scholarly journals Elastoplastic Analysis for Circular Tunnel Based on Modified Lade Criterion considering Strain Softening and Dilatancy

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yansheng Deng ◽  
Jianxiu Wang ◽  
Baoping Zou
Keyword(s):  
Plastic Zone ◽  
Strain Softening ◽  
Pressure Coefficient ◽  
Numerical Procedure ◽  
Strength Properties ◽  
In Situ Stress ◽  
Circular Tunnel ◽  
Negative Power ◽  
Softening Behavior ◽  
Zone Radius

Modified Lade criterion can not only describe the strength properties of many kinds of rocks well but also has simple and practical parameters. Although the elastoplastic solution of circular tunnel has been extensively investigated, the method based on modified Lade criterion considering the effect of the intermediate principal stress, strain-softening behavior, and dilatancy has not yet been studied. In this paper, a new numerical procedure based on modified Lade criterion is proposed to calculate the elastoplastic solutions for surrounding rock of the circular tunnel. The comparisons of stress, displacement, and plastic zone radius are carried out between the presented method and published literatures under axisymmetric and nonaxisymmetric original in situ stress field. Finally, a series of parametric analyses are executed and discussed. It can be concluded that the lateral pressure coefficient, λ, influences both the size of plastic zone and the development direction. The plastic zone radius shows a negative power function change with increasing critical deviatoric plastic strain and increases slightly with increasing dilation angle, ψ.

Rock Failure Analysis of the Broken Zone Around a Circular Opening / Analiza pęknięcia skały w strefie naruszonej wokół otworu kolistego

2013 ◽  
Vol 58 (1) ◽  
pp. 165-188 ◽  
Author(s):  
Hossein Ali Lazemi ◽  
Mohammad Fatehi Marji ◽  
Ali Reza Yarahmadi Bafghi ◽  
Kamran Goshtasbi
Keyword(s):  
Plastic Zone ◽  
Failure Criterion ◽  
In Situ Stress ◽  
Circular Tunnel ◽  
In Situ Stresses ◽  
Stress Components ◽  
Plastic Rock ◽  
Coulomb Criterion ◽  
Zone Radius

In this paper, considering the non-linear Hoek-Brown failure criterion, a new theoretical model is presented to predict the stress components and estimate the plastic zone radius around a circular tunnel. The tunnel is excavated in an elasto-plastic rock mass subjected to plane hydrostatic and axial in situ stresses. Effects of the axial in situ stress on the plastic zone radius and stress components are studied. Based on the combination of plane hydrostatic and axial in situ stresses with the equilibrium equation and a suitable failure criterion (Hoek & Brown failure criterion), several cases are considered. For each case, the stress components, the plastic zone radius and the necessary conditions for its occurrence are determined. The results obtained by the present method are compared with those using Mohr-Coulomb criterion and with the experimental data, illustrating the validity of the present model in predicting the failure zone radius.

Analysis of Plastic-Zone Radius Influenced by Mechanical Parameters in Tunnel Excavation and Support

2012 ◽  
Vol 238 ◽  
pp. 787-790
Author(s):  
Zhong Ming Su ◽  
Rui Liu
Keyword(s):  
Plastic Zone ◽  
Axial Force ◽  
Analytical Formula ◽  
Mechanical Parameters ◽  
Circular Tunnel ◽  
Tunnel Excavation ◽  
Dynamic Design ◽  
Elastic Plastic ◽  
Zone Radius ◽  
Plastic Theory

According to the elastic-plastic theory, the analytical formula of plastic zone radius is established for circular tunnel in its excavation and support, and the effect of anchor support is verified based on the radius of plastic zone from the perspective of measured axial force. The influences to plastic zone by the variations of mechanical parameters and resistance of support are quantitatively analyzed. The result is of great significance to the monitoring measurement and the dynamic design and construction of tunnel.

scholarly journals Semianalytical Solution for Large Deformation of Salt Cavern with Strain-Softening Behavior

