CN104196060B - CFG pile composite roadbed rubber spacer static load testing device and method - Google Patents

Abstract

The invention provides a CFG pile composite roadbed rubber spacer static load testing device and method. The method comprises the steps that according to the embankment design condition, the punching shear failure angle method is adopted to calculate loads of embankment filling acting on piles and soil between the piles respectively, and pile soil bearing loads and the pile soil stress ratio are obtained; differential settlement of the piles upwards piercing into the spacer amount and differential settlement of the piles upwards piercing into composite foundation pile soil are respectively calculated, the pile piercing amount is comprehensively determined, and according to the table 1, rubber spacers are selected. Arranging is carried out according to the CFG pile composite roadbed rubber spacer static load testing device, and the steps of gradation loading, steady judgment, final load control, data recording and the like are carried out reference to existing specifications and design. According to the device and method, rubber spacers are determined in a mode that load-bearing compression deformation of the rubber spacers is close to the loads, borne by pile bodies, in the actual station, of the upward piercing amount of the spacer amount, a load transfer mechanism of the actual working condition can be simulated, the aim that embankment loads are distributed by the rubber spacers is achieved, and the pile soil stress ratio conforming to the reality can be achieved.

Description

CFG stake composite road bed rubber spacer test for static load apparatus and method

Technical field

The present invention relates to a kind of geotechnical engineering test for static load technological means, being specifically related to a kind of for testing embankment flexible foundation CFG pile composite foundation bearing capacity test method and device.

Background technology

Existing embankment flexible load Bearing Capacity of Composite Foundation test for static load method is mainly tested with reference to the clause of " building foundation treatment technical specification " (JGJ79-2012) Appendix B, and without special roadbed load bearing capacity technical norms for measurement.Specification (JGJ79-2012) is mainly for the test of bearing capacity technology of house construction engineering rigid foundation, and the load transfer law that rigid foundation and embankment flexible foundation are built in room is not quite similar.Main manifestations is: stake, native settlement difference cause composite foundation rigid pile to produce the phenomenon of upwards thrusting bed course, and produce with negative friction.Under embankment loading, rigid pile all has upper thorn phenomenon, causes pile-soil stress less, generally reaches 10 ~ 20; And rigid foundation rigid pile is built in room and supreme thorn phenomenon, pile-soil stress is larger, is generally more than 20.Therefore the CFG pile composite foundation test of bearing capacity technology of inventing a kind of applicable embankment is imperative.

Laying 100 ~ 150mm sand cushion under existing composite foundation test for static load technology employing load flat board, theoretical according to K.V.Terzaghi slide plane elasticity " centronucleus ", if set CFG stake footpath as 0.2 meter, sand cushion angle of internal friction is 35 degree, and calculating elasticity " centronucleus " minimum height values is 140 millimeters.Therefore lay thin sand cushion and be difficult to simulate the actual condition upwards thrusting bed course of stake.If increase the thickness of sand cushion, testing site is difficult to compacting, load the lateral flow that also can cause sand grains, rigidity and the thickness of its bed course can not be ensured, be used for embankment load CFG pile composite foundation test for static load according to existing test for static load method and certainly will cause larger error.The method of laying rubber spacer under adopting bearing plate solves upper thorn phenomenon and the pile-soil stress assignment problem of rigid pile, meets the load transfer law of embankment flexible foundation rigid pile, can reach test purpose.

Summary of the invention

The present invention seeks to for the deficiencies in the prior art, providing a kind of for testing embankment CFG pile composite foundation bearing capacity test for static load method and device.

The present invention is achieved through the following technical solutions:

A kind of CFG stake composite road bed rubber spacer test for static load device, comprise following ingredient: counter-force test block, brace summer, dynamometer, reaction beam, displacement meter, jack, datum line beam, rubber pad, bearing plate, earth pressure gauge, CFG test pile, wherein, described CFG test pile upper end coaxially arranged bearing plate, rubber pad, jack, reaction beam successively from bottom to top; Described bearing plate sole arrangement earth pressure gauge; Displacement meter arranged by described rubber pad; Coaxially arranged dynamometer between described jack and reaction beam; Described reaction beam is arranged counter-force test block; Counter-force test block corner is supported in ground by brace summer; Described datum line beam is symmetricly set in bearing plate both sides.

The planar dimension of rubber pad of the present invention is equal with bearing plate planar dimension.

The bearing plate side of being plate of the present invention or plectane.

