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