崩落法开采引起的岩层移动时效性研究

Investigation of the time-dependent strata movement behaviour caused by caving method

崩落法开采的金属矿山往往会伴随着一系列的地质灾害现象。为保证矿区安全生产,开展崩落法开采引起的岩层移动的时效性研究具有重要意义。以程潮铁矿西区下盘为研究对象,通过将地表10多年GPS监测数据的整理分析,并与现场破坏调查结果和工程地质条件相结合,进而探究不同分区下岩层移动的时效行为。研究结果表明:岩层移动的时效行为与其破坏过程有着密切的关系,不同分区下的岩层移动的时效行为是不同的,可分为初始变形、渐进变形、加速变形和残余变形共4个阶段,分别对应着稳定状态、临界状态、失稳状态以及采矿结束后的蠕变状态;初始变形阶段对应着岩体的初始蠕变过程,渐进变形阶段反映了岩体抵抗自身变形的过程,加速变形阶段与深部破坏面的形成和强烈的应力释放有关;崩落碎石在采矿作业停止后失去了流动空间,在岩体变形挤压下会对围岩提供支撑力进而限制了岩层移动的进一步发展;残余变形时间由岩体的蠕变特性和崩落碎石的压密过程所控制,倾倒滑移区因需要经历一个额外的碎石压密过程而导致残余变形时间更长。

A series of geological disasters are observed in metal mines by sublevel caving method.In order to ensure safe production in mining areas,it is of great significance to carry out research on time-dependent strata movement behavior caused by sublevel caving method.The footwall of western area in the Chengchao Iron Mine was taken as the research case and more than 10 years of GPS monitoring data on the surface were collated and analyzed.By combining the monitoring data with in situ failure investigation and engineering geology,the time-dependent behaviour of strata movement under different zones was studied.The research results indicate that the time-dependent behaviour of strata movement is determined by deformation failure process,and its time-dependent behaviours are different in different zones.It can be further characterized by initial deformation,progressive deformation,accelerated deformation and residual deformation stages.The four time-dependent behaviours correspond to stable state,critical state,unstable state and post-mining creep state.The initial deformation stage corresponds to the initial creep process of the rock mass,and the progressive deformation stage reflects the process of resisting deformation.The accelerated deformation stage is related to the formation of through-going failure surface and the strong stress release.There is no space for the caved waste rock mass to flow after the mining activity is stopped,the strata movement is weakened due to the caved waste rock mass is compacted by surrounding rock mass.The residual deformation time is controlled by the creep characteristics of the rock mass and the compaction process of caved waste rock mass.A longer residual deformation time is observed in in the toppling-slipping zone due to an additional compaction process of caved waste rock mass.