TEST METHOD FOR FRICTION RESISTANCE AT INNER AND OUTER SIDEWALLS OF PIPE PILE

Abstract

The invention relates to a method to test friction resistance at inner and outer sidewalls of pipe pile through in-situ test. The method comprises embedding a strain sensor at inner or outer sidewalls of pipe pile to measure strain variation generating on pipe pile body under the action of load; carrying out static load test with the soil plug remaining in the pipe pile to obtain the strain variation ε.sub.p1j,i of the pipe pile body at the i.sup.th soil layer; taking out the soil plug remaining in the pipe pile and carrying out static load test to obtain the strain variation ε.sub.p2j,i of the pipe pile body at the i.sup.th soil layer; and obtaining the friction respectively at the outer and inner sidewalls of the pipe pile at the i.sup.th soil layer according to the measured strain variation, ε.sub.p1j,i and ε.sub.p2j,i.

Claims

1. A test method for friction resistance of inner and outer sidewalls of pipe pile, comprising: a. embedding a strain sensor at inner or outer sidewalls of pipe pile to measure strain variation generating on pipe pile body under the action of load; b. carrying out a static load test with a soil plug remaining in the pipe pile: applying a P.sub.1j load to the upper end of the pipe pile to obtain a strain variation ε.sub.p1j,i of the pipe pile body at the i.sup.th soil layer; c. taking out the soil plug remained in the pipe pile and carrying out static load test: applying a P.sub.2j load onto the upper end of the pipe pile and measuring a strain variation ε.sub.p2j,i of the pipe pile body at the i.sup.th soil layer by the strain sensor; d. according to the measured strain variation ε.sub.p1j,i and ε.sub.p2j,i, the following are obtained: the friction at outer sidewall of the pipe pile at the i.sup.th soil layer is $f_{s.Math..Math.1.Math.j,i}=\frac{{\mathrm{ER}}_{1.Math..Math.i}}{4.Math..Math.\Delta .Math..Math.H_i}.Math.{\mathrm{.Math.}}_{p.Math..Math.2.Math..Math.j,i};$ and the friction at inner sidewall of the pipe pile(1) at the i.sup.th soil layer is $f_{s.Math..Math.2.Math..Math.j,i}=\frac{E}{4.Math.R_{2.Math..Math.i}.Math.\Delta .Math..Math.H_i}\left[\left(R_{1.Math..Math.i}^2-R_{2.Math..Math.i}^2\right).Math.{\mathrm{.Math.}}_{p.Math..Math.1.Math.j,i}-R_{1.Math..Math.i}^2.Math.{\mathrm{.Math.}}_{p.Math..Math.2.Math..Math.j,i}\right];$ wherein, E represents modulus of elasticity of the pipe pile; ΔH.sub.i represents the thickness of the soil at the i.sup.th soil layer; R.sub.1i and R.sub.2i represent the external and internal diameters of the pipe pile at the i.sup.th soil layer respectively.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0007] FIG. 1 is the schematic diagram of static load test with a soil plug remaining in a pipe pile.

[0008] FIG. 2 is the schematic diagram of static load test with a soil plug taken out of a pipe pile.

DETAILED DESCRIPTION OF THE INVENTION

[0009] In the embodiment, the strain sensor 2 including a strain meter, a stress gauge and a distributed optical fiber is embedded at the inner or the outer sidewall of the pipe pile 1. The strain sensor 2 can be embedded either before the pipe pile 1 is driven, or after the pipe pile 1 is driven after embedded parts are embedded into the pipe pile 1. The strain sensor 2 shall be embedded before static load test is performed on the pipe pile 1.

[0010] After the pipe pile 1 with built-in strain sensor 2 is driven into the soil layer 4, the sand layer 5 and the bearing stratum 6, then the two static load tests are conducted on the pipe pile 1 with static load test equipment.

[0011] In the first static load test, the soil plug 3 is remained in the pipe pile 1. A P.sub.1j load is applied onto the upper end of the pipe pile 1 (see FIG. 1). In the second static load test, the soil plug 3 is taken out of the pipe pile 1, namely, there is no soil in the pipe pile 1. P.sub.1j load is applied onto the upper end of the pipe pile 1 (see FIG. 2). The two static load tests are applied with the same hierarchical-loading and load size.

