Difference solution for a circular tunnel excavated in strain-softening rock mass considering decayed confinement

Wang, Fengyun; De-ling, Qian

doi:10.1016/j.tust.2018.08.001

Cited by 25 publications

(10 citation statements)

References 27 publications

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“…In Equation ( 21), E is Young's modulus and v is Poisson's ratio. Therefore, the change in the strength parameter ω in the plastic softening zone, along with the softening parameter, satisfies the following formula [24,32,33]:…”

Section: Calculation Of Rock Mass Deformation In the Elastic Regionmentioning

confidence: 99%

“…The present study investigated the effectiveness of the proposed algorithm by comparing the results of the proposed algorithm with those of Lee [24] and Wang [32]. The proposed algorithm was applied to a circular tunnel with an excavation radius r 0 = 3 m. The input data were E = 10 GPa, v = 0.25, σ 0 = 20 MPa, ϕ p = 30, ϕ r = 22, c p = 1 MPa, c r = 0.7 MPa, φ p = 3.75…”

Section: Verification Of the Proposed Algorithmmentioning

confidence: 99%

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A Proposed Algorithm to Compute the Stress-Strain Plastic Region and Displacement of a Deep-Lying Tunnel Considering Intermediate Stress and Strain-Softening Behavior

Shen

et al. 2021

Applied Sciences

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Past studies on deep-lying tunnels under the assumption of plane strain have generally neglected the influence of intermediate principal stress even though this affects the surrounding rocks in the plastic zone. This study proposes a finite difference method to compute the stress strain plastic region and displacement of a tunnel based on the Drucker–Prager (D–P) yield criterion and non-associated flow rule and considering the influences of intermediate principal stress and the strain-softening behavior of surrounding rock. The computed results were compared with those of other well-known solutions and the accuracy and validity of the method were confirmed through some examples. Parameter analysis was conducted to investigate the effects of intermediate principal stress on stress-strain, the plastic region, the ground response curve, and the dilatability of surrounding rock. The results showed that the plastic radius , the residual radius , and radial displacement of surrounding rock first decreased and then increased with increasing intermediate principal stress coefficient b from 0 to 1, with the minimums occurring at b = 0.75. On the contrary, the peak and rate of variation of the dilatancy coefficient first increased and then decreased with increasing b and the dilatancy coefficient gradually transitioned from nonlinear to linear variation. Meanwhile, the inhibition of the plastic radius and radial displacement gradually weakened with increasing support pressure, whereas the dilatancy coefficient of the tunnel opening gradually increased.

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Section: Calculation Of Rock Mass Deformation In the Elastic Regionmentioning

confidence: 99%

Section: Verification Of the Proposed Algorithmmentioning

confidence: 99%

A Proposed Algorithm to Compute the Stress-Strain Plastic Region and Displacement of a Deep-Lying Tunnel Considering Intermediate Stress and Strain-Softening Behavior

Shen

et al. 2021

Applied Sciences

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“…At great depth with strong deep structural activity or high deformability, rock squeezing may occur, and the repair rate of large deformed roadways can reach 70% [2,3]. In the deep coal mining, due to the influences of "three high and one disturbance" (high geo-stress, high ground temperature, high permeable pressure, and the disturbance of mining activities), the unique stress characteristic and plastic yielding were engendered by the mechanics of roadway [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

“…What is more, the elasto-plastic, elasto-brittle-plastic, and strain-softening models have been built based on Mohr-Coulomb (M-C) and Hoek-Brown (H-B) criteria [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][32][33][34][35][36]. The Mohr-Coulomb criterion is linear which is relatively convenient to use, but the criterion does not reflect the nonlinear destruction characteristics of rock bodies.…”

