负压作用下土洞型岩溶塌陷机理及力学模型研究

Mechanism of soil-cave type karst collapse under negative pressure and its mechanical model

岩溶矿区快速抽排岩溶水会造成真空负压吸蚀效应,诱发岩溶地面塌陷,破坏地表生态环境。为了研究该类型岩溶地面塌陷机理,依托武汉市江夏区乌龙泉矿区岩溶地面塌陷实例,开展了具有可视化剖面的物理模型试验,探索负压作用下覆盖层内土洞几何形貌演化过程。通过建立三铰拱结构力学模型,研究了负压吸蚀力、土拱厚跨比、强度参数对土拱破坏模式和稳定性的影响机制。研究表明:负压作用下土洞型岩溶地面塌陷经历“无扰动-分层差异沉降-土拱承载-地面塌陷”4个演化阶段,地表沉降具有突跳特征,层内越靠近岩溶开口沉降越大;随着土拱厚跨比增加,土拱更趋近于整体滑移破坏,而不易产生弯折破坏;负压增大或土体强度参数弱化,都将降低土拱稳定性。

The rapid drainage of karst water in mining areas may cause the vacuum negative pressure suction effect,which induces overburden-collapse and destroys the surface ecological environment.In this paper,relying on an example of karst collapse in Wulongquan mining area in Jiangxia District,Wuhan City,a physical model test with a visual profile was carried out to explore the evolution process of the geometric morphology of the soil cave in the overburden under negative pressure,and a three-hinged arch structure mechanical model was established.Based on the presented mechanical model,the influence of negative pressure,soil arch thickness-span ratio and strength parameters on soil arch failure mode and stability were researched.The research results showed that the soil-cavern collapse under negative pressure experienced four evolution stages,namely undisturbed,layered differential settlement,soil arch bearing,ground collapse.The surface subsidence had the characteristic of sudden jump.The closer the layer was to the karst opening,the greater the settlement was.With increase of the arch thickness-span ratio,the soil arch was closer to the overall sliding failure,not a bending failure.The increase of the negative pressure or the weakening of the soil strength parameters will all reduce the stability of the soil arch.