挡土墙与土界面摩擦角为负的地震被动土压力解析解

Analytical solution of seismic passive earth pressure for negative friction angle of wall-soil interface

目前大多数被动土压力问题研究的是挡土墙背与土界面摩擦角为正的情况(墙身相对土体向下移动),而挡土墙与土界面摩擦角为负(墙身相对土体向上移动)的被动土压力问题则研究的较少。在平面滑裂面假设的基础上,利用散粒体Ktter方程得到破裂面土抗力的分布,结合拟静力法通过极限平衡分析得到了挡土墙与土界面摩擦角为负时的地震被动土压力系数、被动土压力合力和被动土压力合力作用点高度的理论公式。在地震荷载作用下,竖向地震加速度系数总是减小被动土压力,水平向地震加速度系数或减小或增加被动土压力系数取决于挡土墙倾角、挡土墙背与填土界面摩擦角、填土摩擦角。随地震加速度系数的增加,地震被动土压力系数变化越明显。利用破坏土楔弯矩平衡条件得到了地震被动土压力的作用点高度,且土压力作用点高度随水平向地震加速度系数的增加而减小。地震被动土压力系数和土压力作用点高度与相关文献结果吻合较好,可为锚、输电线路等基础受上拔荷载时设计所采用。

Most of the existing analyses of passive earth pressures behind retaining walls deal with the case of positive wall-soil interface friction angles（the wall moves downwards relative to the backfill）,while the researches on passive earth pressures for the negative wall-soil interface friction angle case（the wall moves upwards relative to the backfill） are still lacking.Based on the planar rupture surfaces hypothesis,a theoretical formula for the seismic passive earth pressure coefficient,the resultant force of earth pressure and the application point of the resultant is obtained by using the Ktter equation and the combination of pseudo-static approach with the limit equilibrium method of analysis for the negative wall-soil interface friction angle case.The seismic passive earth pressure coefficients always decrease with the increase of the vertical seismic acceleration,but the horizontal seismic acceleration results in either an increase or a decrease in the earth pressure coefficients,depending on the combinations of the wall batter angles,wall-soil interface friction angles and soil friction angles.The variation of seismic passive pressure coefficients increases with the increase of the magnitude of the earthquake acceleration.The proposed analysis lies in its ability to compute the point of application of the passive thrust,for which moment equilibrium condition of failure wedge is effectively utilized.The application point of the passive thrust decreases with the increasing values of horizontal seismic acceleration coefficients.The computed values of the seismic passive pressure coefficients and the point of application of passive thrust agree with the available results,which can be served for anchor and transmission line foundations under uplift loading.