A kind of method for the composite road bed rubber spacer test for static load of CFG stake of the present invention, comprises the following steps:

The first step, calculates pile-soil stress when stake penetration amount, selects table to choose rubber pad according to the composite road bed test for static load rubber pad of CFG stake;

Second step, arrange CFG stake composite road bed rubber spacer test for static load device, described CFG stake composite road bed rubber spacer test for static load device comprises and forming with lower part:

Counter-force test block, brace summer, dynamometer, reaction beam, displacement meter, jack, datum line beam, rubber pad, bearing plate, earth pressure gauge, CFG test pile, wherein, described CFG test pile upper end coaxially arranged bearing plate, rubber pad, jack, reaction beam successively from bottom to top; Described bearing plate sole arrangement earth pressure gauge; Displacement meter arranged by described rubber pad; Coaxially arranged dynamometer between described jack and reaction beam; Described reaction beam is stacked counter-force test block; Counter-force test block corner is supported in ground by brace summer; Described datum line beam is symmetricly set in bearing plate both sides;

3rd step, carries out hierarchical loading to the test pile arranged by second step;

4th step, the displacement in record the 3rd step corresponding to every grade of load, stress ratio;

5th step, according to the data obtained in the 4th step, determines load classification, sentences steady standard, carries control eventually;

6th step, evaluate pile body carrying quality, whether CFG pile composite foundation test index bearing capacity, sedimentation, stress ratio three indexs meet specification and designing requirement.

In the first step of the present invention, according to embankment design condition, adopt " punching shear failure angle " method calculating embankment filled soil to act on the load of stake and inter-pile soil respectively, obtain stake soil and bear load and stress ratio.

In the first step of the present invention, stake is thrust method for determination of amount and is: calculate the relative settlement that bed course amount, compound foundation pile soil are upwards thrust in stake respectively, the value of both contrasts, according to the principle that both are equal in theory, if when both calculating gained difference is less than 15% of its average, getting its average is stake penetration amount, otherwise redesigns bed course parameter.

The design formulas of stress ratio of the present invention is as follows:

n＝p _p/p _s

Wherein: p _p---stake top stress, unit: kPa;

P _s---with the resistance to shear of soil at same plane place, stake top, unit: kPa.

Stake of the present invention is upwards thrust bed course amount and is obtained by elastic deformation index calculate during CFG stake top unit pressure, and the design formulas that bed course amount is upwards thrust in stake is as follows:

Δ ₁＝C ₁×p _p

Wherein: p _p---stake top stress, unit: kPa;

C ₁---the deflection of bed course is thrust in stake, unit: m/kPa.

The relative settlement of compound foundation pile soil of the present invention is born frictional resistance elastic and plastic properties domain tyeory by punching shear failure angle theory and Pile side soil and is calculated, and the design formulas of the relative settlement of compound foundation pile soil is as follows:

${\mathrm{\Δ}}_2=\frac{1}{E_s}{\∫}_0^{z_m}{p}_s{e}^{-\mathrm{Az}}\mathrm{dz}$

Wherein: E _s---soil body modulus of compressibility, unit: MPa;

Z _m---negative frictional resistance siding-to-siding block length, unit: m;

A---calculating parameter.

The present invention adopts technique scheme, and compared with prior art tool has the following advantages:

The invention provides a kind of applicable embankment CFG pile composite foundation test for static load method, develop the CFG pile composite foundation test for static load technology conformed to embankment actual loading transport mechanism, for setting up special embankment composite foundation test for static load specification based theoretical." punching shear failure angle " method of employing, the quick stake soil that calculates shares load, as settlement calculation initial load, avoids complicated iterative computation.The invention provides discrete stake soil for " cell cube " method, set up the design formulas in negative frictional resistance elastic and plastic properties district, calculate the relative settlement Δ of compound foundation pile soil ₂, bed course amount Δ is upwards thrust in contrast stake ₁, comprehensively determine a penetration amount Δ _p, and the method for rubber pad is chosen in conjunction with stress ratio n, when the composite road bed test for static load of CFG stake, for different embankment, bedding design parameter, the rubber pad choosing proper stiffness replaces traditional system sand bed course.By the stress ratio data verification of field measurement, the stake soil load transfer mechanism of the realistic operating mode of this technology.

Accompanying drawing explanation

Fig. 1 is CFG stake of the present invention composite road bed rubber spacer test for static load device schematic diagram;

Fig. 2 is the schematic flow sheet for CFG stake composite road bed rubber spacer test for static load method of the present invention;

Fig. 3 is the stressed diagram of test pile;

Fig. 4 is punching shear failure angle force analysis diagram;

Fig. 5 is bed course carrying slide plane schematic diagram;

Fig. 6 is that die-cut force analysis figure is pushed up in stake;

Fig. 7 is bed course, stake soil plastic zone calculates diagram;

Fig. 8 is native unit force analysis schematic diagram;

