Effect of Intermediate Principal Stress on Cylindrical Tunnel in an Elasto-plastic Rock Mass

A columnar jointed rock mass is a type of rock mass with strong geometric anisotropy and high interface permeability. Its seepage characteristics pose new challenges to the construction and maintenance of the Baihetan Hydropower Station on the Jinsha River. The research object in this study is the columnar jointed rock mass (basalt) in the dam area of Baihetan Hydropower Station. Similar-material model samples of the columnar jointed rock mass with different column dip angles ( α = 0 ° ~90°) were prepared following a similar principle. A true triaxial seepage–stress coupling test was conducted to evaluate the seepage characteristics of similar-material samples with different dip angles under intermediate principal stress and minimum principal stress. The experimental results showed that the columnar jointed rock mass exhibited apparent seepage anisotropy. The relationship curve between the volume flow rate Q and the pressure gradient − d P / d L of the samples with different dip angles showed evident nonlinear seepage under intermediate principal stress, which could be well expressed using the Forchheimer equation. It shows the characteristics of a typical linear Darcy flow under minimum principal stress. The law of variations in the permeability of the samples with different dip angles under intermediate principal stress can be well expressed using the one-dimensional quadratic function equation k = a + b σ 2 + c σ 2 2 , and the law of variations in the permeability of the samples with different dip angles under minimum principal stress can be well expressed using the logarithmic function k = a + b ln σ 3 . The permeabilities of the columnar jointed rock mass with dip angles of 0°, 15°, 30°, and 60° were most sensitive to changes in stress, and the seepage characteristics increased in complexity after changes in stress.

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Finite Element Analysis of Dongjusi Railway Tunnel within Hard Rock Mass Based on the Unified Rock Mass Strength Criterion

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.353-358.2994 ◽

2007 ◽

Vol 353-358 ◽

pp. 2994-2997

Author(s):

Yuan Hua ◽

Tai Quan Zhou ◽

Guo Liang Dai

Keyword(s):

Rock Mass ◽

Principal Stress ◽

Hard Rock ◽

Plastic Material ◽

Strength Criterion ◽

Intermediate Principal Stress ◽

Stress Effect ◽

Railway Tunnel ◽

Rock Mass Strength ◽

Intermediate Principal Stress Effect

The twin shear strength criterion has been proposed to consider the intermediate principal stress effect on the rock mass strength. The unified rock mass strength criterion could consider the intermediate principal stress effect on the rock mass strength. The unified rock mass elasto-plastic material model is implemented in ABAQUS user interface. As a case for study, the stability analysis of Dongjusi railway tunnel within hard rock mass is studied using the unified rock mass strength material. For comparison, the Hoek-Brown empirical strength criterion is also chosen for the rock mass material modeling. The computation results show that the plastic zone calculated using the unified rock mass strength criterion is smaller than that using the Hoek-Brown empirical strength criterion. The railway tunnel lining structure is designed according to the unified rock mass strength criterion and greatly makes use of the rock mass potential strength, which decreases engineering cost.

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The Effect of the Intermediate Principal Stress on the Ground Response of Circular Openings in Rock Mass

Rock Mechanics and Rock Engineering ◽

10.1007/s00603-005-0064-5 ◽

2005 ◽

Vol 39 (2) ◽

pp. 169-181 ◽

Cited By ~ 23

Author(s):

S.-Q. Xu ◽

M.-H. Yu

Keyword(s):

Rock Mass ◽

Principal Stress ◽

Intermediate Principal Stress ◽

Ground Response

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Unified Analytical Solutions of Circular Tunnel Excavated in an Elastic-Brittle-Plastic Rock Mass considering Blast-Induced Damage and Dead Weight Loading

Advances in Civil Engineering ◽

10.1155/2021/5537963 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Yue Cao ◽

Liang Chen ◽

Jinhai Xu ◽

Chong Li ◽

Wei Zhang

Keyword(s):

Rock Mass ◽

Principal Stress ◽

Support System ◽

Fracture Zone ◽

Damage Zone ◽

Intermediate Principal Stress ◽

Circular Tunnel ◽

Tunnel Stability ◽

Stress And Deformation ◽

Zone Radius

Stress and deformation around circular tunnel are crucial for optimizing the support system and evaluating the tunnel stability. The damage zone induced by blasting or mechanical excavation can dramatically influence the support design and methods because the self-weight of broken rock mass at the roof of the tunnel can exert a high pressure on the support system, leading to the support system instability due to the overload. This paper presents a new closed-form solution for analyzing the stress and deformation of deep circular tunnel excavated in elastic-brittle rock mass with the consideration of the rock gravity and damage zone by using the unified strength criterion. A new modified equilibrium equation in the fracture zone is used to determine the stress and the radius of fracture zone. The correctness of the solution is also verified by comparison with the numerical simulation results. The results illustrate that the rock gravity, damage zone radius, and intermediate principal stress have an extremely important influence on the ground response. The tunnel surface convergence and damage zone radius with the consideration of the gravity are obviously larger than those without consideration of the gravity. The rock gravity effect under the high intermediate principal stress gradually weakens, illustrating that the intermediate principal stress is beneficial to tunnel stability. Large deformation instability of the tunnel is dependent on the extension of damage zone. The larger the radius of damage zone, the larger both fracture range and tunnel surface deformation. The proposed solution in this study is novel and can be used to assess the ground convergence for different scenarios and to optimize the support system during the early design stage of the tunnel.

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