考虑三维空间效应的砌块土坡侧向土压力分析

3D effects on lateral earth pressure in block-faced soil slopes

在支挡结构稳定性设计中,基于侧向土压力系数的设计方法简单易用,一直被广泛用于实际工程中。已有侧向土压力系数主要在平面应变分析方法下计算获得,忽略了三维空间效应的影响。基于三维边坡稳定分析方法,采用变分法获得安全系数极值下对应的三维破坏机制,建立考虑三维效应的砌块土坡侧向土压力计算方法,从而揭示三维效应对砌块土坡侧向土压力大小的影响规律。提出的方法还考虑了砌块与土摩擦作用力和水平地震力的影响。给定参数值,通过优化计算获得了不同长高比下的三维砌块土坡水平土压力系数,以图的形式给出便于使用。从计算结果可以发现,在地震作用下,三维空间效应对侧向土压力的影响显著,特别是对于垂直的支挡结构。最后结合算例,通过与传统的平面应变下侧向土压力结果进行对比分析,显示了考虑三维效应的土压力系数对支挡结构稳定性设计的重要性。

The design of retaining structures oiien relies on the lateral earth pressure coefficient, and this method is widely used in practical engineering problems. The traditional approaches for calculating the lateral earth pressure coefficient are performed under plane-strain condition by ignoring the end effects posed by three-dimensional （3D） characteristics. Based on a 3D slope stability analysis, the variational limit equilibrium analysis is used to obtain the minimum factor of safety and its corresponding critical 3D failure mechanism. The object of this study is to propose a procedure for calculating the lateral earth pressure in block-faced soil slopes considering 3D effects and to investigate the 3D effects on the lateral earth pressure. The soil-facing interface friction and horizontal seismic forces are also considered. The results are presented in the form of charts that give the lateral earth pressure coefficients from an extensive parametric study in which various ratios of length to height are used. An optimization procedure is employed. It is found that the impact of seismicity is significant, especially for the vertical retaining structures. An example is also given to demonstrate the difference in the lateral earth pressures obtained from the classic earth pressure equation and 3D analyses, showing the importance of 3D effects on lateral earth pressure coefficient in retaining structures.