A Irregular Hexahedral Mesh Discretization Method For Wall Rock Of Salt Caverns With Multiple Feature Constraints

With the development of society,human’s demand for energy is increasing.The exploitation and storage of energy is very important for national development.So much energy is consumed in China,and a problem is how to store energy after energy exploitation.Salt rock has very low permeability and good creep behavior,which can ensure the sealing of salt cavity.Its mechanical properties are relatively stable,and it has the ability of self-recovery from damage.Therefore,it is recognized as an ideal place for energy storage.However,the premise of salt rock for energy storage must ensure its stability.Moreover,salt rock has the characteristics of small salt thickness,multiple mudstone interlayers and shallow burial depth in China.Therefore,it is of great significance to study the stability of salt rock by studying the grid model of salt cavern surrounding rock with multi-feature constraints under real geological conditions.Combined with the existing three-dimensional geological model of salt cavern surrounding rock,it is relatively simple to consider multi-feature constraints such as real salt cavern and strata,and most of them are irregular tetrahedral rock mass meta-models,while irregular hexahedral body element models have better geometric features and precision expression than tetrahedral ones.In view of the real and complex geological conditions,a method for discretization of irregular hexahedral meshes in salt cavern surrounding rock with multiple feature constraints is proposed.The main research work is as follows:(1)Construction of three-dimensional surface model of salt cavern surrounding rock with multi-feature constraintsA three-dimensional surface model of salt cavern was constructed based on sonar detection data as the hole constraint of the three-dimensional geological model of salt cavern surrounding rock.A three-dimensional formation model was constructed based on borehole data,boundary data and formation data as the face constraint,and a three-dimensional surface model of salt cavern surrounding rock with multiple feature constraints was constructed by combining the hole constraint,surface constraint and boundary data.(2)Construction of irregular tetrahedral volume element model of salt cavern surrounding rock with multi-feature constraintsAiming at the intersection of salt cavern three-dimensional surface model and ground plane in complex geological environment,a method based on constraint bounding box is proposed to deal with the intersection problem of salt cavern and ground plane.Then,a multifeature constraint irregular tetrahedral body element model of salt cavern surrounding rock is constructed based on Tet Gen tetrahedral mesh division program.(3)Construction of irregular hexahedron volume element model of salt cavern surrounding rock with multi-feature constraintsOn the basis of constructing the irregular tetrahedron body element model of salt cavern surrounding rock with multi-feature constraints,the indirect method is used to convert tetrahedron into hexahedron,that is,one tetrahedron into four hexahedron according to the idea of "midpoint decomposition method",and the algorithm of tetrahedron to hexahedron template is designed to realize the conversion of tetrahedron body element model into irregular hexahedron body element model.In this paper,a salt cavern in Changzhou,Jiangsu Province was taken as the experimental object,and the irregular hexahedral volume element model of surrounding rock of salt cavern with multi-feature constraints was constructed through case analysis.The quality of the model was evaluated and the influencing factors were analyzed,and the models constructed with different maximum volume constraint parameters were compared and analyzed to obtain the optimal model construction parameters,and the effectiveness of the proposed method was verified.