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Lina Ran ◽  
Huabin Zhang ◽  
Qingqing Zhang
Keyword(s):  
Plastic Zone ◽  
Large Deformation ◽  
Strain Softening ◽  
Structural Characteristics ◽  
Strength Criterion ◽  
Geological Strength Index ◽  
Salt Rock ◽  
Salt Cavern ◽  
Softening Behavior ◽  
The Impact

A semianalytical solution of stress and displacement in the strain-softening and plastic flow zones of a salt cavern is presented. The solution is derived by adopting the large deformation theory, considering the nonlinear Hoek–Brown (H-B) strength criterion. The Romberg method is used to carry out numerical calculation, and then, the large deformation law of displacement is analyzed. The results are compared with those obtained by former numerical methods, and the solutions are validated. The results indicate that the displacement of the plastic zone decreases with the increase in distance away from the salt cavern. Similarly, it decreases with an increase in the geological strength index or running pressure, with the running pressure having a more significant effect on the displacement. It increases with the dilation angle, and the impact degree gradually increases. Compared with the softening parameter, h, of the plastic zone, the flow parameter, f, has little impact on the displacement. The displacement of the plastic zone obviously increased when considering the strain-softening of salt rock. When considering the shear dilation and softening behaviors of salt rock, the analytical solution obtained by employing the experiential regression Hoek–Brown (H-B) criterion, which considers many factors such as the structural characteristics of the salt formation and the rock mass quality, is safer and closer to the actual situation. This study can provide reference for many applications, including but not confined to analyzing the deformation of the surrounding rock of an underground salt cavern storage facility during construction.

scholarly journals A New Unified Solution for Circular Tunnels Based on Generalized SMP Criterion considering the Strain Softening and Dilatancy

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Qifeng Guo ◽  
Jiliang Pan ◽  
Xinghui Wu ◽  
Xun Xi ◽  
Meifeng Cai
Keyword(s):  
Internal Friction ◽  
Plastic Zone ◽  
Strain Softening ◽  
Friction Angle ◽  
Surrounding Rock ◽  
Internal Friction Angle ◽  
Plastic State ◽  
Circular Tunnel ◽  
Dilatancy Angle ◽  
Elastic Plastic

According to the strain-softening characteristics of rock mass, an ideal elastic strain-softening model is developed, and the surrounding rock of tunnels is subdivided into the plastic broken zone, plastic strain-softening zone, and elastic zone. Based on the generalized spatially mobilized plane criterion, an elastic-plastic analytical solution of a circular tunnel is derived. The effects of intermediate principal stress, strain softening, and dilatancy are considered in the unified solution. The stress, displacement, and plastic zone radius of surrounding rock based on the SMP criterion are compared with those based on the Mohr–Coulomb criterion. Furthermore, the effects of parameters such as the softening modulus, dilatancy angle, and internal friction angle on the deformation and stress of tunnels are discussed. It has been found that the larger the dilatancy angle is, the larger the plastic zone displacement and the radius of the broken zone are. The larger the internal friction angle, the smaller the sizes of the plastic zone, the strain-softening zone, and the broken zone are. The deformation of surrounding rock in the broken zone is more sensitive to the internal friction angle than that in the strain-softening zone. The unified solution based on the SMP criterion provides a well understanding for the elastic-plastic state of tunnels, which can be the guidance for tunnel excavations and support designs.

scholarly journals An Improved Stress and Strain Increment Approaches for Circular Tunnel in Strain-Softening Surrounding Rock Considering Seepage Force

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Ling Wang ◽  
Jin-feng Zou ◽  
Yu-ming Sheng
Keyword(s):  
Rock Mass ◽  
Plastic Zone ◽  
Radial Displacement ◽  
Axisymmetric Problem ◽  
Strain Softening ◽  
Strain Increment ◽  
Surrounding Rock ◽  
Stress And Strain ◽  
Seepage Force ◽  
Circular Tunnel

Considering the effect of seepage force, a dimensionless approach was introduced to improve the stress and strain increment approach on the stresses and radial displacement around a circular tunnel excavated in a strain-softening generalized Hoek–Brown or Mohr–Coulomb rock mass. The circular tunnel can be simplified as axisymmetric problem, and the plastic zone was divided into a finite number of concentric rings which satisfy the equilibrium and compatibility equations. Increments of stresses and strains for each ring were obtained by solving the equilibrium and compatibility equations. Then, the stresses and displacements in softening zone can be calculated. The correctness and reliability of the proposed approach were performed by the existing solutions.