In Fig. 1,1, counter-force test block; 2, brace summer; 3, dynamometer; 4, reaction beam; 5, displacement meter; 6, jack; 7, datum line beam; 8, rubber pad; 9, bearing plate; 10, earth pressure gauge; 11, CFG test pile;

In Fig. 3,4: θ is punching shear failure angle; σ ₁for large main stress bar; σ ₃for minor principal stress; Ab limit is large main stress bar σ ₁acting surface; Ac limit is minor principal stress σ ₃acting surface; Ad limit is die-cut aa of stake ₁while be effect of stress face, stake top; β is Tai Shaji elastic kernel base angle, i.e. aa ₁with ab angle; In Fig. 5: δ _maxfor plastic zone height; 2r _pfor stake diameter; 2b is stake process width; H _cfor cushion thickness;

In Fig. 6: p _cfor the normal stress on die-cut ad; T _cfor the shear stress on die-cut ad; P _dbe the soil pressure that elastic kernel ab limit is born, G is add ₁a ₁the bed course in region and the deadweight of the soil body;

In Fig. 7: Z ₁for above plastic zone maximum height δ is pushed up in stake _max; Z ₂for bed course apical side height; Z ₃for base surface height; Z ₄for plastic zone depth capacity below stake top;

In Fig. 8: σ _sfor soil unit normal stress; τ _sfor cell cube shear stress.

Detailed description of the invention

Below in conjunction with accompanying drawing, technical solution of the present invention is described in detail, but protection scope of the present invention is not limited to described embodiment.

As shown in Figure 1, the invention discloses a kind of CFG stake composite road bed rubber spacer test for static load device, comprise following ingredient: counter-force test block 1, brace summer 2, dynamometer 3, reaction beam 4, displacement meter 5, jack 6, datum line beam 7, rubber pad 8, bearing plate 9, earth pressure gauge 10, CFG test pile 11, wherein, described CFG test pile 11 upper end coaxially arranged bearing plate 9, rubber pad 8, jack 6, reaction beam 4 successively from bottom to top; Described bearing plate 9 sole arrangement earth pressure gauge 10; Displacement meter 5 arranged by described rubber pad 8; Coaxially arranged dynamometer 3 between described jack 6 and reaction beam 4; Described reaction beam 4 arranges counter-force test block 1; Counter-force test block 1 four jiaos is supported in ground by brace summer 2; Described datum line beam 7 is symmetricly set in bearing plate 9 both sides.

Preferably, rubber pad 8 planar dimension of the present invention is with bearing plate 9, and rubber pad 8 thickness is chosen by table 1; Bearing plate 9 can by the current specifications side of being defined as plate or plectane.

Preferably, in device of the present invention, displacement meter 5 has 4, and range is 50mm, and precision is 0.01mm; Earth pressure gauge 10 has 5, dynamometer 4, and range can be determined according to the load applied, and datum line beam 7 has 2, requires to be symmetrically arranged in bearing plate 9 both sides with reference to current specifications.

In this testing arrangement, replace traditional sand cushion with rubber pad 8 and carry out CFG stake roadbed composite foundation test for static load.The thickness of rubber pad 8 presses the stake penetration amount Δ of theory calculate _pdetermine with stress ratio n, namely rubber pad 8 determination with the compressive strain of rubber spacer load-bearing and actual condition pile body load-bearing upwards penetration deformation feature match for foundation, reach rubber pad to absorb in stake for the purpose of thorn amount, and then simulation actual condition load transfer mechanism.The behavior of mechanics of rubber pad 8 is chosen, in table 1.

Table selected by the composite road bed test for static load rubber pad of table 1CFG post

As shown in Figure 2, present invention also offers a kind of method for the composite road bed rubber spacer test for static load of CFG stake, comprise the following steps:

The first step, calculates stress ratio n and stake penetration amount Δ _p, choose rubber pad according to table 1.

In the step first step of the present invention, according to embankment design condition, adopt " punching shear failure angle " method calculating embankment filled soil to act on the load of stake and inter-pile soil respectively, obtain stake soil and bear load and stress ratio n.

In the step first step of the present invention, stake penetration amount Δ _pdefining method be: respectively calculate stake upwards thrust bed course amount Δ ₁, compound foundation pile soil relative settlement Δ ₂, contrast Δ ₁, Δ ₂value, according to both equal in theory principles, if calculate both gained difference when being less than 15% of its average, getting its average is stake penetration amount Δ _pas rubber pad rigidity selection standard; Otherwise suggestion redesigns bed course parameter, with reach solve bed course can not too soft also can not the object of too hard problem.

