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Study on the Mechanical Properties of Sandstone and Stability of
Under-river Tunnels under Creep-permeability Coupling
（1. State Key Laboratory of Tunnelling Engineering(SYSU), School of Civil Engineering, Sun Yat-sen University, Zhuhai 519082；2. School of Civil and Architectural Engineering, East China University of Technology, Nanchang 330000; 3. School of Aeronautics and Astronautics, Sun Yat-sen University, Shenzhen 518107; 4.Guangdong Provincial Key Laboratory of Ocean Civil Engineering,Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai 519082）
Abstract To explore the impact of creep effects in sandstone on the long-term deformation behavior of tunnel struc?
tures, this study combines indoor single-stage creep-permeability tests with FLAC 3D numerical simulations. The mechanical properties of sandstone and the stress-deformation patterns of the under-river tunnel under creep-permeability coupling were investigated. The main conclusions are as follows: (1) Single-stage loading creep tests indicate that an increase in axial pressure promotes creep deformation in sandstone, while an increase in confining pressure effectively suppresses deformation. When the seepage pressure exceeds 5 MPa, sandstone maintains a high creep rate, leading to a significant increase in axial deformation. The sensitivity factors affecting the deformation of surrounding rock are ordered as follows: seepage pressure > axial pressure > confining pressure; (2) The multi-field coupling tunnel model established using FLAC 3D accurately simulates the creep and permeability characteristics of sandstone strata in tunnels, with tunnel deformation and stress stabilizing after the eighth year of operation; (3) As the burial depth of the tunnel increases, the phenomena of tunnel crown settlement, waist convergence, and invert arch heaving become more pronounced, with maximum deformation occurring at the crown. The sensitivity of tunnel deformation is ordered as follows: crown > invert arch > waist; (4) An increase in the groundwater level significantly
affects vertical settlement and horizontal convergence of the tunnel, with the most notable increase in seepage pressure occurring in the invert arch area. Special attention should be given to changes in hydraulic pressure in this region.
Abstract：
To explore the impact of creep effects in sandstone on the long-term deformation behavior of tunnel struc?
tures, this study combines indoor single-stage creep-permeability tests with FLAC 3D numerical simulations. The mechanical properties of sandstone and the stress-deformation patterns of the under-river tunnel under creep-permeability coupling were investigated. The main conclusions are as follows: (1) Single-stage loading creep tests indicate that an increase in axial pressure promotes creep deformation in sandstone, while an increase in confining pressure effectively suppresses deformation. When the seepage pressure exceeds 5 MPa, sandstone maintains a high creep rate, leading to a significant increase in axial deformation. The sensitivity factors affecting the deformation of surrounding rock are ordered as follows: seepage pressure > axial pressure > confining pressure; (2) The multi-field coupling tunnel model established using FLAC 3D accurately simulates the creep and permeability characteristics of sandstone strata in tunnels, with tunnel deformation and stress stabilizing after the eighth year of operation; (3) As the burial depth of the tunnel increases, the phenomena of tunnel crown settlement, waist convergence, and invert arch heaving become more pronounced, with maximum deformation occurring at the crown. The sensitivity of tunnel deformation is ordered as follows: crown > invert arch > waist; (4) An increase in the groundwater level significantly
affects vertical settlement and horizontal convergence of the tunnel, with the most notable increase in seepage pressure occurring in the invert arch area. Special attention should be given to changes in hydraulic pressure in this region.
MA Jianjun1,
4 TANG Rong1 LIU Cong2 HUANG Weizhen1 LIN Yuexiang3
.Study on the Mechanical Properties of Sandstone and Stability of
Under-river Tunnels under Creep-permeability Coupling[J] MODERN TUNNELLING TECHNOLOGY, 2024,V61(5): 156-166
2024, Vol. 61 