Structural Mechanical Response And Waterproof Performance Of Shield Tunnel Under The Influence Of Fault Dislocation

As a special geological structure,fault fracture zone poses great challenges to the design and construction of underground structures because of its risk of faulting.Nowadays,with the large-scale application of shield construction technology in China,whether shield tunnel can effectively cope with the risks brought by violent geological activities during design life has become a key issue for relevant researchers to consider.Therefore,it is necessary to carry out relevant research on the mechanical response of shield tunnel under fault dislocation.Based on the project of Jinan rail transit Line 4crossing Qianfoshan fault zone,this paper explores the influence of fault displacement on the stress,deformation and waterproofing of shield tunnel by means of indoor model test and numerical simulation.The main research work and achievements of this paper are as follows:(1)The self-designed model test box is used to carry out loading tests on tunnel structure models under different fault forms.The experimental results show that the influence of faults on the structure is mainly concentrated in the range of 60 m near the fault projection surface;Normal fault and reverse fault have different influences on the stress characteristics and failure modes of tunnel structures;The whole structure under normal fault is in the state of longitudinal eccentric tension,while the structure under reverse fault is in the state of eccentric compression;The shear failure effect of normal fault is greater than that of reverse fault.(2)A three-dimensional calculation model of shield tunnel across fault is established to carry out a fine analysis on the related problems of shield tunnel affected by faults.The research results show that lateral deformation of the structure is controlled by the contact pressure between the arch bottom and soil.Under the same dislocation distance,the circumferential joint of shield under normal fault is mainly tensile deformation,showing tensile failure,while the circumferential joint under reverse fault is mainly shear deformation,showing shear failure.(3)The validity analysis of elastic grouting ring and setting flexible joint is carried out by using three-dimensional calculation model of shield tunnel across fault.The results show that both methods can effectively reduce the influence of fault dislocation on tunnel structure,and the protective effect is mainly reflected in the longitudinal direction.For the circumferential stress and deformation,the protection measures have no obvious improvement effect,and the protection effect of the two measures on the arch bottom is better than the tunnel vault.(4)Based on the material aging formula,the load-bearing capacity of tunnel is studied.The results show that the load-bearing capacity of longitudinal bolts decreases by 13%,the anti-breaking performance decreases by 32%,and the anti-breaking performance of segment structure decreases by 23.5% due to the material aging.Therefore,more attention should be paid to anti-aging measures of bolts in design and construction.(5)Mooney-Rivlin model is used to evaluate the waterproof performance of deformed waterproof gasket.The results show that: rubber contact surface is the weakest link in waterproofing of segment joints,T-type joint waterproof ability is weaker than linear joint,T-type joint waterproof weak position is at the junction of the circumferential joint and the longitudinal joint.In order to ensure that the tunnel doesn’t occur water leakage phenomenon in design service life,we should ensure that the circumferential joint opening is not more than 6mm,the longitudinal joint opening is not more than 4mm.