岩溶区土洞塌陷演化过程研究--以龙岩市樟坑自然村土洞塌陷为例

Soil Cave Collapse Process in Karst Area--A Case Study of Soil Cave Collapse in Zhangkeng Natural Village,Longyan

以福建省龙岩市樟坑自然村发生的岩溶区土洞塌陷为研究对象,通过室内物理模型试验及数值模拟分析,对岩溶区土洞塌陷过程中覆盖层土体的应力、应变(位移)、塑性区分布规律等进行研究,从而再现土洞塌陷演化过程,总结土洞塌陷演化规律。结果表明,在土洞孕育、形成及扩展过程中,土体中始终存在土拱效应,其发挥程度受初始洞径及覆盖层厚度影响,土洞塌陷过程其实是土拱效应产生及失效过程。土体中最大剪应力主要集中于拱脚位置,而塑性区分布则以拱顶为主,土体竖向变形也以拱顶为中心向四周递减。塌陷后土洞呈中心大、两头小的纺锤状,其最大洞径与初始洞径及覆盖层厚度呈线性正比例关系。同时,根据塌落土体累计质量的增量大小可将土洞塌陷演化过程简化为三个阶段:土洞发育形成、内部塌陷扩展以及地表塌陷阶段。

By taking the soil cave collapse occurred in the Zhangkeng Natural Village,Longyan City,Fujian Province as an example,the stress,strain(displacement)and plastic zone distribution of overburden soil during the collapse process of karst soil cave were analyzed through indoor physical model test and numerical simulation analysis.The evolution process of an earth cave collapse was simulated and summarized based on the evolution law of earth cave collapse.The results show that in the process of gestation,formation and expansion of soil caves,the soil arching effect always exists in the soil,and its degree of exertion is affected by the initial hole diameter and the thickness of the overburden.The collapse process of soil caves is actually the generation and failure process of soil arch effect.The maximum shear stress in the soil mainly concentrates at the arch foot,while the plastic zone is mainly distributed at the arch top,and the vertical deformation of the soil decreases from the arch center to the surrounding area.After the collapse,the hole shape is a spindle with great center and small ends,and the maximum hole diameter is linearly proportional to the initial hole diameter and overburden thickness.At the same time,according to the incremental mass of the collapsed soil,the collapse process of soil cave can be simplified into three stages:the formation of soil caves,the expansion of internal collapse and the collapse of the surface.