[0012] In the embodiment, assuming the elasticity modulus of the pipe pile 1 is E(kPa), the thickness of the i.sup.th soil layer is ΔH.sub.i(m), the external and internal diameters of the pipe pile (1) at the i.sup.th soil layer are R.sub.1i(m) and R.sub.2i(m) respectively.

[0013] In the first static load test, the total sidewall resistance of each soil layer under the combined action of the soil of outer and the inner sidewalls of the pipe pile is calculated as per Formula (1)

[00003]$\begin{array}{cc}{R}_{1.Math..Math.i}.Math.f_{s.Math..Math.1.Math.j,i}+R_{2.Math..Math.i}.Math.f_{s.Math..Math.2.Math.j,i}=\frac{E\left(R_{1.Math..Math.i}^2-R_{2.Math..Math.i}^2\right).Math.R_{1.Math..Math.i}}{4.Math..Math.\Delta .Math..Math.H_i}.Math.{\mathrm{.Math.}}_{p.Math..Math.1.Math.j,i}.& \left(1\right)\end{array}$

[0014] In the second static load test, the outer sidewall resistance of each soil layer under the action of the outer sidewall soil of the pipe pile 1 is calculated as per Formula (2)

[00004]$\begin{array}{cc}{f}_{s.Math..Math.1.Math.j,i}=\frac{{\mathrm{ER}}_{1.Math..Math.i}}{4.Math..Math.\Delta .Math..Math.H_i}.Math.{\mathrm{.Math.}}_{p.Math..Math.2.Math.j,i}.& \left(2\right)\end{array}$

[0015] After Formula (2) is substituted into Formula (1), the inner sidewall resistance of each soil layer is calculated as per Formula (3)

[00005]$\begin{array}{cc}{f}_{s.Math..Math.2.Math.j,i}=\frac{\mathrm{.Math.}}{4.Math.R_{2.Math..Math.i}.Math.\Delta .Math..Math.H_i}\left[\left(R_{1.Math..Math.i}^2-R_{2.Math..Math.i}^2\right).Math.{\mathrm{.Math.}}_{p.Math..Math.1.Math..Math.j,i}-R_{1.Math..Math.i}^2.Math.{\mathrm{.Math.}}_{p.Math..Math.2.Math.j,i}\right].& \left(3\right)\end{array}$

[0016] In Formula (1)˜Formula (3), ε.sub.p1j,i is the strain variation of the pile body of the pipe pile 1 at the i.sup.th soil layer under load effect of the j.sup.th grade in the first static load test. ε.sub.p2j,i is the strain variation of the pile body of the pipe pile 1 at the i.sup.th soil layer under load effect of the j.sup.th grade in the second static load test; f.sub.s1j,i is the outer sidewall friction resistance (kPa) of the pipe pile 1 at the i.sup.th soil layer under load effect of the j.sup.th grade in the second static load test: f.sub.s2j,i is the inner sidewall friction resistance (kPa) of the pipe pile 1 at the i.sup.th soil layer under load effect of the j.sup.th grade.

[0017] The principles of this embodiment are as follows: the first static load test is performed on the pipe pile 1 by use of the strain sensor 2 to test and calculate the total sidewall resistance of each soil layer under the combined action of the outer and inner sidewall soil of the pipe pile 1.

[0018] The soil plug 3 is taken out of the pipe pile 1, there is no soil mass in the pipe pile, namely, no inner sidewall friction resistance would generate in the pipe pile 1. Then, the second static load test is performed for the pipe pile 1 by use of the strain sensor 2 embedded in the pipe pile 1 to test and calculate the outer sidewall friction resistance of each soil layer only under the action of outer sidewall soil of the pipe pile.

[0019] The inner sidewall friction resistance of each soil layer can be obtained by deducting the outer sidewall resistance of each soil layer in the second static load test from the total sidewall resistance of each soil layer in the first static load test, thereby obtaining the inner sidewall and outer sidewall friction resistance of the pipe pile at each soil layer.