Abstract:Research purposes: For the excavation of large underground cavern,it is necessary to determine the proper excavating scheme according to the section shape and geological conditions. Also it is necessary to work out the selection criteria for the scheme according to the actual construction situation for selecting the best scheme. In this paper, the introduction is given to the issues of the stability of the surrounding rock in construction of one large sectional underground cavern,the productions of the minimum damaged floor and the minimum maximum displace caused disturbance during excavation are taken as the the optimal principle,and the simulation calculations of the excavation sequences in the same section with two numerical methods are made for getting the optimal construction scheme.
Research conclusions:(1)For excavation of large underground cavern,the minimum plastic damaged area, the vault settlement and the convergence deformation of the side wall caused by excavation can be used as the criteria for judging the excavation scheme.(2)From the angle of reducing disturbance on the surrounding rock,the excavation scheme of cutting the exposure time of the final boundary of the cavern section,such as first excavation of the pilot tunnel and then excavation of whole section,is better than the excavation scheme of directly excavating the sectional profile.(3)For this project,the excavation scheme of excavation of multiple pilot tunnels is better than the traditional excavation scheme of excavation in layer. ( 4 ) This research result is available for the optimal selection of excavation scheme for excavation of section of the cavern.
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