Abstract
Based on the shear displacement method, theoretical research on the load transfer relation of squeezed branch pile is established. In combination with the nonlinear relation of the interaction between piles and soil, the hyperbolic function is used to describe the pile tip, pile skin, and branch. The theoretical method of the load transfer is improved, and the expression of the load transfer coefficient of these three parts is given. Finally, the applicability of the theoretical method is verified by the model test of homogeneous soil and the field test of stratified soil. The verification results show that the theoretical calculation method of the squeezed branch single‐pile bearing capacity based on the shear displacement method can better calculate the ultimate load in practical engineering applications.
Highlights
E expanded branch can bear more loads, and the damage of the squeeze branch pile is mainly due to the shear failure of the soil under the branch or the failure of the soil at the pile end, which is different from the conventional bearing capacity design method. e side resistance of the squeezed branch pile is limited by the branch resistance, and the pile foundation will completely fail after the expanded body is damaged. erefore, this paper establishes the loadsettlement calculation theory of squeezed branch pile based on the shear displacement method
As shown in equations (1) and (2), Randolph and Wroth [16] put forward the influence radius rm 2.5Hρm (1 − ]); H is the depth of the calculated section. ρm is the correction coefficient of finite-depth soil; ρm is taken as 1 in the homogeneous soil layer; ] is Poisson’s ratio of the soil at the side of the pile; τ0(z) is the shear force of the pile-soil contact surface at depth z; and Gs is the shear modulus of the soil
In the formula, cb is the cohesive force of the pile tip soil, qb is the average effective compressive stress on the side of the pile tip plane, and Nc and Nq are the bearing capacity coefficients of the pile. e calculation is shown in the following formula, where φ is the angle of the failure surface of the pile tip under the ultimate load and the range from soft clay to compact sand is 60° to 105°, where c is the soil gravity on the side of the pile and φ is the effective internal friction angle of the soil
Summary
The bearing theory of the shear displacement method proposes that the soil around the pile undergoes shear deformation with the settlement of the pile, and the shear deformation is transferred from the radius r0 of the pile to the influence radius rm, and equation (1) represents the transfer relationship of shear stress τ(z) in the radial direction, and equation (2). Represents the elastic relationship between shear stress τ(z) and shear strain in the soil at the side of the pile: τ(z) τ0(z) r0 , rm (1). Equation (4) takes an element of a single pile for force balance analysis, and the relationship between the pile side displacement w(r0) and axial force is shown in equation (5): dF(z) dz. As shown in equations (4) and (5), F(z) is the axial force of the pile section at depth z; Ep is the elastic modulus of the pile.
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