Section: Introductionmentioning

confidence: 99%

The Elastoplastic Solutions of Deep Buried Roadway Based on the Generalized 3D Hoek-Brown Strength Criterion considering Strain-Softening Properties

et al. 2021

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The deep underground roadways are widely used in the mining industries at present, but the relevant theoretical bases are not fully understood. In this paper, the numerical solutions for strain-softening surrounding rock under the generalized three-dimensional (3D) Hoek-Brown (GZZ) strength criterion are developed incorporating the confinement-dependent characteristics of ψ and η ∗ and their influences on the stress and displacement of equivalent circular roadway. On the basic of a finite difference, method for the strain-softening model is proposed to consider the variation of ψ and η ∗ in analyzing the strain-softening behavior of rock masses. Combining the equilibrium equation and strength criterion, the stress conditions for each annulus are calculated analytically. The displacement for each step is obtained analytically by solving the differential equation through invoking flow rule and Hooke’s law. The accuracy of the proposed method is verified through the comparison between the results and the previous studies. The effect of intermediate principal stress of GZZ strength criterion is considered; the rationality of the proposed method is verified by two aspects. First, by comparing with the two-dimensional narrow and generalized H-B strength criterion, the advantage of GZZ strength criterion that considers the effect intermediate main stress is highlighted. On the other hand, compared with the three-dimensional linear D-P criterion, the advantage of GZZ strength criterion in the theoretical research of deep underground roadway in coal mine is highlighted. The results show that the strain-softening of the surrounding rock in the plastic zone of the roadway can reduce the pressure of the surrounding rock, but it will greatly increase its deformation. In the high field stress areas, the strain-softening of surrounding rock is the key reason for the destruction of the roadway. It is suggested that in the design and calculation of the support system of the roadway, the strain-softening characteristics of the surrounding rock should be considered, which is very important to avoid large deformation and damage of roadway.

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“…Many rock mechanical tests [19][20][21] show that a rock mass exhibits significant dilatancy in the post-peak stage and that the dilation angle strongly depends on the confining stress and plastic shear strain, decreasing nonlinearly with an increase in the confining stress or plastic shear strain. The surrounding rock of a deep tunnel has a large post-peak zone under high in-situ stress conditions [22,23], and strain softening and dilatancy, as the two main characteristics of the post-peak mechanical behavior of a rock mass, show a significant synergistic effect [24]; thus, they should both be accurately considered in a deep tunnel analysis [25].…”

Section: Introductionmentioning

confidence: 99%

Effect of Axial In-Situ Stress in Deep Tunnel Analysis Considering Strain Softening and Dilatancy

Liu

Lü

et al. 2020

Energies

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In many previous tunnel analyses, the axial in-situ stress was ignored. In this work, its effect on the deformation and failure of the surrounding rock of a deep tunnel was revealed, considering the objective strain softening and dilatancy behavior of the surrounding rock. Analysis based on the incremental plastic flow theory was conducted, and C++ was used to write a constitutive model for numerical simulation to verify and further analyze this effect. Then, the results were validated by the field monitoring data of a coal mine gateway. Results show that the effect of the axial in-situ stress σa0 is more significant when strain softening is considered, compared with the results of a perfectly elastoplastic model. When the axial stress σa is σ1 or σ3 at the initial yield, an increase or decrease in σa0 intensifies the deformation and failure of the surrounding rock. When σa is σ2 at the initial yield, 3D plastic flow partly controlled by σa may occur, and an increase in σa0 intensifies the deformation and failure of the surrounding rock. The effect of σa0 will be amplified by considering dilatancy. Considering both strain softening and dilatancy, when σa0 is close to the tangential in-situ stress σt0 or significantly greater than σt0 (1.5 times), σa will be σ2 or σ1 at the initial yield, and then 3D plastic flow will occur. In the deformation prediction and support design of a deep tunnel, σa0 should not be ignored, and the strain softening and dilatancy behavior of the surrounding rock should be accurately considered.

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Difference solution for a circular tunnel excavated in strain-softening rock mass considering decayed confinement

Cited by 25 publications

References 27 publications

A Proposed Algorithm to Compute the Stress-Strain Plastic Region and Displacement of a Deep-Lying Tunnel Considering Intermediate Stress and Strain-Softening Behavior

A Proposed Algorithm to Compute the Stress-Strain Plastic Region and Displacement of a Deep-Lying Tunnel Considering Intermediate Stress and Strain-Softening Behavior

The Elastoplastic Solutions of Deep Buried Roadway Based on the Generalized 3D Hoek-Brown Strength Criterion considering Strain-Softening Properties

Effect of Axial In-Situ Stress in Deep Tunnel Analysis Considering Strain Softening and Dilatancy

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