CN103205956B - Method for controlling roadbed loading rate by observing pore water pressure - Google Patents
Method for controlling roadbed loading rate by observing pore water pressure Download PDFInfo
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- CN103205956B CN103205956B CN201210569851.9A CN201210569851A CN103205956B CN 103205956 B CN103205956 B CN 103205956B CN 201210569851 A CN201210569851 A CN 201210569851A CN 103205956 B CN103205956 B CN 103205956B
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Abstract
The invention discloses a method for controlling a roadbed loading rate by observing pore water pressure. The method includes the steps: arranging and embedding pore water pressure gauges; connecting each pore water pressure gauge with a measuring device matched with the pore water pressure gauge; drawing a chart indicating the relation between the pore water pressure and time according to the measured relation between the pore water pressure and the time when a roadbed begins to be filled with earth and loaded; selecting two highest peak points on a pore pressure process line during initial loading, and connecting and extending the two highest peak points to serve as an early warning line for the pore water pressure; modifying the early warning line in a static load prepressing period after initial loading; and controlling subsequent earth filling speed according to the modified early warning line. The method avoids adverse effects of factors such as defects of static water pressure definition and difficult accurate quantification of earth filling increment in actual construction on pore water pressure coefficient values, and has the advantages of accuracy, intuition, easiness in operation and the like.
Description
Technical field
The present invention relates to a kind of expressway construction engineering, specifically refer to a kind of by observing pore water pressure to control the method for roadbed loading speed.
Background technology
In expressway construction, utilize pore pressure gauge observation soft foundation weak soil Pore Pressure under imposed load effect to rise by the process of disappearing with controlled loading speed, obtained certain application at present.
Pore water pressure observation is implemented by pore pressure gauge.Hole presses meter kind more, as waterpipe type, pressure measurement tubular type, differential resistance type etc., due to features such as steel chord type pore pressure gauge have good stability, highly sensitive, use is simple, convenient, thereby is widely used.Steel chord type pore pressure gauge component part and operating principle are as follows: steel chord type pore pressure gauge is mainly constructed by permeable stone and pressure sensor two parts and formed: permeable stone material is generally made by silica or rustless metal powder, has very high water permeability.Steel chord type pressure sensor.By Stainless Steel pressure-bearing film, string wire, bracket shell and signal-transmitting cable, formed.Its structure is that one end of a string wire is fixed on to pressure-bearing center membrane, and the other end is fixed on support, and an electromagnetic coil is installed on string wire side, in order to exciting and induction frequencies signal.Steel chord type frequency measurement instrument.For supporting (instrument) equipment of steel chord type pore pressure gauge, with it, collect pore pressure gauge gauge head frequency.
Steel chord type pore pressure gauge bears pressure and makes after film distortion on gauge head pressure-bearing film, make to be fixed on the string wire relaxation of deformation on film, thereby change the natural frequency of string, application string wire frequency meter (plate reading) receives its natural frequency, can try to achieve its active force (pore water pressure) according to following formula.Both sides relation is as follows:
u＝k(f
0 2–f
1 2)………………………………………..(1)
In formula: u is pore water pressure (kPa)
K is constant, is called sensor coefficient, by indoor standardization, is provided;
F
0the natural frequency (Hz) of the lower string wire of zero pressure (atmospheric pressure)
F
1for under pore water pressure effect, string wire natural frequency, reads not string wire natural frequency (Hz) in the same time by the survey of steel chord type frequency measurement instrument and just can try to achieve pore water pressure u (kPa).
Hole can be observed after pressing meter to bury.During observation, press meter H cable center tap to be connected in steel chord type frequency measurement instrument and hole, on steel chord type frequency measurement instrument, demonstrate the natural frequency (Hz) of this (pore pressure gauge) measuring point.By (1) formula, this pore water pressure U (kPa) when this survey is inferior can be tried to achieve, accordingly, pore water pressure U and time t relational process line can be conveniently drawn out.