In the method for the invention, adopt " punching shear failure angle " method calculating embankment filled soil to act on the load of stake and inter-pile soil respectively, the theoretical basis of calculating that acquisition stake soil bears load and stress ratio n is as follows:

The determination of 1.CFG stake " punching shear failure angle "

During embankment loading, when the soil body of stake top certain limit is in plastic limit state, Tai Shaji slide plane peaks.If pile body upwards potential die-cut crossing with K.V.Terzaghi slide plane.As shown in Figure 3.In the abc of helix region (IIth district), ab limit is large main stress bar σ ₁acting surface, ac limit is minor principal stress σ ₃acting surface, die-cut ad of stake and large main stress bar σ ₁the angle of acting surface be ( ).

Punching shear failure angle, i.e. punching shear failure angle θ:

Cause

If substrate is completely coarse, then

In formula, ---soil body angle of internal friction;

β---Tai Shaji elastic kernel base angle, i.e. aa ₁with ab angle.

The value of concrete punching shear failure angle θ, can be determined by test.

2. destroying slide plane by Terzaghi is log spiral, and as Fig. 5, its equation is:

Plastic zone maximum height δ _maxfor:

In formula, δ _max---plastic zone height, unit m;

θ ₁---the angle of any point d in logatithmic spiral and limit line ad and ab;

R ₀---ab edge lengths, unit m;

R _p---stake radius, unit m;

---soil body angle of internal friction.

3. stress ratio calculates

The region add that die-cut of angle of flare and Tai Shaji slide plane surround ₁a ₁for research object, force analysis as shown in Figure 6.For convenience of calculation, being similar to and getting region height is δ _max.Tai Shaji " elastic kernel " ab limit is by large main stress bar σ ₁.

In formula, N _q---the bearing capacity factor of rough base completely;

R _p---stake radius, unit: m;

In Fig. 3, ac limit minor principal stress:

Normal stress p on die-cut ad _cwith shear stress T _cbe respectively:

$p_c=\frac{1}{2}({\mathrm{\σ}}_1+{\mathrm{\σ}}_3)+\frac{1}{2}({\mathrm{\σ}}_1-{\mathrm{\σ}}_3)\cos 2\mathrm{\α}---\left(6\right)$

$T_c=\frac{1}{2}({\mathrm{\σ}}_1-{\mathrm{\σ}}_3)\sin 2\mathrm{\α}---\left(7\right)$

In formula, if angle die cutting θ=25 °,

By the symmetry of beaer, vertical applied force equilibrium system, can be reduced to two dimensional analysis.

2T _ccosθδ _max-2p _cδ _maxtanθ+γ(H+h _c-δ _max)-2r _pp _p＝0 (8)

In formula, H---depth of fill, unit: m;

H _c---bed course height, unit: m;

P _p---stake top stress, unit: kPa.

γ---soil body severe, unit: kN/m ³

mp _p+(1-m)p _s＝γ(H+h _c) (9)

In formula, m---compound foundation pile replacement ratio;

P _s---with the resistance to shear of soil at same plane place, stake top, unit kPa; Other symbol is the same.

Therefore can p be tried to achieve _p, p _s, and then can stress ratio be obtained

n＝p _p/p _s(10)

In formula, p _p---stake top stress, unit: kPa;

P _s---with the resistance to shear of soil at same plane place, stake top, unit: kPa.

According to above theoretical foundation and the method for the invention first step, provide following embodiment: (1) embankment filled soil parameter: severe γ _t=20kN/m ³, angle of internal friction modulus of pressure E _t=30MPa, poisson's ratio u _c=0.35, depth of fill H=4m.

(2) bedding design parameter: severe γ _c=20kN/m ³, angle of internal friction modulus of pressure E _t=50MPa, poisson's ratio u _c=0.3, thickness H _c=0.3m, C ₁vertical thorn people amount for when stake top unit pressure acts on bed course: C ₁=2.6 × 10 ^-5m/kPa.

(3) CFG stake parameter: Modulus of pressure E _p=18GPa, stake radius r _p=0.2m, pile spacing 2m, replacement ratio m=0.028, the long 10m of stake.

(4) inter-pile soil parameter is as shown in table 2 below:

Table 2 inter-pile soil parameter

According to existing embankment, the soil body, bed course, pile parameter, calculated by following steps:

1. the punching shear failure angle of bed course solves:

By bed course parameter: H _c=0.3m, completely coarse by substrate, have:

Obtained by formula (1), (2): 15 °≤θ≤40 ° are now got θ=25 ° and calculated.

