Abstract To research the failure mode of the shallow hard-rock tunnel by the action of overload, the study on a large similar model test is conducted on the basis of QY-7+177 monitoring section of The Affiliated Hospital of Qingdao University West Coast District Station of Qingdao Metro Line 6. Unit weight, compressive strength, tensile strength and angle of internal friction are used as the main control parameters of the material to truly reproduce and simulate the physical and mechanical properties of cross-sectional rock mass, and the non-contact strain measurement system is used to observe the process of fissure evolution. A series of inverted V-shaped shear fissures with an included angle of 25°~40° with the crown normal appears during the process of overload, and combined with the Griffith theory of brittle strength, the maximum principal initiation stress of the fissure that first appeared directly above the vault is calculated to be 0.409 MPa, which is 21.6% of the uniaxial compressive strength of similar materials.Test results show that fissures begin to appear on the crown of the surrounding rock of the tunnel even if the stress is relatively low, indicating that it is a hazardous area prone to fissure initiation of the surrounding rock. The failure mode of the surrounding rock of the tunnel is the shear-extrusion failure mode: the arch is subject to shear failure and the rock mass is broken and extruded at the foot of the arch to damage phase coupling.
Abstract：
To research the failure mode of the shallow hard-rock tunnel by the action of overload, the study on a large similar model test is conducted on the basis of QY-7+177 monitoring section of The Affiliated Hospital of Qingdao University West Coast District Station of Qingdao Metro Line 6. Unit weight, compressive strength, tensile strength and angle of internal friction are used as the main control parameters of the material to truly reproduce and simulate the physical and mechanical properties of cross-sectional rock mass, and the non-contact strain measurement system is used to observe the process of fissure evolution. A series of inverted V-shaped shear fissures with an included angle of 25°~40° with the crown normal appears during the process of overload, and combined with the Griffith theory of brittle strength, the maximum principal initiation stress of the fissure that first appeared directly above the vault is calculated to be 0.409 MPa, which is 21.6% of the uniaxial compressive strength of similar materials.Test results show that fissures begin to appear on the crown of the surrounding rock of the tunnel even if the stress is relatively low, indicating that it is a hazardous area prone to fissure initiation of the surrounding rock. The failure mode of the surrounding rock of the tunnel is the shear-extrusion failure mode: the arch is subject to shear failure and the rock mass is broken and extruded at the foot of the arch to damage phase coupling.
LIU Quanwei1,
2 LIN Wenhao1 LI Weiteng1 QIN Zhe1 FENG Qiang1 YANG Xuxu1
.Study on Model Test of Shallow Hard-rock Tunnel Failure Mode by the Action of Overload[J] MODERN TUNNELLING TECHNOLOGY, 2022,V59(6): 125-131
2022, Vol. 59 