Stability Analysis Of Surrounding Rock Of Underground Water-sealed Rock Cavern Oil Depot Under The Influence Of Fault Fracture Zone

With the advantages of high security,small investment,small occupation,large reserves and short construction period,underground water-sealed rock cavern oil storage has gradually become the preferred oil storage method in many countries.At present,most of the oil storage depots built in China are underground water-sealed rock cavern oil storage.The underground water-sealed rock cavern oil depot has the characteristics of large span,long axial direction,high side wall,no or little support,and the geological structure of the reservoir area is generally more complex,which inevitably falls within the influence range of fault fracture zone.Therefore,it is of great significance to study the stability of surrounding rock under the influence of fault fracture zone.In this paper,numerical simulation method is adopted,and FLAC3 D finite difference software is used to simulate and analyze underground water-sealed cave oil depot,and the influence of fault fracture zone on the stability of surrounding rock of cavern group is studied,which provides reference for future engineering practice.The main research contents and conclusions of this paper are as follows:1.The FLAC3 D finite difference software is used to establish the same numerical simulation model as the existing experiments,and the correctness of the selected constitutive model and modeling method is verified by comparing with the fracture surface and ultimate load in the test results.2.Based on three discriminant indexes,i.e.,displacement around surrounding caves,total volume of plastic zone and safety factor of surrounding rocks,the rational spacing of caverns,excavation sequence and excavation layers of main caverns are optimized and analyzed.The results show that the rational spacing between caverns is 1.8 times the average span of adjacent caverns.The reasonable excavation sequence of cavern group is synchronous excavation of each main cavern;The reasonable number of layers excavated in the cave room is four.3.The numerical simulation model of fault fracture zone is established by using parameter weakening method.The synchronous excavation of each cavern and the excavation of four floors in the cavern are selected.Based on three discriminant indexes,i.e.displacement around the surrounding cave,total volume of plastic zone and safety factor of surrounding rock,the influence of dip angle,thickness of fault fracture zone and distance from excavation contour plane of cavern on the stability of surrounding rock is analyzed.The results show that:It has the greatest influence on the side wall and vault of the main cavern near the fault fracture zone;When the dip angle is 60,the stability of surrounding rock is the worst;Thickness change has little influence on the stability of surrounding rock.When the distance is more than 1 times the span of the main cavern,the influence on the stability of surrounding rock is small.4.Orthogonal test is designed to study the deformation sensitivity of weak parts under the influence of fault fracture zone.Taking the dip angle,thickness of fault fracture zone and distance from the excavation contour plane of cavern as factors,and taking the displacement of monitoring points on the side wall and vault of main cavern adjacent to the fault fracture zone as evaluation indexes,the range analysis of test results is carried out.The results show that:The most sensitive factor of vault deformation is distance,and the most sensitive factor of left side wall deformation is inclination angle.