2. r _p=0.2m, is obtained by formula (3): δ _max=624mm

3. a top stress: obtain by formula (4) ~ (8):

$T_c=\mathrm{\τ}=\frac{1}{2}({\mathrm{\σ}}_1-{\mathrm{\σ}}_3)\sin 2\mathrm{\α}=5.08p_s$

p _c＝9.15p _s

P _p=6p _s+ 185 substitute into (9) formula obtains

p _s＝56kpa，p _p＝545kPa

During embankment height 4m, pile top load reaches 545kPa, stress ratio:

Bed course amount Δ is upwards thrust in stake of the present invention ₁by elastic deformation index C during CFG stake top unit pressure ₁calculate.According to bed course mechanical index C ₁calculate stake and thrust bed course amount:

Δ ₁＝C ₁×p _p＝2.6×545＝14.2mm

The relative settlement Δ of compound foundation pile soil of the present invention ₂by " punching shear failure angle ", theoretical and Pile side soil is born frictional resistance " elastic and plastic properties district " theory calculate and is obtained, theoretical foundation and computational methods as follows:

1. the calculating of following plastic zone, a top degree of depth

Under embankment loading, pile body has the phenomenon of upper thorn bed course, and plastic zone appears in stake top certain limit.As shown in Figure 7, plastic zone z ₃z ₄, elastic region z ₄z _m.Suppose that elastic region inside sliding block linearly transmits, plastic zone side friction reaches the limit values τ _u, according to experimental data or experience, the relative displacement of concrete material stake soil elastic limit is 1 ~ 2mm; The contraposition of plastic limit phase

Moving is 2.0 ~ 5.0mm; The displacement of slippage limit relative is δ _u=5 ~ 7.5mm.

Theoretical according to Berrum, stake side hinders

In formula, τ _sa---Pile side soil side friction, unit: kPa;

K ₀---Pile side soil coefficient of earth pressur at rest;

σ _sz---the vertical stress of the soil body, unit: kPa.

Cohesive soil gets k ₀=0.55;

With reference to Fig. 5, if stake process width range is 2b, stake diameter 2r _p, from the angle that load transmits, if apart from distance r place of pile center side frictional resistance equation be:

${\mathrm{\τ}}_{\mathrm{sr}}=\frac{{\mathrm{\τ}}_{\mathrm{sa}}}{1-{\mathrm{\β}}_c}[1-{\mathrm{\β}}_c{e}^{{\mathrm{\β}}_c(\frac{r}{r_p}-1)}]---\left(12\right)$

In formula, τ _sr---apart from pile-soil interface r place soil body shear stress, unit: kPa;

τ _sa---pile-soil interface place side friction, unit: kPa;

R _p---stake radius, unit: m;

β _c---calculating parameter, determined by stake footpath and single pile process range.

From formula (12): as r=b,

If 2b=2m, 2r _p=0.4m, b/r _p=5: β _c=0.3 (13)

Apart from pile center r place (r _p≤ r≤b) fetch earth unit drdz, as shown in Figure 8, can obtain formula (14) by earth stress analysis.

$\begin{array}{c}({\mathrm{\σ}}_s+d{\mathrm{\σ}}_s)[\mathrm{\π}{(r+\mathrm{dr})}^2-{\mathrm{\πr}}^2]-{\mathrm{\σ}}_s[\mathrm{\π}{(r+\mathrm{dr})}^2-{\mathrm{\πr}}^2]-{2\mathrm{\πr\τ}}_s\mathrm{dz}+\\ 2\mathrm{\π}(r+\mathrm{dr})({\mathrm{\τ}}_s+{\mathrm{d\τ}}_s)\mathrm{dz}=0\end{array}---\left(14\right)$

Abbreviation is: $\frac{d{\mathrm{\σ}}_s}{\mathrm{dz}}+\frac{1}{r}{\mathrm{\τ}}_s+\frac{\∂{\mathrm{\τ}}_s}{\∂r}=0---\left(15\right)$

(14) formula can be written as:

$\frac{d{\mathrm{\σ}}_{\mathrm{sz}}}{\mathrm{dz}}+\frac{{\mathrm{\τ}}_{\mathrm{sa}}}{1-{\mathrm{\β}}_c}[\frac{1-{\mathrm{\β}}_c{e}^{{\mathrm{\β}}_c(\frac{r}{r_p}-1)}}{r}+\frac{{\mathrm{\β}}_c^2}{r_p}{e}^{{\mathrm{\β}}_c(\frac{r}{r_p}-1)}]=0---\left(16\right)$

(16) formula is abbreviated as: $\frac{d{\mathrm{\σ}}_{\mathrm{sz}}}{\mathrm{dz}}+A{\mathrm{\σ}}_{\mathrm{sz}}=0---\left(17\right)$

Wherein, $A=\frac{k_0\tan \mathrm{\φ}}{1-{\mathrm{\β}}_c}[\frac{1-{\mathrm{\β}}_c{e}^{{\mathrm{\β}}_c(\frac{r}{r_p}-1)}}{r}+\frac{{\mathrm{\β}}_c^2}{r_p}{e}^{{\mathrm{\β}}_c(\frac{r}{r_p}-1)}]---\left(18\right)$

