Stability Analysis Of Underground Water-sealed Caverns

Underground water seal caverns have the advantages of high safety performance and good economic benefits,which become the preferred storage method for petroleum and liquefied gas at home and abroad.However,the development of underground water-sealed caverns is short in my country,and some core construction technologies have not yet been fully mastered.Therefore,the research on underground water-sealed caverns needs to be further strengthened.In this paper,relying on "a underground water-sealed propane cavern project in Qingdao",the stability of its surrounding rock is analyzed.On the basis of considering factors such as meteorological and hydrology,topography,geomorphology,stratum lithology,geological structure,in-situ stress,rock physical and mechanical parameters,storage medium and other factors,combined with the "Q method system" classification evaluation method to establish a numerical calculation model.Taking the displacement,stress,plastic zone,etc.in the numerical simulation results as evaluation indicators,comparative analysis of the axial direction of the cavern,the buried depth of the cavern,the cross-sectional shape of the cavern and the distance between the caverns under different working conditions were carried out to determine the optimal cave.The direction of the chamber axis is NW350°,the optimal buried depth and elevation is-125 m,the stability of the elliptical cavern is better than that of the straight wall and round arch cavern,and the optimal cavern distance is 42m(2.1 times the span).Through the analysis of the overall stability of the cavern group after excavation and the stability of the shaft under the above layout scheme,the results show that after the excavation of the main cavern,the cavern group is in a stable state and there is no large area of damage.However,the displacement value of the side walls at the end of the main cavern 3 and 4(within the range of 300?370m)is 11.7?15.7mm,which requires strengthening of support and monitoring;the compressive stress at the top of the cavern is relatively large,ranging from 10MPa?17MPa.In the case of step-by-step excavation,the overall stability of the shaft is good,but a large area of plastic zone appears in the top 20 m depth of the rock mass after excavation,and support needs to be strengthened;The stress value is 23.3MPa,and attention should be paid to the safety of this part during construction.