Study Of Deformation Characteristics Of Broken Rock Came From Caving Zone Of5^th Coal Seam In South Side Of The Zhahe Coal Mining Area

Coal, as a kind of non-renewable and indispensable energy mining has been widely used.Under the premise of the current technology,how to solve the problem about the environmental resources after coal extraction is important.Accurate prediction and evaluation of mining subsidence is very important for improving the utilization of land resource, the remediation of environment and life safety of the residents in the mining area.The paper collected a lot of geological data of Zhu Zhuang mining area in Huaibei which come from the south of Zhahe mining area, by the conditions of tectonic geology and hydrogeology, it analysis the environment of broken rock deformation in the mined-out area caused by five coal seam fully mining.The height of the caving zone is about10m above the five coal seam,the height of the diversion fissure zone is about40.7m above it,the curved zone is up to the earth’s surface;the mined-out area has good ability of water storage and inflow,so the rocks inside can be water saturation.Through the physical simulation of rock compaction and the numerical simulation of FLAC2D,the paper has a qualitative and quantitative analysis of the second broken rock deformation in the mined-out area.Through the analysis of the result from the experiment of broken rock physical compaction,we can know that under the condition of water coupling,the broken rock deformation is a process which has initial rapid expansion and then further compaction.The deformation is affected by the positive pressure above the rock,moisture content in the rock,the lumpiness and the strength of rock.The strength of the deformation is proportional to the positive pressure and the moisture content,bu it will disppear after them achieve a constant value.The lumpiness of rock is the main influencing factor when the moisture content is the same and the positive pressure is small, but go along with the positive pressure increase,the strength of rock will become to the main influencing factor.The paper used the software called FLAC2D to do the numerical simulation for calculating the amount of settlement caused by five coal seam fully mining. The result pointed out that the amount of settlement is175mm when the mined-out area is stable equilibrium as first time.The amount of settlement respectively is200mm and230mm when there are six floors and twelve floors constructions were respectively built in the center of the mined-out area above the surface.After the broken rocks filled in the mined-out area are water saturation,there will be10mm settlement more,called "second subsidence".