CN104631252A - Method for controlling cumulative settlement of pile-supported subgrade strengthening pile - Google Patents

Abstract

The invention discloses a method for controlling the cumulative settlement of a pile-supported subgrade strengthening pile. The method comprises the following steps: calculating a dynamic stress attenuating to the upside of a soil arch height by virtue of a Boussinesq's Equation; calculating according to the dynamic stress, a pile spacing and a share ratio of a load of a pile top to obtain the dynamic load above the pile top; calculating according to the weight of a subgrade filling, an upper load of a subgrade and the share ratio of the load of the pile top to obtain a static load above the pile top; calculating according to an ultimate bearing capacity of a pile tip and the static load above the pile top and the dynamic load above the pile top to obtain a cyclic load ratio and a static load ratio of a single pile above the pile top, namely, a thickness of the subgrade and the bearing capacity of the pile tip accord with a requirement in a case that the cyclic load ratio and the static load ratio of the single pile meet a certain condition so that the control for the cumulative settlement of the pile-supported subgrade strengthening pile is completed.

Description

A kind of method controlling pile formula subgrade strengthening stake cumulative settling

Technical field

The present invention relates to a kind of method for designing of roadbed, related in particular to a kind of method controlling pile formula subgrade strengthening stake cumulative settling, controlled differential settlement and the cumulative settling of roadbed by the cumulative settling controlling reinforcing pile.

Background technology

Rigid pile is applied widely in high-speed railway, Reinforcement of Highway, have rigidity large, be out of shape little, convenient, the quality of constructing and be easy to the advantages such as control.This embankment reinforced by stake is called pile formula roadbed.Pile formula roadbed, during runing, is subject to the cyclic loading that train produces.Under cyclic load, the phenomenon of rigid pile and easily generation cumulative settling and bearing capacity change.The thickness of roadbed is an important design objective in high-speed railway subgrade design.At present, Design of High-speed Railway Specification Design is less than according to the dynamic stress decayed to bottom roadbed the thickness that 0.2 times of subgrade selfload stress determines roadbed, and thinks that the dynamic stress attenuation trend of roadbed inside can calculate according to Boussinesq solution.This method for designing does not consider the impact that the inner soil arching effect of pile formula roadbed transmits roadbed inside dynamic stress and the cumulative settling of rigid pile under Long-term Cyclic Loading effect and the phenomenon of bearing capacity change.Existing achievement in research shows, the dynamic stress transmission of soil arching effect on roadbed inside has obvious impact, and its affecting laws and soil arch affect similar on the propagation law of static stress.Under the impact of soil arch, in the native pitch of arch within the scope of road bed, the dynamic stress of roadbed inside separates decay according to Boussinesq; Within the scope of the native pitch of arch, above stake top, the dynamic stress of inside soil body increases progressively with the embankment degree of depth, and between stake, the dynamic stress of top inside soil body then accelerates decay with the roadbed degree of depth.For pile formula roadbed, stake top assume responsibility for most dynamic stress, and can have a huge impact the cumulative settling of rigid pile.The satisfy the need relative settlement of base table layer and the stability of roadbed of sedimentation due to reinforcing pile has larger impact, therefore for the design of pile formula roadbed, must consider the cumulative settling of reinforcing pile under Long-term Cyclic Loading effect.

Existing achievement in research shows when the cyclic loading of single pile is than CLR and dead load 0≤15CLR+5SLR < 3 more satisfied with SLR, and reinforcing pile is without sedimentation or slightly cumulative settling, and within about 10 weeks, reach stable, cumulative settling is less than 0.1 ‰ d.Therefore, as satisfied 0≤15CLR+5SLR < 3, the long-time stability during the operation of pile formula roadbed, safety and comfortableness can be ensured.

Simultaneously the achievement in research bearing ratio in piles and soils that shows to bear responsibility stake the dynamic load share ratio of load and the EBGEO soil arch theory of computation obtain is more consistent.Therefore for the calculating of the inner dynamic stress of pile formula roadbed, the impact considering soil arching effect is needed.Calculate stake bear responsibility load dynamic load can be divided into two calculating: 1, utilize Boussinesq separate calculating the native pitch of arch above dynamic stress; 2, the dynamic load (not considering the decay of dynamic stress in soil arch inside) of load of bearing responsibility according to bearing ratio in piles and soils calculating stake.

