钟祥市磷矿区复合型地面塌陷形成机制研究

Study on Formation Mechanism of Composite Ground Collapse in Phosphate Mine Area of Zhongxiang City

钟祥市磷矿区地面塌陷是岩溶和采矿共同作用下的复合型地面塌陷,其影响因素众多、形成过程复杂,给地面塌陷监测预警和综合防治工作带来了诸多挑战。为查明复合型地面塌陷的形成机制,以钟祥市磷矿区地面塌陷为研究对象,选用FLAC3D数值模拟软件对塌陷区岩层的应力应变特征进行模拟计算,并结合地面塌陷分布规律进行综合分析。研究结果表明,复合型地面塌陷的形成与矿区的岩溶地质条件、采空区以及地下水等关系密切。岩溶地质条件为塌陷形成提供了物质基础,地下水为塌陷形成提供了动力条件,采空区则是塌陷形成的首要诱发因素。三种因素相互作用、相互影响,导致区内地面塌陷大规模发生。依据区内地面塌陷影响因素和变形破坏模式,复合型地面塌陷的形成演化大致可划分为四个阶段①磷矿开采前,溶洞潜伏稳定阶段;②磷矿初采时,采动裂隙控制土洞形成阶段;③局部矿柱破坏时,岩层移动破坏加速土洞发展阶段;④顶板整体冒落时,地表位移引发土洞失稳形成塌陷阶段。

Surface collapses of phosphate mines in Zhongxiang city are composite surface collapses under the action of karst and mining,which bring many challenges to the monitoring,warning and comprehensive prevention of surface collapses,because of their many influencing factors and complicated forming process.In order to find out the formation mechanism of composite surface collapses,the paper takes the surface collapses of phosphate mines in Zhongxiang city as the research object and selects the FLAC3D numerical simulation software to simulate the stress-strain characteristics of strata in the subsidence area,and analyzes the distribution law of surface collapses.The results show that the formation of surface collapses are closely related to the karst geological conditions,goaf and groundwater in the mining area.The karst geological conditions provide the material basis for the collapses,the groundwater provides the dynamic conditions for the collapses,and the goaf is the primary inducing factor for the collapses.The factors interact with each other and influence each other,which caused a massive collapse of the ground in the area.According to the influence factors and deformation failure modes of ground collapse in the area,the formation and evolution of complex ground collapse can be roughly divided into four stages:①Before phosphate mining,the karst caves are at the stage of latent stability;②At the beginning of phosphate mining,mining-induced fracture controls the formation of soil cavity;③When local pillars are broken,the movement and destruction of rock strata accelerate the development of soil cavity;④When the roof of gob falls as a whole,the displacement of the ground surface causes the instability of the soil cavity to form collapses.