Research On Activation Pattern Of Water Filled Old Mining Area And Prediction Of Surface Movement Deformation

When construction is carried out on the surface above the old mining area,the activation of the old mining area may cause further ground settlement and deformation,threatening the safety of buildings,and it is crucial to ensure the safety and stability of the construction site in the old mining area.To this end,this paper uses a combination of model tests and theoretical analysis to investigate the overburden and surface movement deformation problems caused by water-filled activation of old mining areas.The main work of this thesis is as follows:(1)Based on the geological mining conditions and similarity theorem of the old mining hollow area underneath the construction site of Jianye Guangmingfu in Pingdingshan,a similar model of the old mining hollow area is made to analyze the overburden rock destruction characteristics of the old mining hollow area by the long-arm collapse method.(2)The compaction and deformation characteristics of collapsed and broken rocks in old mining hollow areas under different environments(dry,water-filled and graded immersion)were investigated using a home-made compaction device with similar material crushed specimens of collapsed zone rocks(mudstone and sandstone)as the research object.(3)A prediction model applicable to the ground movement deformation above the water-filled old mining hollow was constructed based on the probabilistic integral method and applied to the movement deformation prediction of the construction site of Jianye Guangmingfu in Pingdingshan.The main research results are as follows:(1)The collapse zone is divided into the boundary hollow zone and the intermediate pressure-dense zone according to the overburden damage characteristics of the old mining hollow zone by the long-arm collapse method.The friction coefficient of the broken rock body in the middle of the old mining hollow area decreases after filling with water,and is re-deformed under the action of overburden pressure,manifesting as long-term slow creep deformation,while the broken rock moves toward the boundary hollow area,leading to the rapid filling of the boundary hollow in the old mining hollow area and inducing deformation of the overburden rock layer.The residual cavities and voids in the broken rocks of the collapse zone are the main"activation"space in the water-filled old mining hollow.(2)There is a relationship of"water-filled>dry"for the compression(z),creep stage compression(Δz)and creep stage void rate change(Δp)of broken specimens of similar materials in water-filled and dry states,and a relationship of"water-filled<dry"for the residual void rate(p).For the old mining area,the water level has not yet filled the entire mining area,the collapse zone broken rock has already produced a large deformation,subsequent water filling on the collapse broken rock weakened the impact of the deformation produced less than 30%of the entire creep stage deformation.When predicting the surface movement deformation caused by the"activation"of the water-filled old mining area,the nature of the water-filled fractured rock is used for evaluation to ensure the safety of the site construction.(3)The prediction results of the ground movement deformation in the study area of Jianye Guangmingfu in Pingdingshan show that the ground movement deformation caused by the water-filled"activation"of the collapse zone is the most intense near the cavernous area at the boundary of the old mining area,and the predicted residual settlement value of the ground surface in the study area is 17.13mm,the tilt value is0.39mm/m,the curvature value is 0.02mm/m~2,horizontal movement of 7.38mm,tensile deformation of 0.21mm/m and compressive deformation of 0.39mm/m.