Work as r=r _ptime, σ _sa=p _se ^-Az(19)

Below neutral point: ${\mathrm{\σ}}_{\mathrm{sz}}=p_s{e}^{-A{z}_m}{e}^{A(z-z_m)}---\left(20\right)$

A certain plane place, plastic zone, the resistance of stake side reaches capacity, pile-soil relative displacement:

$\begin{array}{c}\mathrm{\Δ}{w}_1={\∫}_{r_p}^b\frac{{\mathrm{\τ}}_{\mathrm{sr}}}{G_s}\mathrm{dr}={\∫}_{r_p}^b\frac{{\mathrm{\τ}}_u}{G_s(1-{\mathrm{\β}}_c)}[1-{\mathrm{\β}}_c{e}^{{\mathrm{\β}}_c(\frac{r}{r_p}-1)}]\mathrm{dr}\\ =\frac{{\mathrm{\τ}}_u}{G_s(1-{\mathrm{\β}}_c)}[b-r_p{e}^{{\mathrm{\β}}_c(\frac{b}{r_p}-1)}]\end{array}---\left(21\right)$

In formula, Δ w ₁---plastic zone stake soil relative deformation value, unit: m;

G _s---soil body modulus of shearing, MPa; Other symbol is the same.

2 elastic regions and neutral point z _mcalculate:

Due to etc. heavy face place stake soil without relative displacement, then in elastic region, the difference of the native vertical deformation of stake is relative displacement, makes Δ w ₂=1mm establishes a side resistance along the long linear distribution of stake.The elastic region depth bounds z solved _m:

$\frac{1}{E_s}{\∫}_0^{z_m-z_4}d{\mathrm{\σ}}_s-\frac{1}{E_p}{\∫}_0^{z_m-z_4}d{\mathrm{\σ}}_p=0---\left(22\right)$

In formula, σ _s---the stress of the soil body, unit: kPa;

σ _p---the stress in corresponding degree of depth stake cross section, unit: kPa.

For pile element body, have:

A _pσ _p+A _pdσ _p＝A _pσ _p+γ _pA _pdz+2πaτ _sadz (23)

In formula, A _p---the section area of pile body, unit: m ²;

τ _sa---pile-soil interface side friction, unit: kPa; Other symbol is the same.

To pile body decrement Δ _phave: $d{\mathrm{\Δ}}_p=\frac{r_p{\mathrm{\γ}}_p+2{\mathrm{\τ}}_{\mathrm{sa}}}{r_p{E}_p}\mathrm{dz}---\left(24\right)$

In formula, γ _p---the unit weight of pile body, unit: kN/m ³;

E _p---the modulus of pile body, unit: MPa; Other symbol is the same.

In like manner, the soil of stake process range is considered as integral unit, then has:

A _sdσ _s+A _sσ _s＝A _sσ _s+2πaτ _sadz (25)

To soil body decrement Δ _shave: $d{\mathrm{\Δ}}_s=\frac{2m{\mathrm{\τ}}_{\mathrm{sa}}}{r_p{E}_s(1-m)}\mathrm{dz}---\left(26\right)$

In formula, γ _s---the unit weight of the soil body, unit: kN/m ³;

E _s---soil body modulus of compressibility, unit: MPa;

The replacement ratio of m---compound foundation pile.

A _s---single pile processing area, other symbol is the same.

Ignore the compression of CFG stake, elastic region pile side friction presses the distribution of line shape:

$\begin{array}{c}\mathrm{\Δ}{w}_2={\mathrm{\Δ}}_s={\∫}_0^{z_m-z_4}\frac{2m{\mathrm{\τ}}_u}{r_p{E}_s(1-m)}(1-\frac{z}{z_m})\mathrm{dz}\\ =\frac{2m(1-\frac{z}{z_m}){\mathrm{\τ}}_u}{r_p{E}_s(1-m)}[z_m-z_4-\frac{{(z_m-z_4)}^2}{2z_m}]\end{array}---\left(27\right)$

Namely $\mathrm{\Δ}{m}_2=\frac{2m(1-\frac{z}{z_m}){\mathrm{\τ}}_u}{r_p{E}_s(1-m)}[z_m-z_4-\frac{{(z_m-z_4)}^2}{2z_m}]---\left(28\right)$

In stake, thorn amount is neutral point within the scope of stake top, the relative deformation of stake soil.

${\mathrm{\Δ}}_2=\frac{1}{E_s}{\∫}_0^{z_m}{p}_s{e}^{-\mathrm{Az}}\mathrm{dz}---\left(29\right)$

The relative settlement of 3 compound foundation pile soil calculates

When concrete material pile-soil relative displacement reaches 2.0 ~ 5.0mm, the soil body is in plastic state, and the resistance of stake side reaches τ _u, now get 3mm and calculate.

