| With the increasing demand of rock salt as industrial raw material,the problems of geological hazards and environmental safety,such as excessive subsidence,collapse,salinization of land,are becoming more and more prominent.This is mainly caused by the goaf cavity formed by the water-soluble mining of rock salt deposits,then at home and abroad,more and more researches have been made on the stability of cavern overlying rock after water-soluble mining of salt ore.Based on the project of Ningjin Salt Mine in Hebei Province,this paper has analyzed the regional engineering geology and hydrogeological conditions,then the stability and surface deformation of overlying rocks in Ningjin mining area were studied deeply by means of theoretical calculation and finite difference numerical simulation,and the quantitative simulation and prediction of surface deformation under different working conditions were also carried out.The main research work and results are as follows:(1)This paper collected and analyzed some related data,such as the regional topography,geomorphology,geological structure,stratigraphic lithology and its distribution in Ningjin salt mining area,as well as the engineering geology,hydrogeology and mining status of salt mining area,etc.,then we have had a better understanding of the regional geological background of the mining area.For one thing,the detailed strata and structural distribution,groundwater types,aquifer and aquiclude characteristics,engineering geological rock groups and environmental geology were basically found out in the study area.For another thing,the physical and mechanical parameters of related rock and soil mass were also obtained by sampling,collecting and laboratory testing all kinds of drilled rock and soil mass in the study area.(2)Based on the research results at home and abroad,the influencing factors of deformation stability of overlying rock in water-soluble mining were analyzed.Combined with the geological environment and the actual mining method of Ningjin Salt Mine,critical depth,critical horizontal stress around the overlying rock,maximum settlement at the center of the earth's surface and influence range of the earth's surface were calculated by critical non-collapse theory,elastic circular plate theory,layered transfer theory and probability integral theory under the condition of single cavity limit solution expansion mining.(3)The simplified model of numerical simulation were established by using FLAC3 D finite difference numerical simulation software.And the basic law of surface deformation were obtained through the simulation of single cavity expansion under different working conditions,then we analyzed the the influence of diffusion radius and internal pressure on surface deformation.At the same time,the surface deformation of water solution mining in Ningjin mining area were quantitatively simulated and predicted under the condition of single cavity limit expansion.(4)The numerical model is verified according to the data recorded by the combined well subsidence observation system,the numerical model is found to be reliable at the same time,the surface deformation calculated by the three-dimensional integral formula of surface deformation is coMpared with the numerical modulus,the results agree well with each other.Based on the results of theoretical calculation and numerical simulation,the suggested values of surface deformation prediction are given.This paper provides a scientific basis for the mining and prevention of surface deformation and subsidence of Ningjin Salt Mine.Moreover,the research method and simulation in this paper have certain reference value for similar water solution mining research. |
PDF Full Text Request