,

According to formula ${\mathrm{\ϵ}}_n\left(z\right)=\frac{P_n\left(z\right)}{\mathrm{EA}}={{\mathrm{\ϵ}}_n}^{*}\left(z\right)-\frac{P_0\left(z\right)}{A}C(t_n,{\mathrm{\τ}}_0)-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{{\mathrm{\Δ\; P}}_i\left(z\right)}{A}C(t_n,{\mathrm{\τ}}_i),$ Calculate the arbitrary depth z of test pile (1) pile body and be in any test t constantly _nCreep and separate the back strain value, wherein n is natural number and n≤m; In the formula, ε _n(z) be in test t constantly for test pile (1) pile body depth z after eliminating creep of concrete _nCreep and separate back strain value, ε _n ^*(z) test pile (1) the pile body depth z that draws for test in the step 3 is in test t constantly _nThe actual measurement strain value, P _n(z) be in test t constantly for test pile (1) pile body depth z after eliminating creep of concrete _nPile body axle power, and

$P_n\left(z\right)=P_0\left(z\right)+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ΔP}}_i\left(z\right);$

${\mathrm{\ΔP}}_n\left(z\right)=\frac{1}{1+\mathrm{EC}(t_n,{\mathrm{\τ}}_n)}\left\{E\right[{{\mathrm{A\ϵ}}_n}^{*}\left(z\right)-P_0\left(z\right)C(t_n,{\mathrm{\τ}}_0)-\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{\mathrm{\ΔP}}_i\left(z\right)C(t_n,{\mathrm{\τ}}_i)]-P_0\left(z\right)-\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{\mathrm{\ΔP}}_i\},$

P ₀(z) the preceding pile body axle power of test pile (1) pile body depth z place immersion that draws for analyzing and processing in the step 2, A is the dowel section area of test pile (1), E is the pile concrete modulus of elasticity of test pile (1), C (t _n, τ ₀) be (t, the τ of creep degree function C described in the step 4 ₀) at test moment t _nThe time functional value, C (t _n, τ _i) be (t, the τ of creep degree function C described in the step 5 _i) at test moment t _nThe time functional value, C (t _n, τ _n) be creep degree function C (t, τ _n) at test moment t _nThe time functional value;

Test pile (1) pile body depth z is in test t constantly after waiting to extrapolate the elimination creep of concrete _nAxle power after, also need according to formula Test pile (1) pile body depth z is in test t constantly after calculating the elimination creep of concrete _nPile-side negative friction.

2. according to the described pile foundation ponding loading test method of separating of claim 1 based on the strain of creeping; It is characterized in that: the test pile described in the step 1 (1) is cylindrical stake; And all side excavations of test pile (1) form test pits (2) that the pile foundation ponding loading test is used; Said testing pits (2) is flat hole, and flush at the bottom of the hole in said mark one and said flat hole; Said demarcation section (a 3) arranged outside has a tank (4), and said tank (4) is coaxial laying for cylindrical tank and its with test pile (1);

In the step 3 to test pile (1) when soaking; Adopt pumping system to continue water filling in tank (4); Inject underground water and fill with tank (4) after, overflow to flow into from tank (4) and test pits (2) and freely descend maceration to steep the residing collapsible loess of test pile (1) stratum;

Said pumping system comprises the pipeline that draws water (10) and underground water is delivered to the pumping equipment (7) in the tank (4) through the pipeline that draws water (10); The rear end of the said pipeline that draws water (10) and pumping equipment (7) join, and the front end of the pipeline that draws water (10) extends the bottom land of tank (4) from top to bottom; The height of said tank (4) is not less than the height of said top mark.

3. according to claim 1 or 2 described pile foundation ponding loading test methods of separating based on the strain of creeping, it is characterized in that: the quantity of surveying pipe (5) described in the step 2 is one or more;

When the quantity of said survey pipe (5) was many, the structure of many said survey pipes (5) was all identical with size, and many said survey pipes (5) along the circumferential direction evenly are laid in the test pile (1);

When adopting said slip micrometer that the strain value at test pile (1) pile body different depth place is tested in the step 2; The strain value at many groups of preceding test pile (1) the pile body different depth places of immersion that draw is tested in corresponding acquisition respectively by many said survey pipes (5); After afterwards the strain value at test pile (1) pile body different depth place before the many groups of immersions being averaged, obtain the mean strain value at preceding test pile (1) the pile body different depth place of immersion; Subsequently, based on the mean strain value at test pile (1) pile body different depth place before the immersion that is obtained, extrapolate the pile body axle power and the pile side resistance at preceding test pile (1) the pile body different depth place of immersion;

