Stability of a Rock Block in a Tunnel Roof Under Constant Normal Stiffness Conditions

Xiao

Mathematical Problems in Engineering

2020

A numerical analysis method for block failure is proposed that is based on continuum mechanics. First, a mesh model that includes marked blocks was established based on the grid-based block identification method. Then, expressions of the contact force under various contact states were derived based on the explicit contact force algorithm, and a contact simulation method between blocks and the surrounding rock was proposed. The safety factors of the blocks were calculated based on the strength reduction method. This numerical analysis method can simulate both the continuous deformation of the surrounding rock and the discontinuous failure processes of the blocks. A simple example of a sliding block was used to evaluate the accuracy and rationality of the numerical method. Finally, combined with a deep underground excavation project under complex geological conditions, the stability of the blocks and rock were analyzed. The results indicate that the key blocks are damaged after excavation, the potentially dangerous blocks loosen and undergo large deformations, and the cracks between the blocks and the rock gradually increase as the excavation proceeds. The safety factors of the blocks change during the excavation. The numerical results demonstrate the influence of the surrounding rock on the failure process and on the stability of the blocks, and an effective analysis method is provided for the stability analysis of blocks under complex geological conditions.

Section: Explicit Integration Format That Considers the Contactmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Failure Process and Stability Analysis of Rock Blocks in a Large Underground Excavation Based on a Numerical Method

Xiao

Mathematical Problems in Engineering

2020

“…In the calculation of surrounding rock displacement, selecting the appropriate calculation method and strength criterion can obtain more accurate calculation results. Considering the deformation capacity of surrounding rock, Thirukumaran et al [15] proposed a stability analysis method of tunnel vault rock mass, which can be used to analyze the stability of the surrounding rock. But there is still a large gap between the calculation results of simplifying the vault rock block to a rectangular block and the actual deformation.…”

Section: Introductionmentioning

confidence: 99%

Application of Modified Hoek–Brown Strength Criterion in Water-Rich Soft Rock Tunnel

Deng

Wang

et al. 2021

Geofluids

When a tunnel is excavated in the water-rich soft rock stratum, the strength of the soft rock is greatly reduced due to the seepage of groundwater. The condition may result in engineering accidents, such as large deformation, limit invasion, and even local collapse of the tunnel. Therefore, it is very important to research the stability of the surrounding rock in the water-rich soft rock tunnel. The water-rich disturbance factor considering the seepage influence of groundwater and blasting disturbance is proposed, and the generalized Hoek–Brown strength criterion is modified on the basis of the immersion softening test of soft rock. In accordance with the classical elastic–plastic mechanics theory, the stress, strain, and displacement calculation formulas of the tunnel surrounding rock are derived. The displacement of tunnel surrounding rock is analyzed using the derived formula and the modified Hoek–Brown strength criterion and then compared with the measured value. Results show that the displacement of surrounding rock, which is calculated by modified Hoek–Brown strength criterion considering water-rich disturbance factor and the displacement calculation formula, is close to the measured deformation of surrounding rock in water-rich soft rock tunnel, and the error is small. Therefore, the modified Hoek–Brown strength criterion can be applied to the water-rich soft rock tunnel, and the derived displacement calculation formula can accurately calculate the deformation of tunnel surrounding rock. It is of great significance to the study of surrounding rock stability of water-rich soft rock tunnel.

“…For the surrounding rock of deep underground engineering, the rock mass will undergo shear failure along the structural plane under the action of tectonic stress and seismic load. e shear-slip movement of the rock mass further weakens the bearing capacity and mechanical properties of the rock mass, thereby inducing serious roof deformation and collapse [6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Research Progress on Shear Characteristics of Rock Joints under Constant Normal Stiffness Boundary Conditions

Han

Xiong

Zhou

et al. 2021

Shock and Vibration

The constant normal stiffness (CNS) boundary condition is more representative for the underground engineering, in which the shear-induced dilation is restricted by surrounding rocks, resulting in an increase in the normal stress. Therefore, the use of CNS boundary conditions in the research of shear-slip failure of underground rock engineering is more in line with the actual situation. Taking the instability and failure of surrounding rock in underground engineering as the background, the present study introduces the engineering background of CNS boundary conditions and the research progress on shear characteristics of rock joints under CNS boundary conditions. Three key directions for future research are proposed based on the latest research results of shear characteristics of rock joint under CNS boundary conditions: ① developing a rock joint shear test system that can realize the function of “CNS boundary conditions + shear-seepage test + visualization”; ② carrying out the shear tests of real rock joints under CNS boundary conditions based on 3D scanning and 3D carving technology; and ③ carrying out the shear tests of rock joint network under CNS boundary conditions.