Summary of the invention

In order to control the cumulative settling of reinforcing pile under the long-term cyclic load of pile formula roadbed train, solve the problem of pile formula roadbed train operation comfortableness and safety, the object of the present invention is to provide a kind of method controlling pile formula subgrade strengthening stake cumulative settling, be applied to the design of pile formula roadbed.

The technical solution used in the present invention comprises the following steps:

1) the native pitch of arch H of roadbed inside _ebe 0.5 times of pile spacing, be expressed as 0.5s, s is pile cover spacing, is separated the dynamic stress σ calculating and decay to above the native pitch of arch by Bu Xinnaisike (Boussinesq) _d;

Above-mentioned native pitch of arch H _enamely following formulae discovery is adopted:

$H_e=\frac{1}{2}s$

2) according to the above-mentioned dynamic stress σ calculated _dwith pile spacing s, pile top load share ratio E _pcalculate dynamic load P above stake top _d;

3) according to severe γ, the roadbed upper load w of roadbed filling _sand pile top load share ratio E _pcalculate dead load P above stake top _s;

4) according to ultimate bearing capacity of pile tip P _udead load P above the stake top obtained with above-mentioned steps _s, dynamic load P above stake top _dfollowing formulae discovery is adopted to obtain single pile cyclic loading above stake top than CLR and dead load than SLR:

CLR＝P _d/P _u

SLR＝P _s/P _u

The single pile cyclic loading calculated is made to meet the condition of 0≤15CLR+5SLR < 3 than CLR and dead load than SLR, thickness and the bearing capacity of pile tip of roadbed meet the requirements, make roadbed under long-term dynamic loading, the cumulative settling caused due to pile body does not develop, and completes the control to pile formula subgrade strengthening stake cumulative settling.

Described step 2) dynamic load P above king-pile top _dthe following formulae discovery of concrete employing obtains:

P _d＝E _p·s ²·σ _d

Wherein, σ _dfor dynamic stress, s is pile spacing, E _pfor pile top load share ratio.

Described step 3) dead load P above king-pile top _sthe following formulae discovery of concrete employing obtains:

P _s＝E _p·s ²·σ _s

σ _s＝γ·H+w _s

Wherein, γ is the severe of roadbed filling, and H is the thickness of roadbed, w _sfor roadbed upper load, σ _sfor mean stress within the scope of the level single pile of stake top.

Described pile top load share ratio E _pfollowing German reinforced earth specification (EBGEO) soil arch design formulas is adopted to obtain:

$E_p=\frac{s^2\&CenterDot;(\mathrm{\&gamma;}\&CenterDot;H+w_s)-(s^2-a^2)\&CenterDot;[{\mathrm{\&lambda;}}_1^{\mathrm{\&chi;}}\&CenterDot;(\mathrm{\&gamma;}+\frac{w_s}{H})\&CenterDot;(H\&CenterDot;{({\mathrm{\&lambda;}}_1+h_g^2\&CenterDot;{\mathrm{\&lambda;}}_2)}^{-\mathrm{\&chi;}}+H_e\&CenterDot;({({\mathrm{\&lambda;}}_1+\frac{H_e^2\&CenterDot;{\mathrm{\&lambda;}}^2}{4})}^{-\mathrm{\&chi;}}-{({\mathrm{\&lambda;}}_1+H_e^2\&CenterDot;{\mathrm{\&lambda;}}_2)}^{-\mathrm{\&chi;}}))]}{s^2\&CenterDot;(\mathrm{\&gamma;}\&CenterDot;H+w_w)}$

Wherein, χ is a square parameter, λ ₁for pile cover spacing parameter, s is pile spacing, w _sfor roadbed upper load, H is the thickness of roadbed, λ ₂for pile cover arrangement factor, K _critfor intensity parameter, H _efor the native pitch of arch, a is pile cover size.