Due to what cause soft base generation deformation, be excess pore water pressure, therefore also need underground fluctuation in stage situation to observe, to monitoring gained pore water pressure U is revised.Revised pore water pressure is excess pore water pressure u, can draw out as stated above excess pore water pressure graph.
In addition, when carrying out pore water pressure observation, also need to carry out the observation of load increment (thickness h of banketing), for ease of relatively load increment and Super-void Water Pressure fluctuation relation between the two, can be by its compilation on same figure, i.e. load, excess pore water pressure and time relationship graph.Clearly, can qualitative understanding pore water pressure and load relation between the two.But for controlling the speed of banketing, seem unable to do what one wishes from the relation of quantitatively analyzing between the two.
Present stage, adopting pore water pressure is " coefficient is pressed in single-stage hole " and " coefficient is pressed in comprehensive hole " monitoring method to control the method for the speed of banketing.The pore water pressure proposing according to Cape Town (A.W.Skempton) is theoretical, and pore pressure parameter expression formula is:
B
single-stage=Δ u/ Δ P (2)
Comprehensive pore pressure parameter B
comprehensivelyexpression formula is:
B
comprehensively=(U
i-U
0)/Σ P
i(3)
In upper two formulas: △ u---excess pore water pressure increment (kPa);
△ P---load increment (kPa);
U
i---i measuring point pore water pressure (kPa);
U
0---initial pore water pressure (kPa);
∑ △ P
i---be accumulated to the total load (kPa) of i level.
By above-mentioned data substitution (2) (3) formula, can calculate each measuring point loads the phase single-stage hole pressure coefficient and comprehensive hole pressure coefficient in difference.
Coefficient monitor control index and monitoring are pressed in hole: pore pressure parameter monitor control index Duo You designing institute provides in plan: generally pressure coefficient in single-stage hole is 0.6, and it is 0.4 that coefficient is pressed in comprehensive hole.By above-mentioned observation and calculating, its Standard of Monitoring is: coefficient B is pressed in single-stage hole
single-stage=Δ u/ Δ P>=0.6 or when coefficient B is pressed in comprehensive hole
comprehensively=(U
i-U
0)/Σ P
i>=0.4 o'clock, stop loading.Stop carrying rear roadbed when static loading prepressing state, As time goes on, pore water pressure dissipation, the pressure coefficient B of portalling of retrying to obtain
single-stage≤ 0.5, coefficient B is pressed in comprehensive hole
comprehensivelywithin≤0.3 o'clock, can recover to load,
Adopting ventage piezometer to carry out monitoring to roadbed is a kind of new technology occurring last century Mo in China, belongs to stress trajectory.Compare with deformation (sedimentation, the displacement) observation of roadbed routine, its sensitivity is far above the latter.Practice shows, when load is applied on roadbed, just can record the change that pore water pressure occurs.Obviously this is of great benefit to for controlling destabilization of roadbed.The embedding technique of pore pressure gauge has become ripe at present.In addition data acquisition cylinder list and be accurately a large advantage of this technology.
From (2) (3) formula, solve pore pressure parameter and need to obtain excess pore water pressure and its increment △ u, also should obtain load and its increment △ p.In the observation of the soft base of routine, by the pore water pressure total pore space water pressure U measuring that pop one's head in, comprise two partly: i.e. hydrostatic pressure h and by the caused excess pore water pressure u of subsidiary stress (banketing on roadbed) (excess pore-water pressure).Excess pore water pressure expression formula is:
u＝U-h (4)
In formula: u---excess pore water pressure (kPa); H---hydrostatic pressure (is pressed h γ
ωbe converted into kPa); U---total pore space water pressure (kPa); Above-mentioned three elements is in speedway observation, and because being subject to the multifactor restrictions such as geology and geomorphology, construction condition, except total pore space water pressure U can obtain accurately numerical value very much, obtaining of all the other two yuan of numbers all has following some shortcomings part:
The definition defect that a, hydrostatic pressure are calculated
Hydrostatic pressure h is defined as: " water pressure that set point and table depth displacement cause " in < < Standard for fundamental erms of geotechnical engineering > >
[1].It is accurate that this definition is owed:
The soil body in the steady seepage that is located in slope body (as speedway cut and fill section), by this definition, its hydrostatic pressure u=γ
ωh (in formula, h is that the soil body is to slope body table depth displacement).
