Study On Mechanical Behavior And Surface Subsidence Due To Construction Of Mutate Large-Section Tunnel

When the subway tunnel is in the soft water-rich strata conditions, the engineering construction conditions of mutant cross-section tunnel, the surface building legislating and the underground pipeline network clouding, the construction will be very complicated. Regarding the theoretical research has just begun at hame and abroad. Lagging theoretical study and vigorous development of such projects does not match the reality. Papers based on practical engineering of the 6th line Guangzhou subway donghu station and the stop line, have done more systematic study and discussion to construction technology of mutant large section subway tunnel, mainly about the completion of the job:First of all, the construction plan is designed and selected for the construction of single-mutant large section subway tunnel. The results show that: the size of cross-section should determine construction method of the mutate large-section tunnel; Excavation is more favorable if cross-section is constructed from small to large.Second, the construction plan is designed and selected for the construction of the two-mutate large section subway tunnel. The resule show that: if two-lane dig at the same time, digging right line mutate large-section tunnel is more favorable after the left-line small section tunnel excavated 15m.Third, through elastic-plastic numerical analysis on mutate large-section subway tunnel, we understood displacement and stress changing in the process of the mutation of large section subway tunnel excavation and rock bolting, and obtained construction method and a number of mechanical parameters which provide a basis and guidance for the design and construction.Fourth, when the subway tunnels of small cross-section excavated in the method of using step-by-sted, and the tunnels of large cross-section excavated in the method of CRD, and second engineer officers and small catheter studio ahead of pre-grouting reinforced strata, it can ensure that the construction of mutant large section subway tunnel proceed smoothly and the surface subsidence is controlled effectively.Fifth, through monitoring analysis of the construction and similar model test, we can come to the result that the sinking of surface subsidence and vault is at the control of the volume, rock pressure and support force followed the change law: "rapidly changing-slowly change-basic stability" during the project construction. These prove that the supporting strength and stiffness used in the project are reasonsble and effective, and the program and measures of the construction are feasible.