A Study On Construction Mechanics And Monitoring System Of Cover And Excavation Up-Down Method

This thesis investigated the simulation technology of the whole construction process of cover and excavation up-down method, analyzed the loading and deformation pattern of subway structures, summed up the main construction technology, by applying the finite differential code FLAC3D, based on the design and construction of Xiashuijing station of Shenzhen Subway Line 5. The work done and major achievements are as follows.●According to the project features, three-dimensional modeling was used to analyze and optimize the different excavation procedure of up-down method. It was achieved that the effect to enclosure structure is little difference when using one-way and two-way opposite excavations. The construction period will be greatly reduced by using two-way opposite excavations.●Applying three-dimensional modeling, analyzed the stress adjustment and the safety of the stress concentrated part of enclosure structure by using of stress path and Mohr-Coulomb criterion. It was achieved that the stress change was happened when the first excavation of each layer. The place of minimum safety is in the connection part of center pillar and middle plate.●Applying three-dimensional modeling contrasted and analyzed the different excavating segmentation of up-down method. It was achieved that these had same influence for different segmentation excavation. In the practical construction, the segmentation distance would be 40-70m, so it can greatly reduce period.●From the project features, a realtime monitoring system was established. By monitoring the unfavorable parts of the underground structure and analysing monitored data, it was found that all the deformation was within the allowable range and no unusual signal was initiated.The achievement above provided an effective guidance to the optimization of design and construction of the Xiashuijing station of Shenzhen Subway Line 5.