Analysis Method And Engineering Application Of Reasonable Spacing Of Underground Caverns Based On Strength Reduction And Catastrophe Theory

With the rapid growth of China’s economy,underground caverns in energy,transportation,hydropower and other engineering fields in China are gradually developing towards the deep underground.Due to the interaction between underground caverns,the smaller the spacing between caverns,the more obvious the interaction between caverns,and the more serious the impact on the stability of surrounding rock in underground caverns.Therefore,reasonable determination of the spacing between caverns has very important theoretical significance and engineering application value for ensuring the safety of underground engineering construction and operation,as well as saving engineering construction costs.Based on Hoek Brown’s Strength reduction and catastrophe theory,this paper proposes an analysis method for the reasonable spacing of underground caverns,which provides guidance for the engineering design and construction of underground laboratories.The main research conclusions of this article are as follows:(1)Based on Hoek-Brown strength reduction method and catastrophe theory,an energy criterion for the instability of surrounding rock in underground caverns is proposed.An analysis method for the reasonable spacing of underground caverns is proposed,and corresponding calculation programs are developed and verified by engineering cases.(2)Using the developed calculation program,a numerical analysis was conducted on the reasonable spacing of typical large cross-section caverns in Beishan Underground Laboratory,and the stability safety coefficient of surrounding rock during tunnel group construction under different spacing conditions was calculated.Based on the judgment of the inflection point of the curve between the safety coefficient of caverns and the spacing of caverns,the reasonable spacing of typical large cross-section caverns in the underground laboratory was obtained to be 2.0D.(3)The calculation shows that the safety factor of underground laboratory construction under reasonable spacing conditions reaches 2.34,which meets the requirements of structural design specifications,indicating that the overall structure of underground laboratory construction tunnel group is safe and stable.(4)The calculation reveals the variation patterns of displacement and stress in the surrounding rock of underground laboratory construction.After the excavation of the tunnel construction,the deformation of the surrounding rock is manifested as the arch top sinking,the bottom plate lifting,and the horizontal direction converging towards the tunnel.The maximum displacement of 4.1mm is located at the arch top of the tunnel.Stress concentration occurs at the intersection of the main roadway and parking lot,as well as at the arch crown,arch shoulder,and arch foot of the parking lot.Partial tensile stress occurs at the intersection of the main roadway and parking lot,but the tensile stress value is relatively small.The numerical calculation and model experiment are basically consistent in terms of the variation trend and magnitude of the displacement and stress in the surrounding rock,effectively verifying the rationality and reliability of the analysis method proposed in this article and the developed calculation program.(5)Ranking of sensitivity factors for the influence of mechanical parameters of the Hoek Brown criterion on the stability of underground laboratories under reasonable spacing conditions calculated through grey correlation sensitivity analysis:GSI>D>σci>mi.The calculation shows that the geological strength index GSI is the most sensitive,followed by the rock mass disturbance parameter D,and the sensitivity of mi is the smallest.(6)Grey correlation sensitivity analysis indicates that when grading the rock mass quality in the underground laboratory area and determining the rock mass mechanical parameters,it is necessary to attach great importance to the selection of the geological mechanical index GSI,and reasonably select the construction method of the underground laboratory to minimize the disturbance effect of tunnel construction excavation on the surrounding rock.