But, if from this soil body gravitational potential of living in and pressure potential analysis, calculate by simple how much, in above formula, the soil body should be the equipotential lines of this soil body projection h'(h ' the < h on the vertical vertical line of this soil body to table depth displacement) rather than above formula in h.If this steady seepage flow direction and horizon angle are α, its hydrostatic pressure u=γ
ωhcos2 α.Both difference is obvious.
Visible, in < < Standard for fundamental erms of geotechnical engineering, the definition of > > hydrostatic pressure is owed accurately, will directly have influence on the uniqueness of excess pore water pressure calculating.
Hydrostatic pressure observation
How the observation that is all located in visible table roadbed hydrostatic pressure for embankment both sides, arrange water-level observation point in roadbed both sides side slope.According to observed result, extrapolate its phreatic line to roadbed.After this according to two survey time phreatic lines in hole, press measuring point vertically to the difference in change of fixed point to determine the changing value of hydrostatic pressure value.
For both sides, be in the roadbed that pull up on the He Hu pool that communicates with the external world, by the observation to its table elevation, adopt said method to determine that h is feasible.But for roadbed both sides (or a side), there is no visible table (pool, river) section, owing to being subject to highway expropriation of land impact, many observers are arranged on groundwater table test tube from the position of roadbed side slope 1m-3m.
Groundwater table pipe is close to roadbed, affected by roadbed side slope load, and its SEA LEVEL VARIATION has suitable part to be caused by roadbed side slope stress, surely belongs to excess pore water pressure.The part excess pore water pressure in water level test tube of usining, as hydrostatic pressure, has been made notional mistake.If this substitution of above-mentioned observed result (2), (3) formula are calculated to pore pressure parameter, its value must be little, in order to control the speed of banketing, probably jeopardizes roadbed safety.
The calculating of phreatic line
After obtaining roadbed both sides table elevation, carry out the calculating of roadbed phreatic line to determine that water level elevation change location that in Fig. 1, A is ordered is to determine hydrostatic pressure h.
Phreatic line design formulas is many and calculate numerous and diverse.The fringe conditions that each formula has each formula to use, relates to parameter also many.As: Permeability Coefficient of Foundation, roadbed transmission coefficient, pervious foundation thickness, seepage line length, roadbed two side slopes ratios and water level etc.Parameter is more, calculates the error producing also just relatively large.
Load measurement
Load and load increment are one of parameters of calculating pore pressure parameter.Because engineering observes the method that mostly is on-the-spot interim measurement or measures with transportation to determine load increment.Practice shows no matter adopt which kind of method, and the error in measurement of its load increment is common occurrence within the scope of native 2cm～native 4cm: result of calculation has illustrated that load increment error, in the thick impact that judgement produces on monitored results of 1cm scope soil, sees some from this.
The change of pore pressure gauge position
Pore pressure gauge is embedded in weak soil, weak soil must produce sedimentation in consolidation process, certainly, pore pressure gauge position also can change thereupon, and how does its deflection measure? how is fall rate? pore pressure gauge sinks the problems such as impact of pore water pressure value is had not yet to see to data of literatures report so far.It sinks and presses the impact of coefficient not learn on hole.
Summary of the invention
In order to overcome above-mentioned deficiency, the object of the present invention is to provide a kind ofly more to approach true, simple and easy to do, the workable observation pore water pressure that passes through to control the method for roadbed loading speed.
