Research on replacement depth of black cotton soil based on cracking behavior of embankment

基于路堤开裂行为的黑棉土置换深度研究

In order to analyze the influence of replacement depth of black cotton soil(BCS)foundation on the initial cracking depth of a highway embankment,the laboratory tests were performed to construct the constitutive relationship between state variables and stress variables of BCS,and the coupled consolidation theory for unsaturated soils was employed to simulate the change in the major principal stress of the subgrade soils caused by water loss shrinkage of BCS with the help of Abaqus 6.11 codes.The simulation results indicate that the water losing shrinkage of BCS causes tensile stress within the subgrade,which leads to embankment cracking.The crack depth decreases with the increase in the BCS replacement depth and the embankment height,and increases with the increase in the burial depth of BCS.In the distribution area of deep BCS,the key values of foundation replacement depth for controlling the crack depth of the embankment with the height of 1 to 4 m are 1.2 and 1.5 m.In the low filling section,when the buried depth of BCS is 2,3 and 4 m,the key values of the foundation replacement depth to control the crack depth of the embankment are 0.8 and 1.2 m.In order to control the embankment cracking induced by the water losing shrinkage of BCS,a reasonable replacement depth of the foundation should be selected while slope protection is carried out well.

为了分析黑棉土地基置换深度对公路路堤初始开裂深度的影响,通过室内试验,建立了黑棉土的状态变量与应力变量之间的本构关系,然后利用非饱和土固结耦合理论,借助Abaqus 6.11软件模拟了黑棉土失水收缩引起的路基土最大主应力的变化.模拟结果表明:黑棉土失水收缩使路基内部出现拉应力,进而导致路堤开裂,裂缝深度随着黑棉土置换深度和路堤高度的增加而减小,随着黑棉土埋深的增加而增大.在深厚黑棉土分布区,控制高度为1~4 m路堤开裂深度的地基置换深度关键值为1.2和1.5 m.在低填路段,当黑棉土埋深为2、3和4 m时,控制路堤开裂深度的地基置换深度关键值为0.8和1.2 m.为控制黑棉土失水收缩诱发的路堤开裂,在做好坡面防护的同时应选择合理的地基置换深度.