狭窄基坑平动模式刚性挡墙被动土压力分析  

Study of passive earth pressures against translating rigid retaining walls in narrow excavations

作　　者：应宏伟[1,2] 郑贝贝[1,2] 谢新宇[1,2] 

机构地区：[1]浙江大学岩土工程研究所,杭州310058 [2]浙江大学软弱土与环境土工教育部重点实验室,杭州310058

出　　处：《岩土力学》2011年第12期3755-3762,共8页Rock and Soil Mechanics

基　　金："十一五"国家科技支撑项目(No.2008BAJ06B00)

摘　　要：对于地铁车站、地下管道沟槽等狭窄基坑,其被动区土体宽度有限,不满足半无限体的假定,采用经典的库仑、朗肯土压力理论计算挡墙被动土压力是不合适的。首先建立了无黏性土中狭窄基坑刚性挡墙的有限元分析模型,研究了挡墙相对平移时不同宽度土体的被动滑裂面的分布规律;借鉴库仑平面土楔假定,建立了狭窄基坑刚性平动挡墙被动土压力的理论计算模型,推导了被动极限状态下滑裂面倾角及被动土压力系数的解析公式;再采用水平薄层单元法,得到了被动土压力分布、土压力合力作用点高度的理论公式。结合算例,深入研究了这种工程背景下挡墙被动滑裂面倾角的影响因素,以及被动土压力合力、土压力分布及合力作用点位置与经典库仑土压力理论的差别,与数值计算结果的对比验证了该理论方法的合理性。研究发现,当被动区土体宽度小于满足半无限体的临界值、且墙土摩擦角大于0时,被动滑裂面倾角大于传统库仑被动滑裂面倾角,被动土压力大于经典库仑解,合力作用点高度则小于库仑解,且基坑越窄,墙土摩擦角越大,其差别越大。For the case of narrow excavations such as subway stations and underground pipe,the width of the soil mass in passive zone is limited,so it＇s unsuitable to use the classical Coulomb or Rankine earth pressure theory to calculate the passive earth pressure.A finite element numerical model for retaining wall in narrow excavations is presented.The slip surfaces in the soils at passive limiting state with different widths of soils when the walls translating are investigated.Based on the concept of Coulomb sliding soil wedge,a new theoretical model for determining passive earth pressures against translating rigid retaining walls in narrow excavations is proposed.The formulae of the inclination angles of slip surfaces and coefficients of the resultant passive pressures are obtained.Then the horizontal differential element method is introduced and the unit passive pressures and the points of application of the resultant earth pressures are proposed.The factors that influence the inclination angle of slip surface under this circumstance are studied in detail.The comparisons between theoretical and numerical values show that the proposed equations satisfactorily predict the earth pressure on the wall.It is also shown that if the width of soil mass in passive zone is less than a critical value and the wall friction can not be negligible,the inclination angles of slip surface and the passive earth pressures are larger;while the heights of points of application of pressures are less than Coulomb＇s solution.The narrower the pit or the rougher the wall-soil interaction is,the more significant the differences are.

关 键 词：狭窄基坑 平动模式 挡土墙 滑裂面倾角 被动土压力 

分 类 号：TU432[建筑科学—岩土工程]