For solving the problems of the technologies described above, the technical solution adopted in the present invention is:
By observation pore water pressure, to control the method for roadbed loading speed, comprise the following steps:
The layout of A, pore pressure gauge and burying underground: in each layout points boring of roadbed, pore pressure gauge is buried underground wherein; At the soil layer of different nature of roadbed, at least arrange a hole pressure meter; Homogeneity Soft Soil Layer is thicker, and meter is pressed in a plurality of holes of equidistant placement.
B, each pore pressure gauge sensing equipment supporting with it is connected, the pressure parameter that sensing equipment transmits in order to receive pore pressure gauge, obtains pore water pressure value by this pressure parameter.
C, roadbed is started to banket in the process loading, by the pore water pressure and the time relationship that record, draw the chart of pore water pressure and time relationship, by the location point of each pore water pressure of the different time in the chart formation hole pressure graph that is connected;
D, in hole during original upload, press on graph and select two peak-peak points, connect and extend, this line is pore water pressure early warning line;
E, the static loading prepressing after original upload completes are in the phase: for pore water pressure, be steady dissipation, get its total squeeze time median as revising early warning line starting point, put the parallel lines of making above-mentioned early warning line be correction early warning line with this; For pore water pressure, be that non-stationary dissipates, get each arithmetic mean of instantaneous value loca of surveying time gained pore water pressure as revising early warning line starting point, with this, put the parallel lines of making above-mentioned early warning line and be correction early warning line;
F, with revised early warning line, control the follow-up speed of banketing: while loading when roadbed is continued to banket, the pore water pressure value recording at each time detecting point is painted on to hole presses on the chart of graph, often measure a pore water pressure value, draw immediately this value in the position of chart, in the time of below early warning line is being revised in the position of pore water pressure value, can continue the loading of banketing; When pore water pressure value approaches, revise early warning line, slow down the loading speed of banketing; When the position of pore water pressure value meets or exceeds correction early warning line, loading stops banketing.
In steps A, described boring adopts the mode of drilled dry, and the spacing between described pore pressure gauge layout points is 2m～3m.
In step B, described pore water pressure is counted steel chord type pore pressure gauge, its supporting sensing equipment is steel chord type frequency measurement instrument, steel chord type frequency measurement instrument is connected with the H cable joint on steel chord type pore pressure gauge, described steel chord type frequency measurement instrument is received in the natural frequency (Hz) of the measuring point of pore pressure gauge transmission, utilizes following formula can try to achieve this pore water pressure when inferior: u=k (f
0 2– f
1 2), in formula: u is pore water pressure (kPa); K is constant, is called sensor coefficient, by indoor standardization, is provided; f
0the natural frequency (Hz) of the lower string wire of zero pressure (atmospheric pressure); f
1for under pore water pressure effect, string wire natural frequency, reads not string wire natural frequency (Hz) in the same time by the survey of steel chord type frequency measurement instrument and just can try to achieve pore water pressure u (kPa).
It during described original upload, is 10～15 days.
Beneficial effect of the present invention is: a, adopt pore water pressure graphical method, inherited all advantages of prior art.Thereby layout, method of installation and the observation procedure of prior art Pore Pressure meter all do not change.Pore water pressure value U and time t that b, utilization observe draw " pore water pressure graph " on computers, and because the pore water pressure U collecting is accurate, thereby the pore water pressure graph of drawing out can reach the effect of " thousand people one figure ".C, on pore water pressure graph, draw " early warning line " with controlled loading speed, have accurately, the feature such as directly perceived, easy operating.On d, pore water pressure graph, draw " early warning line " with controlled loading speed, wherein " early warning line " generation is " get back in practice and go again from practice " Successful Practice with application, and its marrow is " make concrete analyses of concrete problems ".E, owing to affecting, the uncertainty of deformation of ground is too many, with to adopt hyperbolic method to inquire into final settlement the same, determines that a superior in quality early warning line also " needs certain (practice) experience and skill ".This is the weak point of this method.But concerning an engineering, tens at least of design pore water pressure observation point positions, tens at most.As long as several initial holes are pressed to load by this method, perform design, and by design organization construction, all can obtain " early warning line " of fine quality.Just made easy progress from experience later.