Described square parameter χ specifically adopts following formulae discovery:

$\mathrm{\&chi;}=\frac{a\&CenterDot;(K_{\mathrm{crit}}-1)}{{\mathrm{\&lambda;}}_2\&CenterDot;s}$

Wherein, s is pile spacing, λ ₂for pile cover arrangement factor, K _critfor intensity parameter, a is pile cover size.

Described pile cover spacing parameter λ ₁the following formulae discovery of concrete employing:

${\mathrm{\&lambda;}}_1=\frac{1}{8}{(s-a)}^2$

Wherein, s is pile spacing, and a is pile cover size.

Described pile cover arrangement factor λ ₂the following formulae discovery of concrete employing:

${\mathrm{\&lambda;}}_2=\frac{s^2+2\&CenterDot;s\&CenterDot;a-a^2}{2\&CenterDot;s^2}$

Wherein, s is pile spacing, and a is pile cover size.

Described intensity parameter K _critthe following formulae discovery of concrete employing:

Wherein, for roadbed filling angle of friction.

The invention has the beneficial effects as follows:

Contemplated by the invention the affecting laws that the inner soil arching effect of pile formula roadbed transmits roadbed inside dynamic stress, consider soil arching effect and can enlarge markedly the dynamic load born above stake top.

Above contemplated by the invention pile formula subgrade strengthening stake, dynamic load is on the impact of reinforcing pile cumulative settling.

Contemplated by the invention the progressions model of pile formula subgrade strengthening stake cumulative settling, and have chosen a kind of sedimentation progressions model the most stable, the safety of roadbed under long-term train cyclic loading effect, stability and comfortableness can be ensured.

Accompanying drawing explanation

Fig. 1 is the principle schematic of the inventive method.

Fig. 2 is the rigid pile three kinds of typical cumulative settling development models under cyclic load that the present invention relates to.

Fig. 3 is the development model of rigid pile cumulative settling under different cyclic loading combines than SLR than CLR and dead load.

In Fig. 1: 1, roadbed, 2, rigid pile, 3, pile cover, 4, soil arch.Roadbed table dynamic stress σ ₀, native pitch of arch place dynamic stress σ _d, stake top plane mean stress σ _s, stake top dead load P _s, stake pushes load P _d, bearing capacity of pile tip P _u, roadbed thickness H, roadbed filling severe γ, native pitch of arch H _e, pile spacing s, pile cover size a, pile body diameter d, roadbed upper load w _s, load width l.

Detailed description of the invention

Below in conjunction with drawings and Examples, the present invention is further illustrated.

As shown in Figure 1,1 is roadbed to the inventive method, and 2 is rigid pile, and 3 is pile cover, and 4 is soil arch; Pile cover 3 is arranged on above each rigid pile 2, roadbed paving 1 on pile cover 3, and above pile cover 3, roadbed 1 inside forms soil arch 4.

Embodiments of the invention detailed process is:

The foundation principle that single pile cyclic loading of the present invention satisfies condition than SLR than CLR and dead load is as follows:

Fig. 2 is rigid pile three kinds of typical cumulative settling development models under cyclic load, and be divided into I type, II type, III type, I type cumulative settling development model is the most stable, is conducive to the cumulative settling controlling pile formula roadbed most;

Table 1 is the conclusion of rigid pile three kinds of cumulative settling development model phenes under cyclic load, and I type cumulative settling development model is the most stable, is conducive to the cumulative settling controlling pile formula roadbed most

According to Fig. 2 and following table 1, the cumulative settling development model of pile formula subgrade strengthening stake should control in I type;

Table 1

Fig. 3 is that different cyclic loading combines the development model of lower rigid pile cumulative settling than CLR and dead load than SLR, as we can see from the figure as satisfied 0≤15CLR+5SLR < 3, the development model of rigid pile cumulative settling is I type, and that therefore chooses that 0≤15CLR+5SLR < 3 calculates as final load satisfies condition.

When meeting 0≤15CLR+5SLR < 3, the thickness of roadbed and bearing capacity of pile tip meet the requirements, make roadbed under long-term dynamic loading, the cumulative settling caused due to pile body does not develop, and can ensure the comfortableness of roadbed under the long-term cyclic load of train and safety.