In the step 3 m time the test after; Many groups test data that corresponding acquisition is drawn by many said survey pipes (5) test respectively, and each organizes the actual measurement strain value that said test data includes m different tests test pile (1) pile body different depth place constantly between soaking period;

The strain value of m different tests demarcation section (3) constantly between soaking period in the step 401, correspondence is respectively the mean strain value that many said survey pipes (5) are tested m different tests demarcation section (3) constantly between the soaking period that draws;

ε described in the step 6 _n ^*(z), test pile (1) the pile body depth z that draws for many said survey pipes (5) test is in test t constantly _nAverage actual measurement strain value.

4. according to the described pile foundation ponding loading test method of separating of claim 2 based on the strain of creeping; It is characterized in that: the bottom of said tank (4) is provided with a plurality of infiltrations hole (13); A plurality of said infiltrations holes (13) along the circumferential direction evenly are laid in the outside all around of test pile (1), and a plurality of said infiltrations holes (13) all are vertically to laying.

5. according to claim 1 or 2 described pile foundation ponding loading test methods of separating based on the strain of creeping; It is characterized in that: when loading, adopt device for measuring force to test pile (1) from top to bottom in the step 1 the said load F that is applied on test pile (1) the stake top _NDetect in real time, and with the testing result synchronous driving to data processor;

When adopting said slip micrometer that the strain value at test pile (1) pile body different depth place is tested in the step 2; The data collecting instrument of said slip micrometer with the test result synchronous driving to data processor; Said data processor carries out analyzing and processing to test result, and corresponding pile body axle power and the pile side friction that draws preceding test pile (1) the pile body different depth place of immersion; And the data collecting instrument of the micrometer of slip described in the step 3; Test pile (1) the pile body different depth that test is drawn is in m different actual measurement strain value synchronous driving constantly to said data processor of testing between soaking period; Said data processor carries out analyzing and processing according to the described method of step 4 to step 6 again, and handled draw eliminate test pile (1) pile body different depth behind the creep of concrete and be between soaking period m different tests creeping constantly and separate after strain value, pile body axle power and pile-side negative friction.

6. according to claim 1 or 2 described pile foundation ponding loading test methods of separating based on the strain of creeping; It is characterized in that: the axle power that also needs in the step 6 to be in m the different test moment between soaking period according to test pile (1) pile body different depth behind the elimination creep of concrete of extrapolating is separated the back pile-side negative friction with creeping, and extrapolates the Depth of Neutral of test pile between soaking period (1).

7. according to claim 1 or 2 described pile foundation ponding loading test methods of separating based on the strain of creeping; It is characterized in that: the test pile described in the step 1 (1) is a bored pile; And behind the stake hole forming of said bored pile; Earlier said survey pipe (5) is installed in the said stake hole, more said bored pile is carried out the concrete spouting construction.

8. according to claim 1 or 2 described pile foundation ponding loading test methods of separating, it is characterized in that: when loading, adopt charger to load test pile (1) from top to bottom in the step 1 based on the strain of creeping; Said charger comprises that two are positioned at the anchoring pile (8) of test pile (1) left and right sides and are erected on the loading equipemtn (9) between two said anchoring piles (8), said loading equipemtn (9) be positioned at test pile (1) directly over.

9. according to claim 1 or 2 described pile foundation ponding loading test methods of separating based on the strain of creeping, it is characterized in that: the test pile described in the step 1 (1) is a pile for prestressed pipe; After treating that said prestressing pipe pile construction is accomplished, in the said pile for prestressed pipe that construction is accomplished, install again and survey pipe (5), and said survey pipe (5) is vertically to the pile tube stake core middle part that is laid in said pile for prestressed pipe; Said top mark is the mark that is positioned at topmost in a plurality of said marks;

After treating said survey pipe (5) installation; Adopt grouting equipment from the bottom to top to the pile tube stake core of said pile for prestressed pipe and survey and inject packing material (12) in the cavity between the pipe (5) again, said packing material (12) is the mixed serum that is uniformly mixed to form according to the ratio of weight ratio 1000 ︰ 600～1200 ︰ 75 by water, cement and swell soil.

10. according to claim 1 or 2 described pile foundation ponding loading test methods of separating based on the strain of creeping, it is characterized in that: a plurality of said marks are even laying in the step 1, and the spacing between neighbouring two said marks is 1m; In the step 3 △ t=24 hour.

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