斜坡地基桩前土抗力的应变楔模型修正

Modification of strain wedge model for soil resistance in front of piles in sloping ground

针对斜坡地基桥梁基桩承载特性,引入斜坡地基水平极限承载力模型及平地应变楔模型,提出适用于斜坡地基桩前土抗力计算分析的桩前土楔模型,包括上部土楔及下部修正应变楔2部分。根据不同的土体强度发挥程度,提出桩前土楔的3个发展阶段。讨论下部修正应变楔与平地地基应变楔的区别,并基于静力平衡方程,推导上部土楔提供的土抗力随深度变化的计算公式。研究结果表明:桩前土楔模型地基土抗力计算结果与模型试验及工程实例的数值模拟结果均较吻合,可用于合理预测斜坡地基桩前土抗力;当桩顶水平荷载增大时,应变楔深度增大,应变楔层数也不断增加;内摩擦角发挥值不断增大,近似呈非线性增大,增大速度逐渐变慢。

Considering the behavior of piles in sloping ground, a soil wedge model was proposed to evaluate the soil resistance in front of piles in sloping ground by developing the strain wedge technique in level ground and employing the model for lateral ultimate bearing capacity in sloping ground. The soil wedge model consisted of two parts, i. e. upper soil wedge and lower modified strain wedge. Three development stages of the soil wedge on the basis of the exerting extent of the soil strength were proposed. The calculation formula for soil resistance along with depth in the upper soil wedge was derived based on the equilibrium equation,while the difference between the lower modified strain wedge technique and the strain wedge technique in level ground was discussed. The results show that the calculation results obtained by the proposed model are well consonant with the model test results and the numerical results for an engineering project. It is reasonable to predict the soil resistance in front of piles in sloping ground by the suggested model. The depth and layers of strain wedge increase with the increase of the lateral loads atop the pile, the fan angle nonlinearly increases, and the growth rate slows down gradually.