Research On The Disturbance Effect Of The Expansion Of The Existing Cavern Group And The Control Technology Of The Intersection Construction Of The Plane And Façade

With the construction and operation of large-scale underground engineering,my country’s underground engineering has shifted from the construction stage to the stage of equal emphasis on construction and maintenance,and urban underground engineering will gradually enter the stage of maintenance,transformation and expansion.The early underground civil air defense projects were large in volume,long in age,old lining,and environmentally sensitive.They had high requirements for the construction and support of cavern expansion.At the same time,they faced the mutual influence of existing intersecting caverns,surrounding rock expansion disturbance,limited operating space,There are many problems such as large face conversion.Relying on the Guiyang civil air defense project,this paper uses a combination of theoretical analysis,numerical simulation,indoor testing and on-site monitoring to study the construction mechanics theory,surrounding rock disturbance effects and construction control technology of the flat-elevated intersecting cavern.The main research results are as follows:(1)Use the equivalent circle method to map the elliptical cavern into a circle,and explain the general mechanics principle of the construction of a single cavern,and use the complex variable function and the Schwarz alternating method to solve the analytical solution of the displacement and stress of the surrounding rock of the cross cavern.Matlab software is used to realize the algorithm,which provides a theoretical reference for further study of the disturbance effect of the expansion of the flat-facade cross cavern.(2)Through the simulation study of the construction method of the vertical cross cavern,the disturbance law of the surrounding rock after the construction method of the pilot tunnel climbing reverse construction and the top picking method is discussed.And on this basis,the whole process of the excavation of the fa?ade crossing cavern was further simulated,and the disturbance effect of the excavation of the new large-section cavern on the existing cavern was analyzed,and the construction process of the cavern excavation was optimized.(3)Use numerical simulation analysis technology to compare and select the lining dismantling plan of the intersection of plane crossing tunnels.According to the stress and displacement of the surrounding rock and the force analysis of the supporting structure,the optimal lining dismantling plan is obtained.(4)Using the load-structure method and combined with numerical simulation technology,design and analyze the change law of the stress and displacement of the "Y"-shaped main arch,and make a comparative analysis with the triangular main arch.Aiming at the production problem of the "Y"-shaped main arch,a small radius elliptical arc method with a broken line equivalent is adopted to achieve the bending of 30 I-beam steel.(5)Carry out the flexural bearing capacity test of the special-shaped steel arch,verify the mechanical properties of the special-shaped steel arch by comparing with the conventional steel arch,and form a "Y"-shaped main arch + oblique cut arch New type of support system.At the same time,in order to solve the connection problem between the main arch and the oblique arch,a spherical and spherical connection device is used to realize the fine adjustment of the end of the arch.(6)According to the research on the lining removal of the intersection of plane crossing and the structural characteristics of the new steel arch frame,the construction method of "V-shaped groove,frame first,dismantling and supporting" is adopted to realize the intersection of plane crossing.Integrated construction of lining removal + support.And through on-site monitoring,verify the support effect of the new support system and the stability of its own structure.