Accompanying drawing explanation
Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail:
Fig. 1 is pore water pressure of the present invention and the pore water pressure of time relationship drafting and the curve map of time relationship.
The specific embodiment
By observation pore water pressure, to control the method for roadbed loading speed, comprise the following steps:
The layout of A, pore pressure gauge and burying underground: in each layout points boring of roadbed, pore pressure gauge is buried underground wherein; At the soil layer of different nature of roadbed, at least arrange a hole pressure meter; Homogeneity Soft Soil Layer is thicker, and meter is pressed in a plurality of holes of equidistant placement.Ordinary circumstance pore pressure gauge is to be arranged in place, roadbed axis, and also installation position is adjusted in visual geological condition and designing requirement.Soil layer of different nature is at least arranged a hole pressure meter; As thicker in homogeneity Soft Soil Layer, meter is pressed in a plurality of holes of equidistant placement, and its distance is advisable with 1/2m-3m; Under processing soft soil boundary face, non-Soft Soil Layer also can be arranged a hole pressure meter.The embedding employing boring of pore pressure gauge is buried underground, and boring is advisable with dry drill method.First at the scene measuring pore pressure gauge is numbered after the original frequency of measuring each hole pressure meter, the permeable stone boiling is contained on pore pressure gauge in water, make it simultaneously in the situation that does not depart from water moves down into the hole of filling with clear water, press to after designing requirement elevation+30cm and cable is adjourned outward in side slope observation case.In addition, be anti-this " string hole " to be advisable in " hole one " (meter is pressed in an embedding hole of boring).
B, each pore pressure gauge sensing equipment supporting with it is connected, the pressure parameter that sensing equipment transmits in order to receive pore pressure gauge, obtains pore water pressure value by this pressure parameter.The concrete scheme of this step is: described pore water pressure is counted steel chord type pore pressure gauge, its supporting sensing equipment is steel chord type frequency measurement instrument, steel chord type frequency measurement instrument is connected with the H cable joint on steel chord type pore pressure gauge, described steel chord type frequency measurement instrument is received in the natural frequency (Hz) of the measuring point of pore pressure gauge transmission, utilizes following formula can try to achieve this pore water pressure when inferior: u=k (f
0 2– f
1 2), in formula: u is pore water pressure (kPa); K is constant, is called sensor coefficient, by indoor standardization, is provided; f
0the natural frequency (Hz) of the lower string wire of zero pressure (atmospheric pressure); f
1for under pore water pressure effect, string wire natural frequency, reads not string wire natural frequency (Hz) in the same time by the survey of steel chord type frequency measurement instrument and just can try to achieve pore water pressure u (kPa).
C, as shown in Figure 1, to roadbed, start to banket in the process loading, by the pore water pressure and the pore water pressure of time relationship drafting and the schematic diagram of time relationship that record, the location point of each pore water pressure of the different time in figure is connected and forms hole pressure graph; Pore water pressure observation graphical method is on its plinth of prior art, get rid of complexity and the ambiguity of above-mentioned hydrostatic pressure in observation, calculating, the impact of the factors such as load increment error in measurement, the value U of pore water pressure accurately and the time t that directly utilize observation to obtain, draw pore water pressure and time relationship graph (being U～t curve) on computers.During original upload, (also claim first order loading duration) and seem particularly important.Practice by Xingning～the She nationality, distributed over Fujian, Zhejiang, Jiangxi and Guangdong river speedway, Guangzhou～Wuzhou speedway, Yunfu～Luoding speedway draws: first order loading duration was advisable with 10～15 days.During original upload, (also claim first order loading duration), therefore the thickness that bankets is many can carry out loading continuously fast in " the roadbed limit banket elevation ", load soil thick by designing requirement with 25cm/ layer.Load increase causes pore water pressure to rise, and pore water pressure rises and causes weak soil pore water to be discharged, and weak soil pore water is discharged the fixed bearing capacity of foundation soil that causes of soft soil generation and risen to convention.Because pore water is discharged and to be caused soil solidifying to need the regular hour could be complete, i.e. so-called " time effect ", therefore, after completing first order loading, requirement stops carrying the one week left and right time of precompressed and loads together operation under carrying out again, to improve " limit banket high level " of ground, for loading, subordinate prepares.
