The Development Law And Treatment Technology Of Ground Fissures Due To Underground Mining In Loess Hilly Area Of Western China

As the coal resource in eastern mining areas exhausting and coal westwardstrategy becoming reality, ground fissure disaster caused by underground miningarouses people’s concern increasingly. Mining areas in western China havecharacteristic of shallow buried, simple strata, thick loose bed, landform undulatesterribly and so on. Because of the double stress effects of geological miningenvironment and topography condition, the development laws of ground fissures aremore complicated.Aiming at the Ground fissure disaster caused by underground mining in loesshilly areas of western China, on the basis of field measurement, supplemented by soilmechanics experiments, rock mechanics experiments and numerical simulation, basedon theories of mining subsidence, strata damage and slope sliding, the classificationmethod of ground fissures due to underground mining was put forward, thedevelopment law was revealed, the formation mechanism was researched, all types ofground fissure prediction models were set up, and the comprehensive treatmenttechnical measures were proposed. The main results are as follows:(1) Taking the typical loess hilly area Shendong mining area as research base, onthe basis of engineering drilling, soil mechanics experiment and rock mechanicsexperiment, the physical and mechanical properties of loose bed and overburden rockwere researched. Three comprehensive monitoring networks of surface movement andground fissure development were established above the working faces of12208,22201, and52304of Daliuta coal mine. Laws of surface movement and groundfissure development of three different depth coal seams1-2,2-2,5-2were researchedrespectively.(2) On the basis of field investigation and observation, the ground fissuredisasters caused by underground mining were classified. According to the developingperiods, ground fissures could be classified into the temporary fissure during theprocess of mining and the permanent fissure after surface subsidence was steady.According to the formation mechanisms, ground fissures were divided into four types,such as stretching fissure, compressing fissure, collapsing fissure and sliding fissure.(3) Combined with theories of mining subsidence, overlying rock destruction,and slope sliding, the formation mechanisms of all types of ground fissure due tounderground mining were researched, and the prediction models were established. Stretching fissure was formed due to the surface horizontal deformation exceeding themaximum tensile strain of topsoil, which developed in the surface tensile area of themining boundary. Compressing fissure was formed because of the topsoil’s upliftcaused by compression deformation, which developed in the dynamic compressionarea of surface with mining. Collapsing fissure was formed because of the breaking ofthe whole overburden rocks and surface, which developed just above the working facewith the dynamic breaking of the basic roof. Sliding fissure was formed because ofthe combined influence of mining and slope sliding, which developed only whenmining under valleys.(4) Aiming at the sliding fissure developed when mining under valleys, usingnumerical simulation method of UDEC software, dynamic and static ground fissuredevelopment laws of different valley angles and different relative positions betweenvalley and working face were researched.(5) The influencing factors of ground fissures due to underground mining in loesshilly areas were analyzed. The relationships among ground fissures and mining speed,the ratio of strata thickness and mining thickness, surface deformation, topographyand geomorphology were researched. After that the experience prediction modelswere established.(6) Aiming at the temporary fissure in the process of mining and the permanentfissure after surface subsidence steadying, different treatment technologies of groundfissures were researched, and the―three-step‖method of deep filling, shallow soiling,and vegetation construction was put forward. Ground fissure filling system of superhigh water material was developed. Taking the ecological construction demonstrationproject in the coal base of the contiguous area of Shanxi-Shaanxi-inner Mongolia asthe experiment base, ground fissure filling treatment engineering test was put forward,which provided technical support to teatment of ground fissures in loess hilly areas ofwestern China.