Research Of Surface Deformation Induced By Pipe-Roof Group Driven In Close Proximity

In soft ground, non-digging method for tunnel excavation has a certain effect on surrounding environment. Taken in-site geological and hydrological condition of the area of tunnel cross section in accounted, a suitable method play a supporting role of for the safety and stability of rock and soil surrounding the tunnel excavation cross section before excavation. Pipe-roof pre-construction method is one of the constructional technology created to give support before subsurface tunnel excavation. Hence, it it inevitable for the ground to deform by driven pipe-roof group. Compared with traditional pipe-roof method using small diameter pipes, pipes with larger diameter are utilized in the pipe-roof pre-construction method resulting in huger subsidence.Pipe jacking is one of the most essential part in this method, safe jacking construction has effective reduction on the risk of huge underground space’s digging. Based on detail analysis and results for mechanics of pipe-roof made by researchers at home and aboard, models are built by a finite element software midas/gts in comparison with in-site investigation data for model parameters’verification giving reference value to similar construction projects.In this paper, some essential missions are completed as following:(1) Looking up references about pipe-roof and pipe-jacking, mechanics of pipe-roof with construction procedure and deformation induced by pipe-jacking are illustrated;(2) Making use of distances in pipe-roof cited by the soil arch effect theory in piles, the distance between adjacent pipes in design is verified for stability and safety;(3) Analyzing the investigations occurred by driven pipe-roof group in detail. Based on geology and hydrology of a subsurface tunnel project in Zhuhai in Guangdong province,2-D finite element models of large diameter jacking pipes construction in oral shape arrangement with close proximity are built up by midas/gts to analyze the surface deformation as well as ground lateral displacement. In order to verified the rationality of the monitoring data and numerical results, Theoretical calculations for pipe-roof group are analyzed without interaction with each pipe in condition of subsidence calculation induced by a single pipe jacking;(4) Although simulation results of stress analysis and seepage-stress coupling analysis concerning soil lateral displacements indicate that pore pressure has no effect on lateral displacement, Underground water flush occurred by pipe jacking still has an outstanding and harmful effect on surrounding environment except for ground loss. Unsteady flow coupling analysis is used to simulate surface subsidence with the decline of underground water level. Tezaghi consolidation theory is utilized for comparison and verification among calculation, simulation results and investigations.