D, in hole during original upload, press on graph and select two peak-peak points, connect and extend, this line is pore water pressure early warning line, in Fig. 1, as the straight line of solid line, is pore water pressure early warning line;
In practical operation, utilize computer can easily obtain pore water pressure and time relationship graph, close examination pore pressure graph, gets two peak points and connects and extend to X, and AX line is the pore water pressure early warning line of this measuring point.
E, the static loading prepressing after original upload completes are in the phase: for pore water pressure, be steady dissipation, get its total squeeze time median as revising early warning line starting point, put the parallel lines of making above-mentioned early warning line be correction early warning line with this; For pore water pressure, be that non-stationary dissipates, get each arithmetic mean of instantaneous value loca of surveying time gained pore water pressure as revising early warning line starting point, with this, put the parallel lines of making above-mentioned early warning line and be correction early warning line, in Fig. 1, the correction early warning line that is pore water pressure as the straight line of dotted line.
Pore water pressure early warning line is the product that the first order loads practice, and its line slope reflects that load increase is coadapted with the raising of ground bearing capacity in this grade of loading procedure faithfully.Certainly, this coadapted relation loads and plays surely certain directive function the imminent second level.But exist the quantitatively variation of size.For caution's sake, be necessary pore water pressure early warning line to be revised.
The modification method of pore water pressure early warning line: get the first order load stop carrying after a measured pore water pressure add U
1before loading to the second level, observation station obtains U
2arithmetic mean of instantaneous value as the starting point O that revises early warning line, calculating formula is (U
1+ U
2)/2, the O of take makes ray OY//AX as starting point, and the OY line of doing is the early warning line after being corrected.Using this pore water pressure early warning line loading as follow-up one-level.In practice of construction, owing to being subject to the many factors such as weather, stock ground, machinery allotment, duration, during stopping carrying, also often there is loading fragmentary, discontinuous form.This loading causes pore water pressure and dissipation to be reflected on the pressure conditional curve figure of hole and is fluctuation excessively on sawtooth pattern shape.But as long as the overall horizontal or downward trend of this curve all can adopt this method to revise described early warning line.
F, with revised early warning line, control the follow-up speed of banketing: while loading when roadbed is continued to banket, the pore water pressure value recording at each time detecting point is painted on to hole presses on the chart of graph, often measure a pore water pressure value, draw immediately this value in the position of chart, in the time of below early warning line is being revised in the position of pore water pressure value, can continue the loading of banketing, if between the two apart from larger, can appropriateness increase banket speed to urge the duration; When pore water pressure value approaches, revise early warning line, slow down the loading speed of banketing; When the position of pore water pressure value meets or exceeds correction early warning line, the loading that stops banketing, after stopping loading, pore water pressure U can dribble under normal circumstances, when it drops to " early warning line " below, can recover to load; Otherwise, stop carrying standing during the abnormal conditions that go up not down of pore water pressure value U.Now, the data of other observation point (as sedimentation, displacement) that can arrange with same section is carried out network analysis, to determine that whether " off-load back-pressure " to ensure safety.
