Evolution and numerical simulation of a karst soil cave

JIA Long; MENG Yan; GUAN Zhen-de

Abstract：Soil caves in karst areasarea concealed and adverse geological phenomena.The evolution of a soil cave can cause uneven displacement and stress redistribution on the overlying soil layer,conversely changes in displacement and stress can be used to study soil cave evolution using three-dimensional finite-difference software FLAC3D.The vertical displacement field of the soil layer shows that,the maximum vertical dis-placement taking place on the arch roof of the soil cave may cause tensile failure of the arch roof.Based on the level of soil layer displacement on the arch roof,an"equal settlement plane" can be drawn to determine the depth of the soil cave.The shear stress field of the soil layer indicates that,the maximum shear stress in the arch toes can cause arch toe shear failure,and the "low shear stress area" can be used to determine the impact of the arching effect on the overlying soil layer.Through analysis of the plastic zone of the soil layer, it is concluded that,in rigid clay areas,soil caves with barrel bottle-shaped pit collapse were mainly caused by arch roof collapse and tensile failure;while in areas of loose soil,caves with taper or plate-shaped pit col-lapse resulted from shear failure of the arch toe.The low shear stress area,equal settlement plane and plas-tic zone can be adopted to evaluate the stability of soil caves and the limits on hole size in the overlying layer. Evolution and numerical simulation of karst soil caves in this study provide important theoretical and engi-neering results for monitoring and evaluation of early stage karst collapse.