Abstract By using the block discrete element numerical simulation method and creating the boundary conditions of bolt shearing, the numerical simulation study on the sectional distribution characteristics and evolution law of shear of tunnel systematic bolts has been conducted, and how the factors such as surrounding rock fracture degree and bolts layout pattern will affect the bolt shear has been investigated. The study results are stated as follows: (1) The shear of the tunnel systematic bolts and joint shear displacement are in positive correlation, and the shearing effect of bolt happens in broken rock mass and is negligible in intact rock mass; (2) The bolt shear is always less than the axial force at the same position, but the maximum shear-axial force ratio is close to 75%; (3) In the initial stage of bolt installation, the bolt shear will differ considerably due to the installation position and the distance between bolt and inner contour surface of tunnel, and the bolt shear peak in the initial stage of installation may be higher than the long-term stable value; (4) Greater broken rock volume or greater breaking range in the broken rock mass means greater bolt shear; (5) Longer bolts are more susceptible to shear, and densely placed bolts can help reduce the shear sustained by the systematic bolts.
Abstract：
By using the block discrete element numerical simulation method and creating the boundary conditions of bolt shearing, the numerical simulation study on the sectional distribution characteristics and evolution law of shear of tunnel systematic bolts has been conducted, and how the factors such as surrounding rock fracture degree and bolts layout pattern will affect the bolt shear has been investigated. The study results are stated as follows: (1) The shear of the tunnel systematic bolts and joint shear displacement are in positive correlation, and the shearing effect of bolt happens in broken rock mass and is negligible in intact rock mass; (2) The bolt shear is always less than the axial force at the same position, but the maximum shear-axial force ratio is close to 75%; (3) In the initial stage of bolt installation, the bolt shear will differ considerably due to the installation position and the distance between bolt and inner contour surface of tunnel, and the bolt shear peak in the initial stage of installation may be higher than the long-term stable value; (4) Greater broken rock volume or greater breaking range in the broken rock mass means greater bolt shear; (5) Longer bolts are more susceptible to shear, and densely placed bolts can help reduce the shear sustained by the systematic bolts.
ZHAO Dongping1,
2 ZHANG Bohao2 LI Hua3 ZHAO Xiaoyu3
.Discrete Element Numerical Simulation Study on Shear Characteristics of Tunnel Systematic Bolts Based on Shear Boundary[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(3): 112-122
2023, Vol. 60 