Case history:
Wide Chinese parasol tree speedway 18 contract section k118+250～k118+360 section left sides are massif, and right side is soft foundation, belongs to typical cut and fill section, and this section adopts 3 settlement plates, 2 displacement skirt piles and 2 pore water pressures that roadbed is loaded and monitored.Designing requirement monitor control index is: single-stage hole presses coefficient < 0.6, comprehensive hole to press coefficient < 0.4, sedimentation < every day 10mm, horizontal movement < every day can load during 5mm.
In the present embodiment, can find out March 18 from line chart is buckled in hole, two hole measuring point pore water pressures have all surpassed early warning line.Should assign and stop carrying notice, be prudent meter, simultaneously also for the reliability for check " early warning line ", so to the same day rate of settling press coefficient to calculate with hole, it the results are shown in Table 2 and table 3.
Table 2 instruction stops carrying phase settlement observation data summary sheet
Table 3 instruction stops carrying phase single-stage pore pressure parameter computational chart
As can be seen from the table: March 18, the rate of settling was 7.0mm/d, it is 0.579 that coefficient is pressed in single-stage hole, and it is 0.149 that coefficient is pressed in comprehensive hole.All be less than the monitor control index of designing requirement, therefore assign, do not stop carrying notice.Construction corps had filled again one deck soil routinely on that night.
Observation on March 19 pore water pressure value still surpasses " early warning line ", the rate of settling approaches designing requirement monitor control index 10mm/d and reaches 9.0mm/d, single-stage hole presses coefficient to surpass designing requirement monitoring to refer to that 0.60 has reached 0.697, and only to press one of coefficient be 0.159 in monitor control index 0.4 in comprehensive hole.Assigned routinely " stopping carrying notice ".
Found that this section of roadbed gutter inwall produces crack on March 23, gutter bottom protrusion (report designing institute to become afterwards and more taked the engineering measures such as berm with superloading).Illustrate that " " assigning is timely, and the highly sensitive feasibility of loading speed being monitored in row change observation, " early warning line " of stress trajectory is also described simultaneously to stop carrying notice for this.
This period of later stage loads and fails for a long time to carry out because of affected by change in the work, and when having built rear recovery when berm with superloading and loading (genus the 6th phase loading), for working to tight deadlines, construction corps has taked rapid loading method, from 4 to 9 August, loads 1.58m in six days.In this period, the measured rate of settling rises to 13.5mm/d from the 11.0mm/d on August 6 always, single-stage pore pressure parameter also from August 7 all over 0.6, when maximum, reach 0.84.Above-mentioned observation is all over design pore water pressure monitor control index 0.6.Should assign routinely " stopping carrying notice ".But, on pore water pressure curve map, reflect each measuring point hole voltage crest value all from " early warning line " very away from, the maximum pore water pressure value that when maximum pore water pressure value and the first order load therebetween, a is ordered is almost located in the same horizontal line.Therefore do not assign " stopping carrying notice ".Not only for having increased precompressed, roadbed lasts, also for the time has been won on roadbed unloading in the future, build road surface.After being open to traffic, observed result more than a year shows, this time rapid loading does not produce any disease to roadbed, shows that it is successful that this engineering adopts pore water pressure graphical method to control the practice that roadbed loads.
In a word; although the present invention has enumerated above-mentioned preferred embodiment, should illustrate, although those skilled in the art can carry out various variations and remodeling; unless such variation and remodeling have departed from scope of the present invention, otherwise all should be included in protection scope of the present invention.
