岩溶土洞演化及其数值模拟分析

贾龙; 蒙彦; 管振德

岩溶土洞演化及其数值模拟分析

中国地质科学院岩溶地质研究所/国土资料部、广西壮族自治区岩溶动力学重点实验室；中国地质科学院岩溶塌陷防治重点实验室

基金项目: 国家自然科学基金项目（41302255）；国家自然科学基金项目（41302288）

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出版历程
- 发布日期: 2014-09-25

Evolution and numerical simulation of a karst soil cave

Institute of Karst Geology, CAGS/Key Laboratory of Karst Dynamics,MLR & GZAR；Key Laboratory of Karst Collapse Prevention, CAGS

摘要

摘要: 土洞是覆盖型岩溶区一种隐伏的不良地质现象。土洞在水的作用下发育演化最终形成塌陷，可通过地下水位的变化来研究土洞发育和塌陷的形成。同时土洞的演化会造成覆盖土体不均匀位移和应力重分布，可通过覆盖土体位移和应力变化来进行研究土洞演化过程。采用FLAC3D三维有限差分程序，分析覆盖层垂向位移场表明：最大垂向位移出现在土洞顶部，使拱顶出现拉张破坏，并可根据洞顶土层位移的数值模拟结果，划分“等沉面”确定土洞扰动的土层深度。分析覆盖层剪切应力场表明：在土洞拱趾部位出现剪应力集中，会造成拱趾的剪切破坏，并可根据洞顶“剪应力低值区”，判断覆盖层中土拱效应的存在。分析覆盖层塑性区表明：较为坚硬的黏土层中，土洞以拱顶塌落和拉张破坏为主，最终可以形成坑壁较为陡直的桶状或坛状塌坑。土层较为松散时，以拱趾的剪切破坏为主，最终可以形成锥碟形塌陷坑。利用“剪应力低值区”，“等沉面”和“塑性区”可综合判断土洞的稳定性以及覆盖层所能形成的极限土洞大小。岩溶土洞演化规律及数值模拟研究对岩溶塌陷（土洞）早期监测和评价有着重要的理论及工程意义。
- 岩溶塌陷 /
- 土洞 /
- FLAC3D /
- 数值模拟
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 displacement 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 collapse resulted from shear failure of the arch toe. The low shear stress area, equal settlement plane and plastic 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 engineering results for monitoring and evaluation of early stage karst collapse.
- karat collapse /
- soil cave /
- FLAC3D /
- numerical simulation

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