If do not meet, then the thickness of roadbed and bearing capacity of pile tip undesirable, adjustment above-mentioned parameter, increases the thickness H of roadbed, and the bearing stratum of adjustment stake end changes the ultimate bearing capacity P of stake end _u, pile cover size a, pile cover distance s, until the condition meeting 0≤15CLR+5SLR < 3.

According to certain subgrade construction project background, as specific embodiments of the invention:

1) the concrete background of object of construction production is as follows:

Certain roadbed adopts rigid pile to carry out the reinforcing of roadbed as foundation treatment mode, and wherein rigid pile pile body diameter d is 0.6m, arranged in squares, pile spacing s is 1.8m, is furnished with pile cover above rigid pile, and pile cover shape is square, the width a of pile cover is 1m, bearing capacity of pile tip P _ufor 989.1kN, the thickness of roadbed is 3.2m, and the filler severe γ of roadbed is 20kN/m ³, the angle of friction of filler be 37 °, roadbed upper load w _sfor 20kPa, be strip load, load width is the dynamic stress σ on 1.5m, roadbed top layer ₀for 20kPa.

2) the native pitch of arch H of roadbed inside _ebe 0.5 times of pile cover distance s, calculate native pitch of arch H _efor 0.9m

3) dynamic stress within the scope of road bed to the native pitch of arch separates decay according to Boussinesq, utilizes Boussinesq solution to calculate the dynamic stress σ of Tu Gonggaoduchu _d, calculate the dynamic stress σ above the native pitch of arch _dfor 13.18kPa;

4) bearing ratio in piles and soils E _putilize EBGEO soil arch design formulas to calculate, obtain bearing ratio in piles and soils E _pbe 0.887, do not consider dynamic stress in the native pitch of arch to the decay within the scope of the level of stake top, utilize bearing ratio in piles and soils E _pcalculate stake bear responsibility load dynamic load P _d, stake pushes load P _dfor 37.90kN;

5) according to severe, the roadbed upper load w of roadbed filling _sand pile top load share ratio E _pcalculate dead load P above stake top _s; First calculate stake top level single pile scope mean stress σ _sfor 84kPa, then calculate stake top dead load P _sfor 241.44kN;

6) according to the ultimate bearing capacity of pile tip P obtained by Single pile static load test _udead load P above the stake top obtained with above-mentioned steps _s, dynamic load P above stake top _dobtain single pile cyclic loading above stake top than CLR and dead load than SLR: finally obtaining single pile cyclic loading thus than CLR is 0.038, and obtaining dead load than SLR is 0.244;

7) calculating 15CLR+5SLR is 1.80, meet 0≤15CLR+5SLR < 3, under this project roadbed is subject to long-term train cyclic loading effect during runing, the cumulative settling development model of its reinforcing pile is I type, its cumulative settling can not develop, and can ensure comfortableness and the safety of train operation.

Above-mentioned detailed description of the invention is used for explaining and the present invention is described, instead of limits the invention, and in the protection domain of spirit of the present invention and claim, any amendment make the present invention and change, all fall into protection scope of the present invention.

Claims (8)

1. control a method for pile formula subgrade strengthening stake cumulative settling, it is characterized in that:

1) the native pitch of arch H of roadbed inside _ebe 0.5 times of pile spacing, be expressed as 0.5s, s is pile cover spacing, is calculated the dynamic stress σ decayed to above the native pitch of arch by Boussinesq's formula _d;

2) according to the above-mentioned dynamic stress σ calculated _dwith pile spacing s, pile top load share ratio E _pcalculate dynamic load P above stake top _d;

3) according to severe γ, the roadbed upper load w of roadbed filling _sand pile top load share ratio E _pcalculate dead load P above stake top _s;

4) according to ultimate bearing capacity of pile tip P _udead load P above the stake top obtained with above-mentioned steps _s, dynamic load P above stake top _dfollowing formulae discovery is adopted to obtain single pile cyclic loading above stake top than CLR and dead load than SLR:

CLR＝P _d/P _u

SLR＝P _s/P _u

The single pile cyclic loading calculated is made to meet the condition of 0≤15CLR+5SLR < 3 than CLR and dead load than SLR, thickness and the bearing capacity of pile tip of roadbed meet the requirements, make roadbed under long-term dynamic loading, the cumulative settling caused due to pile body does not develop, and completes the control to pile formula subgrade strengthening stake cumulative settling.

