对挡墙后无粘性填土中破裂面的研究

Study on active and passive failure surface in backfilled cohesionless soil behind rigid retaining wall

在传统的库伦土压力理论中,刚性挡墙后无粘性填土中的破裂面被假定为平面。然而,一些室内试验和现场测试结果均已证明了实际破裂面是曲面。以刚性挡墙后无粘性填土中的破裂面为研究对象,以竖向微分单元法为基础,利用变分原理推导了主、被动状态下关于破裂面曲线的微分方程,并对该方程进行了求解。研究结果表明,当墙背光滑或墙背与土体的摩擦系数为定值时,填土中的破裂面和破裂角均与库伦土压力理论相同;当墙背与填土的摩擦系数呈线性规律变化时,对应的破裂面为曲面。最后,讨论了墙背摩擦角和填土内摩擦角对破裂角的影响。

In the classical Coulomb's earth pressure theory,the failure surface in the backfilled cohesionless soil behind rigid retaining wall in slope engineering is assumed a plane.However,it has been proved by a number of laboratory and field tests that this failure surface is actually a curved surface.In this paper,based on the vertical differential element method and the variational principle with moveable boundary,a quadratic ordinary differential equation of the first order about the failure surface is deduced. Three cases of the equation are discussed:1)without lateral shear force at the interface between two elements,and the back of the retaining wall is frictionless,the failure surface is a plane;2)lateral shear force is a constant,and the back of the wall is rough,the failure surface is also a plane,the two cases above mentioned are identical to Coulomb's theory;3)lateral shear force increases linearly from the tip to the toe,the failure surface is a curved surface.Results show that the proposed approach can predict right failure pattern of the backfilled cohesionless soil,which is in good agreement with that of the laboratory and field tests.