By b=1m, r _pduring=0.2m, β _c=0.3, E _s=3.8MPa

Substitute into formula (21) to obtain: solve: τ _u=8.94kPa

R=r _ptime, obtained by formula (18):

$A=\frac{k_0\tan \mathrm{\φ}}{1-{\mathrm{\β}}_c}[\frac{1-{\mathrm{\β}}_c{e}^{{\mathrm{\β}}_c(\frac{r}{r_p}-1)}}{r_p}+\frac{{\mathrm{\β}}_c^2}{r_p}{e}^{{\mathrm{\β}}_c(\frac{r}{r_p}-1)}]=0.87$

${\mathrm{\τ}}_u=0.2\×55\×e^{-0.87z_4}=8.94\mathrm{kPa}$

Solve: z ₄=0.26m

Make stake soil elastic limit relative displacement Δ w ₂=1mm, if the resistance of stake side is along the long linear distribution of stake.Obtained by formula (28):

$\mathrm{\Δ}{w}_2=\frac{2m(1-\frac{z}{z_m}){\mathrm{\τ}}_u}{r_p{E}_s(1-m)}[z_m-z_4-\frac{{(z_m-z_4)}^2}{2z_m}]=0.001$

Solve and obtain z _m=3m, namely negative frictional resistance siding-to-siding block length is approximate gets: z _m=3m.

Pile-soil relative displacement, namely the relative settlement of compound foundation pile soil is:

$\begin{array}{c}{\mathrm{\Δ}}_2=\frac{1}{E_s}{\∫}_0^{z_m}{p}_s{e}^{-\mathrm{Az}}\mathrm{dz}\\ =\frac{55}{3.8}{\∫}_0^{0.26}{e}^{-0.87z}\mathrm{dz}+\frac{44.7}{3.8}{\∫}_{0.26}^3{e}^{-0.87z}\mathrm{dz}\\ =03.1\mathrm{mm}\end{array}$

Bed course amount Δ is upwards thrust in Comprehensive Correlation stake ₁the relative settlement Δ of=14.2mm and compound foundation pile soil ₂=13.1mm, both differences are 1.1mm, are less than 15% of average.Therefore get Δ _p=13.7mm, according to table 1, selects the test for static load that the thick rubber pad of 40mm fills for this CFG.

The method of the invention second step is exactly that test pile is good according to Plant arrangement of the present invention.3rd step of the present invention carries out hierarchical loading to the test pile arranged by second step with reference to existing specification.

The method of the invention the 4th step: the displacement in record the 3rd step corresponding to every grade of load, stress ratio.

The method of the invention the 5th step: according to the data obtained in the 4th step, with reference to existing shape specification and the classification of designing requirement determination load, sentences steady standard, eventually year control etc.;

The method of the invention the 6th step: evaluate pile body carrying quality, whether CFG pile composite foundation test index bearing capacity, sedimentation, stress ratio three indexs meet current specifications and designing requirement.

One group of result of the test utilizing a kind of CFG stake of the present invention composite road bed rubber spacer test for static load device to carry out testing is provided in the present invention, as described below:

Arranged in the manner shown in fig. 1 by test pile 11, test Protonation constant, sentence references specification (JGJ79-2012) such as steady method or the execution of local code, soil pressure applies test data in table 3 with load.

A table 3 soil force rate field test results

Stake top stress/kpa	Average soil pressure/kpa	Stress ratio/n
			31.4587764	16.823586	1.869920979
102.733632	25.90021002	3.966517334
			199.1374785	35.9161605	5.544509094
361.2363264	49.14507786	7.350407042
			508.930578	60.60621836	8.39733268

When fieldtesting results shows pile top load 508.93kPa, stress ratio n=8.4, sedimentation is 18.82mm, reaches embankment composite foundation test for static load theory expectation effect, actual measurement stress ratio n and theoretical value substantially identical, other meets design requirement as bearing capacity, sedimentation index.

Above-described embodiment is illustrative principle of the present invention and effect thereof only, but not for limiting the present invention.Any person skilled in the art scholar all without prejudice under spirit of the present invention and category, can modify above-described embodiment or changes.Therefore, have in art usually know the knowledgeable do not depart from complete under disclosed spirit and technological thought all equivalence modify or change, must be contained by claim of the present invention.

