岩溶区地连墙底部溶洞稳定性分析方法

Stability analysis method of Karst caves at the bottom of ground connecting walls in Karst areas

为了解决岩溶区地连墙灌注阶段与溶洞间岩层稳定性问题,首先,依据岩溶区地连墙灌注阶段受浆液荷载作用的岩层力学特性,将上部覆盖岩土层等效为重度相同的岩层,建立岩层等效计算模型;然后,将地连墙底部及侧部的分布荷载视为作用于岩层内部,利用Mindlin解分别求出两种荷载作用下半无限空间内应力计算式;再基于复变函数进行岩层自重作用下溶洞边界的地层应力解析;最后,将墙底部与侧部的浆液荷载作用下产生的地层应力与岩层自重作用在含有溶洞地层的应力叠加,由此得到地连墙底部荷载与侧部荷载作用在含有溶洞的地层应力,在此基础上通过应力变换求得溶洞边界上的最大主应力和最小主应力,并引进Griffith强度准则,进行溶洞稳定性评判。结果表明:地层应力计算得出受上述荷载作用下溶洞边界处的应力最集中,因此在工程应用中,可通过对溶洞边界上岩层失稳关键点进行验算进而判断溶洞在地连墙浆液荷载作用下是否会破坏;理论计算结果与工程实际能够较好吻合,为岩溶区地连墙注浆液荷载作用下岩溶空洞稳定性评判提供了一种新的、更接近工程实际的理论分析方法。

In order to solve the problem of the stability of the rock formation between the ground wall and the Karst cave in Karst area during grouting stage,firstly,according to the mechanical properties of rock layer subjected to slurry load in the grouting stage of the ground wall in Karst area,the upper covering rock and soil layer is equivalent to the rock layer with the same weight,and the equivalent calculation model of rock formation is established.Secondly,the distributed loads at the bottom and side of the ground connection wall are regarded as acting on the inside of the rock stratum,and the calculation formulas of the internal stress in the semi-infinite space under the action of the two kinds of loads are obtained by Mindlin solution.Thirdly,based on the complex variable function,the formation stress analysis of the boundary of Karst cave under the action of the self-weight of the rock formation is carried out.Finally,the stratum stress generated by the grout load at the bottom and side of the wall and the stress acting on the stratum containing the Karst cave by the self-weight of the rock layer are superimposed,and the bottom load of the ground connection wall and the side load acting on the stratum containing Karst cave are obtained.On this basis,the maximum principal stress and the minimum principal stress at the boundary of the Karst cave are obtained through stress transformation,and the Griffith strength criterion is introduced to evaluate the stability of the Karst cave.The results show that:according to the calculation of the formation stress,the stress at the boundary of the Karst cave is the most concentrated under the above loads.Therefore,in engineering applications,the key points of rock instability at the boundary of the Karst cave can be checked to determine whether the Karst cave will be destroyed under the action of grout load of the ground connection wall.The theoretical calculation results are in good agreement with the actual engineering practice,which provides a new theoretical analysis method that is closer to the engineering practice for evaluating the stability of Karst cave under the load of ground connecting wall grouting in Karst area.