岩溶区下伏溶洞加筋土地基承载破坏特性分析

Analysis of bearing failure characteristics of reinforced soil foundation in karst area

为探讨溶洞对加筋地基的影响,利用有限元建立数值模型,对比分析有无加筋下溶洞地基土体变形、土拱效应及筋材受力变形规律,探讨溶洞地基的破坏特性,结果表明:地基的破坏模式与溶洞埋深H、溶洞宽度b的比值及是否加筋有关,无筋地基在H/b≤2时为冲切破坏,在H/b=3时为整体剪切破坏;加筋地基在H/b=1时为冲切破坏,在H/b≥2时为整体剪切破坏。当H/b≥2时,溶洞地基会产生土拱效应,除土拱效应外,加筋地基土工格栅处还出现次拱效应。地基的极限承载力随着溶洞深度的增加而增大,无筋地基中,H/b=2与H/b=3的极限承载力较H/b=1增大1.022、1.293倍,加筋地基中,H/b=2与H/b=3的极限承载力较H/b=1增大1.169、1.267倍。

In order to explore the influence of karst on reinforced foundation,the numerical model was established by using finite element method.The failure characteristics of karst cave foundation are discussed by comparing and analyzing soil deformation,soil arch effect and stress deformation law of geosynthetics.The results show that the failure mode of foundation is related to the ratio of the buried depth of cave to the width of cave and whether it is reinforced or not.The failure mode of unreinforced foundation is punching failure when H/b≤2,and the failure mode is general shear failure when H/b=3.The failure mode of reinforced foundation is general shear failure at H/b≥2,and the failure mode is punching failure at H/b=1.When H/b≥2,the soil arching effect will be generated.In addition to the soil arching effect,the secondary arching effect may occur at the geogrid of the reinforced foundation.The ultimate bearing capacity of the foundation increases with the depth of the cavern.In the unreinforced foundation,the ultimate bearing capacity of H/b=2 and H/b=3 is increased by 1.022 and 1.293 times compared with H/b=1.In the reinforced foundation,the ultimate bearing capacity of H/b=2 and H/b=3 is 1.169 and 1.267 times higher than H/b=1.