Analysis Of Ground Settlement Induced By Water Bursting In Shallow Coal Seam

Mine flooding is one of the five major disasters that often occur during coal mining,which seriously restricts the rapid development of mining economy.Mine flooding not only directly affects the smooth progress of coal mining activities,but also causes secondary disasters such as coal-rock column instability,secondary water inrush,and ground settlement.Among them,the ground settlement caused by mine floods has seriously affected the production and life of the mine residents and the local ecosystem.It is the key step to reduce the ground settlement and evaluate the stability of existing ground facilities to deeply analyze the law of groundwater level change and the stress characteristics of soil particles after mine floods from the perspective of mechanics.(1)Based on the classification of existing mine water bursting,this paper summarizes the type of mine water bursting which caused ground settlement:surface water and loose layer pore water as the water inrush source,and mine water bursting which caused the water level of phreatic aquifer to decrease will lead to ground settlement;Due to the different properties of the overlying strata,there are certain differences in the specific forms of ground settlement.(2)The soil density varies with the change of water content.When analyzing the change of soil effective stress caused by the decrease of water level in phreatic aquifer,the change of soil density from saturated gravity to natural water content is considered and the calculation method of effective stress change of soil mass considering the change of soil weight in stratified soil state is deduced.The hypothetical water column isolation model is introduced to analyze the seepage force applied to the soil particles during the flow of water between the soil particles.When the water head difference is large,the seepage force generated by the water flow process will also lead to the consolidation and compression of the soil.(3)Based on the characteristics of overlying strata in different mines,according to the Dupuit differential equation,the calculation method of groundwater level drop after mine flooding under different overlying strata conditions is obtained.Combined with the consolidation compression theory,the calculation method of ground settlement induced by mine flood considering the change of soil density and seepage force is obtained.(4)Based on the mine flood from the phreatic aquifer in Meng yao Village,Xiao County,combined with the specific stratum parameters,this paper analyzed the change of the water level of the phreatic aquifer after the mine flood,considered the change of the effective stress of the soil and the ground settlement in the area of the change of the water level under different factors,compared and analyzed the theoretical analysis with the measured data to verify the correctness of the theoretical analysis.Based on the analysis of the ground settlement,the stability of existing structures in the mining area is evaluated,and the effective measures to reduce the ground settlement induced by mine floods are put forward.The research results have important theoretical and practical guiding significance.