Deformation Regularity Of Surrounding Rock In Abandoned Mine For Gas-storage Under Cyclic Inject-product

Abandoned mine gas storage,one of the important ways to reuse waste space resources,plays a role in promoting the transformation and upgrading of resourceexhausted cities,national energy security,economic and social development.During the operation of the underground gas storage,the surrounding rock undergoes damage and deformation under the cyclic injection-production and the gas seepage-stress coupling,posing a threat to the safety of the gas storage.In this paper,the combination of numerical simulation,laboratory test and theoretical analysis is used to study the damage evolution characteristics,seepage-damage-stress coupling mechanical model of rock under cyclic loading and unloading,and the stability mechanism of the surrounding rock of gas storage under cyclic injection and circulation conditions.The research was carried out and the following main research results were obtained:(1)The mechanical properties and failure characteristics of sandstone under different loading conditions are obtained.As the confining pressure increases,the sample shows a tendency to transform from brittle to ductile,and the proportion of the elastic deformation stage before the peak decreases.As the axial strain increases,the velocity of the post-peak stress decreases.Under the condition of true triaxial loading,the tendency of the sample to change from brittle to ductile is more affected by the minimum principal stress.(2)The damage evolution law of sandstone under triaxial compression and cyclic loading and unloading conditions is revealed.Based on the calibration of rock mesomechanical parameters based on various loading conditions,a numerical model of particle flow under conventional triaxial loading,true triaxial loading and cyclic loading and unloading conditions was constructed.The stress and strain of rock under different loading conditions were analyzed.The mechanical properties of sandstone damage evolution are proposed for the characteristics,fracture propagation law and damage evolution characteristics.(3)The seepage-damage-stress coupling mechanical model of surrounding rock in abandoned space under injection-production cycle is established.Based on the Biot porous media model,Darcy's seepage law and damage evolution model reveal the coupling relationship between permeability,porosity,gas pressure,solid deformation and damage variables.(4)The influence of gas storage pressure and sealing layer on the gas tightness and stability of the surrounding rock of the gas storage is elucidated.Under the condition of complete surrounding rock,the gas storage pressure plays a supporting role for the roadway;with the damage evolution of the surrounding rock,the higher gas storage pressure will cause the expansion of the damage range and the increase of the roadway deformation;the sealing layer can effectively alleviate the storage.The influence of gas pressure and injection-production cycle on the damage and deformation of the roadway improves the stability and gas storage efficiency of the gas storage roadway.There are 56 figures,7 tables and 95 references in this thesis.