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Relying on the tunnel engineering crossing large active fault fracture zone in high intensity seismic area in Western China, a large-scale model test of tunnel through multiple slip surfaces under strike slip motion was carried out. The deformation patterns and damage characteristics of tunnel structure and surrounding rock were studied based on displacement, strain and internal force response, as well as crack morphology. The results revealed that microscopically the model soil experienced the process of contacting, compaction and relative movement under fault dislocation, and was macroscopically accompanied with fracture occurring, and further expansion. Compared with fault movement form containing single slip surface, the active wall produced nonlinear linkage displacement to fault fracture zone when there existed multiple slip surfaces. The model soil exhibited a multistage dislocation along longitudinal direction after test. The dislocation of model soil on both sides of major slip surfaces reached to 25.9 mm and 18.8 mm, which was about 2.2-3.4 times of the dislocation on both sides of the minor slip surfaces in fault fracture zone. The overall deflection of lining segments and the torsion of flexible joints corporately undertook the fault dislocation. Lining segments near the major slip surfaces had opposite trends of tensile and compressive deformation, where the failure of tensile bending damage was dominant. Tunnel segments near minor slip surfaces underwent integral linear deflection along with surrounding rock, and were less affected by fault dislocation. The fragile sections of tunnel structure were located near main slip surfaces, the fragile parts were invert, arch springing and arch spandrel, which were mainly damaged by tensile, compressive and shear affection. Based on the deflection corner beta of each lining segment, combined with damage pattern and internal force distribution trend, it is suggested that 2d similar to 3d (d represents the span of tunnel) in range near major slip surfaces is the main affected zone, while the range of 4d in the middle of fault fracture zone is the minor affected zone. The partitioned fortification needs to be adopted when tunnel is to cross fault fracture zone.

期刊论文 2024-04-01 DOI: 10.1016/j.soildyn.2024.108541 ISSN: 0267-7261

To study the potential disasters caused by tunnels crossing water-abundant fault areas, this study takes the Jinyunshan Tunnel as an example, and studies the groundwater flow law between different rock layers, the interaction between surrounding rock hydrostatic pressure and soil pressure, and the mechanical features and safety of the lining during construction by combining field tests and finite element simulation analysis. The results show that the displacement change rate of the tunnel vault reaches 2.8 mm/d, and the maximum earth pressure and hydrostatic pressure are 2.3 MPa and 1.15 MPa, respectively, both at the bottom of the tunnel in II. When the tunnel enters the fault fracture zone from the V surrounding rock, the bending moment of the lining increases by 222.78% at the left haunch and 60.87% at the bottom of the right wall. The axial force of the right spandrel increases by 2579.2%, and the left spandrel increases by 221.18%. The safety factor of the two sections is greater than 2.4, indicating that the overall structure is in a safe state, but the safety factor of the second right shoulder is 2.54, which is close to the safety threshold of 2.4. The research results provide a basis for the safety design and construction safety of tunnels through water-rich sections in similar fault fracture zones, and provide a reference for reducing groundwater loss and protecting ecological vegetation.

期刊论文 2024-02-01 DOI: 10.3390/buildings14020475

Grouting is a widely used approach to reinforce broken surrounding rock mass during the construction of underground tunnels in fault fracture zones, and its reinforcement effectiveness is highly affected by geostress. In this study, a numerical manifold method (NMM) based simulator has been developed to examine the impact of geostress conditions on grouting reinforcement during tunnel excavation. To develop this simulator, a detection technique for identifying slurry migration channels and an improved fluid -solid coupling (F -S) framework, which considers the influence of fracture properties and geostress states, is developed and incorporated into a zero -thickness cohesive element (ZE) based NMM (Co-NMM) for simulating tunnel excavation. Additionally, to simulate coagulation of injected slurry, a bonding repair algorithm is further proposed based on the ZE model. To verify the accuracy of the proposed simulator, a series of simulations about slurry migration in single fractures and fracture networks are numerically reproduced, and the results align well with analytical and laboratory test results. Furthermore, these numerical results show that neglecting the influence of geostress condition can lead to a serious overestimation of slurry migration range and reinforcement effectiveness. After validations, a series of simulations about tunnel grouting reinforcement and tunnel excavation in fault fracture zones with varying fracture densities under different geostress conditions are conducted. Based on these simulations, the influence of geostress conditions and the optimization of grouting schemes are discussed. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY -NC -ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

期刊论文 2024-01-01 DOI: 10.1016/j.jrmge.2023.04.011 ISSN: 1674-7755
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