非极限状态主动土压力与填土张拉裂缝研究

为了进一步完善非极限状态主动土压力计算中的不足,并就填土张拉裂缝深度的理论计算展开研究,以复杂工况下刚性挡土墙为研究对象,综合考虑挡土墙变位模式、填土种类、墙背与填土面倾角、墙土摩擦、填土张拉裂缝影响及超载作用等因素,基于薄层单元法,并结合墙土相互作用强度参数与位移的非线性关系,推导得到一种非极限状态主动土压力计算公式;通过与文献特例、试验数据比对,验证了所构建公式的合理性。当墙背填土为黏性土时,利用土压力计算公式及挡土墙模型中的几何关系,建立了填土张拉裂缝深度与挡土墙位移的关系方程,并绘制出不同影响因素下裂缝深度随挡土墙位移的变化曲线,其变化规律与模型试验结果基本吻合。研究结果表明:考虑因素的增多使得非极限状态主动土压力计算过程变得复杂,但假设条件与实际工况更加接近,其计算误差得以降低,且通过迭代法计算方程可以得到满意的数值解;张拉裂缝开展深度随挡土墙位移呈非线性增长,在位移初期增长较快,而接近极限位移时裂缝开展趋于稳定;不同因素对于填土张拉裂缝开展产生的作用存在差异,其中填土内摩擦角和黏聚力影响显著,超载和填土面倾角影响次之,墙背倾角影响最小;降低填土抗剪强度,增加超载以及选择仰斜式挡土墙均有助于抑制张拉裂缝的开展。

Active Earth Pressure and Tensile Crack of the Fill in a Non-limit State

To improve the accuracy of the active earth pressure calculation formula in a non-limit state further, and study the theoretical calculation of a tension crack depth of fill, the rigid retaining wall under complex working conditions was the focus of the research. Factors such as the displacement mode of the retaining wall, the type of fill, the inclination angle of wall back and fill surface, the friction between the wall and fill, the influence of the fill tension crack, and the overload effect, were considered to derive a formula for calculating the active earth pressure in a non-limit state. This was based on the thin-layer element method and the non-linear relationship between strength parameters and the displacement of the wall-soil interaction. The rationality of the formula was verified through comparisons with special cases in the literature and experimental data. With clay as the fill, the relationship equation of the depth of the fill tension crack and the displacement of the retaining wall was formulated by using the earth pressure formula and the geometric relationship in the retaining wall model. Further, the variation curves of the crack depth with the displacement of the retaining wall due to different factors were plotted. The variation rules are fundamentally consistent with the model test results. The results show that the calculation process of the active earth pressure in a non-limit state becomes complex as the factors increase. However, calculation errors are reduced because the assumed conditions are similar to actual working conditions. Thus, satisfactory numerical solutions of the calculation equation can be obtained by the iterative method. The development of a tension crack depth increases nonlinearly with the displacement of the retaining wall and increases rapidly at the initial stage of the displacement, while it tends to be stable near ultimate displacement. Different factors have different effects on the development of a fill tension crack. Therefore, the internal friction angle and cohesion of the fills have significant effects. The overload and inclination angle have less significant effects, while the inclination angle of the wall back has the least significant effect. Reducing the shear strength of the fill, increasing the overload, and choosing inclined retaining walls restrains the development of a tension crack.