Claims (4)
1. by observing pore water pressure to control a method for roadbed loading speed, it is characterized in that: comprise the following steps:
The layout of A, pore pressure gauge and burying underground: in each layout points boring of roadbed, pore pressure gauge is buried underground wherein; At the soil layer of different nature of roadbed, at least arrange a hole pressure meter; Homogeneity Soft Soil Layer is thicker, and meter is pressed in a plurality of holes of equidistant placement;
B, each pore pressure gauge sensing equipment supporting with it is connected, the pressure parameter that sensing equipment transmits in order to receive pore pressure gauge, obtains pore water pressure value by this pressure parameter;
C, roadbed is started to banket in the process loading, by the pore water pressure and the time relationship that record, draw the chart of pore water pressure and time relationship, by the location point of each pore water pressure of the different time in the chart formation hole pressure graph that is connected;
D, in hole during original upload, press on graph and select two peak-peak points, connect and extend, this line is pore water pressure early warning line;
E, the static loading prepressing after original upload completes are in the phase: for pore water pressure, be steady dissipation, get its total squeeze time median as revising early warning line starting point, put the parallel lines of making above-mentioned early warning line be correction early warning line with this; For pore water pressure, be that non-stationary dissipates, get each arithmetic mean of instantaneous value loca of surveying time gained pore water pressure as revising early warning line starting point, with this, put the parallel lines of making above-mentioned early warning line and be correction early warning line;
F, with revised early warning line, control the follow-up speed of banketing: while loading when roadbed is continued to banket, the pore water pressure value recording at each time detecting point is painted on to hole presses on the chart of graph, often measure a pore water pressure value, draw immediately this value in the position of chart, in the time of below early warning line is being revised in the position of pore water pressure value, can continue the loading of banketing; When pore water pressure value approaches, revise early warning line, slow down the loading speed of banketing; When the position of pore water pressure value meets or exceeds correction early warning line, loading stops banketing.
2. according to claim 1 by observing pore water pressure to control the method for roadbed loading speed, it is characterized in that: in steps A, described boring adopts the mode of drilled dry, and the spacing between described pore pressure gauge layout points is 2m～3m.
3. according to claim 1 by observing pore water pressure to control the method for roadbed loading speed, it is characterized in that: in step B, described pore water pressure is counted steel chord type pore pressure gauge, its supporting sensing equipment is steel chord type frequency measurement instrument, steel chord type frequency measurement instrument is connected with the H cable joint on steel chord type pore pressure gauge, described steel chord type frequency measurement instrument is received in the natural frequency (Hz) of the measuring point of pore pressure gauge transmission, utilizes following formula can try to achieve this some pore water pressure at this moment:
u=
k(
f 0 2–
f 1 2), in formula:
ufor pore water pressure (kPa);
kfor constant, be called sensor coefficient, by indoor standardization, provided;
f 0natural frequency (Hz) for the lower string wire of zero pressure (atmospheric pressure);
f 1for under pore water pressure effect, string wire natural frequency, reads not string wire natural frequency (Hz) in the same time by the survey of steel chord type frequency measurement instrument and just can try to achieve pore water pressure u(kPa).
4. according to claim 1 by observing pore water pressure to control the method for roadbed loading speed, it is characterized in that: in described step D, during original upload, be 10～15 days.
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| CN201210569851.9A CN103205956B (en) | 2012-12-25 | 2012-12-25 | Method for controlling roadbed loading rate by observing pore water pressure |
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| CN201210569851.9A Active CN103205956B (en) | 2012-12-25 | 2012-12-25 | Method for controlling roadbed loading rate by observing pore water pressure |
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| CN115031889B (en) * | 2022-04-21 | 2024-08-20 | 中国公路工程咨询集团有限公司 | Pore water pressure monitoring method and device, electronic equipment and storage medium |
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| CN1587523A (en) * | 2004-09-21 | 2005-03-02 | 武汉理工大学 | Dynamic simulation design method for highway soft foundation treatment construction |
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| CN101358449B (en) * | 2008-09-11 | 2010-09-01 | 中国科学院武汉岩土力学研究所 | Pore water pressure measuring device in foundation stabilization zone |
| JP5476528B2 (en) * | 2009-08-25 | 2014-04-23 | 学校法人立命館 | Soil moisture level detector and slope failure prediction system using the same |
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