2. a kind of method controlling pile formula subgrade strengthening stake cumulative settling according to claim 1, is characterized in that: described step 2) dynamic load P above king-pile top _dthe following formulae discovery of concrete employing obtains:

P _d＝E _p·s ²·σ _d

Wherein, σ _dfor dynamic stress, s is pile spacing, E _pfor pile top load share ratio.

3. a kind of method controlling pile formula subgrade strengthening stake cumulative settling according to claim 1, is characterized in that: described step 3) dead load P above king-pile top _sthe following formulae discovery of concrete employing obtains:

P _s＝E _p·s ²·σ _s

σ _s＝γ·H+w _s

Wherein, γ is the severe of roadbed filling, and H is the thickness of roadbed, w _sfor roadbed upper load, σ _sfor mean stress within the scope of the level single pile of stake top.

4. a kind of method controlling pile formula subgrade strengthening stake cumulative settling according to claim 1 or 3, is characterized in that: described pile top load share ratio E _pfollowing German reinforced earth specification soil arch design formulas is adopted to obtain:

$E_p=\frac{s^2\&CenterDot;(\mathrm{\&gamma;}\&CenterDot;H+w_s)-(s^2-a^2)\&CenterDot;[{\mathrm{\&lambda;}}_1^{\mathrm{\&chi;}}\&CenterDot;(\mathrm{\&gamma;}+\frac{w_s}{H})\&CenterDot;(H\&CenterDot;{({\mathrm{\&lambda;}}_1+h_g^2\&CenterDot;{\mathrm{\&lambda;}}_2)}^{-\mathrm{\&chi;}}+H_e\&CenterDot;({({\mathrm{\&lambda;}}_1+\frac{H_e^2\&CenterDot;{\mathrm{\&lambda;}}_2}{4})}^{-\mathrm{\&chi;}}-{({\mathrm{\&lambda;}}_1+H_e^2\&CenterDot;{\mathrm{\&lambda;}}_2)}^{-\mathrm{\&chi;}}))]}{s^2\&CenterDot;(\mathrm{\&gamma;}\&CenterDot;H+w_s)}$

Wherein, χ is a square parameter, λ ₁for pile cover spacing parameter, s is pile spacing, w _sfor roadbed upper load, H is the thickness of roadbed, λ ₂for pile cover arrangement factor, K _critfor intensity parameter, H _efor the native pitch of arch, a is pile cover size.

5. a kind of method controlling pile formula subgrade strengthening stake cumulative settling according to claim 4, is characterized in that: described square parameter χ specifically adopts following formulae discovery:

$\mathrm{\&chi;}=\frac{a\&CenterDot;(K_{\mathrm{crit}}-1)}{{\mathrm{\&lambda;}}_2\&CenterDot;s}$

Wherein, s is pile spacing, λ ₂for pile cover arrangement factor, K _critfor intensity parameter, a is pile cover size.

6. a kind of method controlling pile formula subgrade strengthening stake cumulative settling according to claim 4, is characterized in that: described pile cover spacing parameter λ ₁the following formulae discovery of concrete employing:

${\mathrm{\&lambda;}}_1=\frac{1}{8}{(s-a)}^2$

Wherein, s is pile spacing, and a is pile cover size.

7. a kind of method controlling pile formula subgrade strengthening stake cumulative settling according to claim 4, is characterized in that: described pile cover arrangement factor λ ₂the following formulae discovery of concrete employing:

${\mathrm{\&lambda;}}_2=\frac{s^2+2\&CenterDot;s\&CenterDot;a-a^2}{2\&CenterDot;s^2}$

Wherein, s is pile spacing, and a is pile cover size.

8. a kind of method controlling pile formula subgrade strengthening stake cumulative settling according to claim 4, is characterized in that: described intensity parameter K _critthe following formulae discovery of concrete employing:

Wherein, for roadbed filling angle of friction.