Research On Stress And Deformation Properties Of Jet Pile Composite Foundation In Deep Buried And Large Section Loess Tunnel

After loess tunnel was excavated, carrying capacity of natural basement is often difficult to meet the design requirements, the tunnel after the completion tend to produce larger basal deformation, therefore, in order to construction process and post-operational safety of the tunnel, must be carried out the foundation reinforcement. In this paper, based on Fu Jiayao 1# tunnel as the research object, using the jet grouting pile reinforcement treatment on the basement of the loess tunnel. In order to analyze the stress and deformation law of the pile and soil between the piles in tunnel base, analysed and studied by field test and finite element, mainly analyzes the stress and deformation characteristics of untreated and using the jet grouting pile treatment on the basement of the loess tunnel under deep buried conditions. Combined with the results of the analysis, evaluated stability of tunnel after the jet grouting pile treatment. This paper main research contents are as follows:1.According to the field test results of Fu Jiayao 1# tunnel, analyzes the temporal variation laws of pile top and soil between piles stress, the pressure of wall and basal surrounding rock, and basic trend of the tunnel basement subsidence deformation in flat large section three-lane loess tunnel basement under deep buried condition.2.Using the finite element software MIDAS/GTS, based on Fu jiayao 1# tunnel project, conducted two-dimensional numerical simulation respectively on the tunnel construction process tunnel of untreated and using the jet grouting pile treatment on the basement of the loess tunnel. Analyze distribution of pile stress, axial force of pile shaft, pile-soil stress of the tunnel basement along the depth of the pile; trends of vertical displacement and lateral displacement during tunnel excavation, and the distribution of plastic zone around the tunnel.3.According to the results of field tests and numerical simulation, analysis accumulated maximum of field testing basement deformation, and accumulated maximum value of basement deformation, vault subsidence and peripheral convergence about the numerical results, the safety factor of lining and plastic zone range, and analysis settlement caused by the inverted arch backfill and supporting structural deadweight after the tunnel construction is completed by numerical simulation, comparing the measured and simulated results with standard value, evaluation stability of the loess tunnel after basement jet pile reinforcement.Through the study of jet grouting pile to deal with the loess tunnel basement, aims to provide a reference for similar tunnel engineering design and safety construction.