Claims (9)

1. a CFG stake composite road bed rubber spacer test for static load device, it is characterized in that, comprise following ingredient: counter-force test block (1), brace summer (2), dynamometer (3), reaction beam (4), displacement meter (5), jack (6), datum line beam (7), rubber pad (8), bearing plate (9), earth pressure gauge (10), CFG test pile (11), wherein, described CFG test pile (11) upper end coaxially arranged bearing plate (9) successively from bottom to top, rubber pad (8), jack (6), reaction beam (4), described bearing plate (9) sole arrangement earth pressure gauge (10), described rubber pad (8) is arranged displacement meter (5), coaxially arranged dynamometer (3) between described jack (6) and reaction beam (4), described reaction beam (4) is arranged counter-force test block (1), counter-force test block (1) corner is supported in ground by brace summer (2), described datum line beam (7) is symmetricly set in bearing plate (9) both sides.

2. a kind of CFG stake according to claim 1 composite road bed rubber spacer test for static load device, is characterized in that, the planar dimension of rubber pad (8) is equal with bearing plate (9) planar dimension.

3. a kind of CFG stake according to claim 1 composite road bed rubber spacer test for static load device, is characterized in that, described bearing plate (9) is square plate or plectane.

4., for a method for the composite road bed rubber spacer test for static load of CFG stake, it is characterized in that, comprise the following steps:

The first step, calculates stress ratio n and stake penetration amount Δ _p, select table to choose rubber pad (8) according to the composite road bed test for static load rubber pad of CFG stake;

Second step, arrange CFG stake composite road bed rubber spacer test for static load device, described CFG stake composite road bed rubber spacer test for static load device comprises and forming with lower part:

Counter-force test block (1), brace summer (2), dynamometer (3), reaction beam (4), displacement meter (5), jack (6), datum line beam (7), rubber pad (8), bearing plate (9), earth pressure gauge (10), CFG test pile (11), wherein, described CFG test pile (11) upper end coaxially arranged bearing plate (9), rubber pad (8), jack (6), reaction beam (4) successively from bottom to top; Described bearing plate (9) sole arrangement earth pressure gauge (10); Described rubber pad (8) is arranged displacement meter (5); Coaxially arranged dynamometer (3) between described jack (6) and reaction beam (4); Described reaction beam (4) is arranged counter-force test block (1); Counter-force test block (1) corner is supported in ground by brace summer (2); Described datum line beam (7) is symmetricly set in bearing plate (9) both sides;

3rd step, carries out hierarchical loading to the test pile arranged by second step;

4th step, the displacement in record the 3rd step corresponding to every grade of load, stress ratio;

5th step, according to the data obtained in the 4th step, determines load classification, sentences steady standard, carries control eventually;

6th step, evaluate pile body carrying quality, whether CFG pile composite foundation test index bearing capacity, sedimentation, stress ratio three indexs meet specification and designing requirement.

5. a kind of method for the composite road bed rubber spacer test for static load of CFG stake according to claim 4, it is characterized in that, in the described first step, according to embankment design condition, " punching shear failure angle " method of employing calculates the load that embankment filled soil acts on stake and inter-pile soil respectively, obtains stake soil and bears load and stress ratio n.

6. a kind of method for the composite road bed rubber spacer test for static load of CFG stake according to claim 4, is characterized in that, in the described first step, and stake penetration amount Δ _pdefining method be: respectively calculate stake upwards thrust bed course amount Δ ₁, compound foundation pile soil relative settlement Δ ₂, contrast Δ ₁, Δ ₂value, according to both equal in theory principles, if calculate both gained difference when being less than 15% of its average, getting its average is stake penetration amount Δ _p, otherwise redesign bed course parameter.

7. a kind of method for the composite road bed rubber spacer test for static load of CFG stake according to claim 5, it is characterized in that, the design formulas of stress ratio n is as follows:

n＝p _p/px

Wherein: p _p---stake top stress, unit: kPa;

P _s---with the resistance to shear of soil at same plane place, stake top, unit: kPa.

8. a kind of method for the composite road bed rubber spacer test for static load of CFG stake according to claim 6, it is characterized in that, bed course amount Δ is upwards thrust in stake ₁by elastic deformation index C during CFG stake top unit pressure ₁calculate, bed course amount Δ is upwards thrust in stake ₁design formulas as follows:

Δ ₁＝C ₁×p _p

Wherein: p _p---stake top stress, unit: kPa;

C ₁---the deflection of bed course is thrust in stake, unit: m/kPa.

9. a kind of method for the composite road bed rubber spacer test for static load of CFG stake according to claim 6, is characterized in that, the relative settlement Δ of compound foundation pile soil ₂bear frictional resistance elastic and plastic properties domain tyeory by punching shear failure angle theory and Pile side soil to calculate, the relative settlement Δ of compound foundation pile soil ₂design formulas as follows:

Wherein: E _s---soil body modulus of compressibility, unit: MPa;

Z _m---negative frictional resistance siding-to-siding block length, unit: m;

A---calculating parameter.