scholarly journals Analysis of plastic zones in surrounding rocks around a circular tunnel considering the effect of intermediate principal stress and heterogeneity

2019 ◽  
Vol 275 ◽  
pp. 03007 ◽  
Author(s):  
Shuxin Deng ◽  
Yonglai Zheng ◽  
Lipo Feng ◽  
Le Van Tuan ◽  
Cuizhou Yue ◽  
...  
Keyword(s):  
Plastic Zone ◽  
Principal Stress ◽  
Lateral Pressure ◽  
Pressure Coefficient ◽  
Plastic Zone Size ◽  
Intermediate Principal Stress ◽  
Circular Tunnel ◽  
Lateral Pressure Coefficient ◽  
Calculation Results ◽  
Coulomb Criterion

Based on a modified Mohr-Coulomb criterion with a non-uniform coefficient, a calculation method of plastic zone boundary of surrounding rocks in a circular tunnel in non-uniform stress field is established. Both the effects of intermediate principal stress and heterogeneity are studied. With the increase of the intermediate principal stress, the plastic zone size of the surrounding rocks will decrease first and then increase. Lateral pressure coefficient has an effect on the shape of the plastic zone. With the increase of lateral pressure coefficient, the plastic zone gradually becomes uniform, and the failure of surrounding rock develops upward and downward from both sides. As non-uniform coefficient increases, the material is more uniform and the effect of intermediate principal stress on the plastic zone is less significant. If the effect of intermediate principal stress is not taken into account, the calculation results tend to be consistent with results calculated by the Mohr-Coulomb criterion, which are considered to be conservative.

Comparison of Shape Characteristics of Plastic Zone Around Circular Tunnel Under Different Strength Criteria

2020 ◽  
Vol 36 (6) ◽  
pp. 849-856
Author(s):  
H. Y. Shi ◽  
Z. K. Ma ◽  
Q. J. Zhu ◽  
J. J. Shi ◽  
Z. Q. Zhao
Keyword(s):  
Plastic Zone ◽  
Lateral Pressure ◽  
Pressure Coefficient ◽  
Strength Criterion ◽  
Stress Change ◽  
Circular Tunnel ◽  
Strength Criteria ◽  
Lateral Pressure Coefficient ◽  
Low Sensitivity ◽  
Shape Characteristics

ABSTRACTThe butterfly plastic zone theory based on Mohr Coulomb criterion has been widely used in coal mine production. In order to verify the universality of the theory, it is necessary to compare the distribution of plastic zone under different strength criteria. Based on the elastic-plastic mechanics, the principal stress distribution function around the circular tunnel is deduced in the paper, and the boundary and radius of the plastic zone under different strength criteria are calculated. The results show that the change laws of the plastic zone around the circular tunnel under different strength criteria has the following commonness: firstly, with the increase of the lateral pressure coefficient, the shape of the plastic zone presents the change laws of “circle ellipse butterfly”; Secondly, with the increase of the lateral pressure coefficient, the radius of the plastic zone is exponential distribution, while the characteristic value is different when the radius of the plastic zone is infinite. At same time, it shows that the butterfly plastic zone has a low sensitivity dependence on the strength criterion, no matter which strength criterion is adopted, and the butterfly plastic zone will inevitably appear in the surrounding rock mass of circular tunnel in the high deviator stress environment; The plastic zone with butterfly shape is highly sensitive to the stress change, and the small stress change may promote the expansion of the plastic zone. This result is significant for us to understand and prevent rock engineering disasters and accidents.

scholarly journals Mechanical Analysis of the Circular Tunnel considering the Interaction between the Ground Response Curve and Support Response Curve

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Tianming Su ◽  
Hanyu Peng ◽  
Hongyan Liu
Keyword(s):  
Plastic Zone ◽  
Radial Displacement ◽  
Response Curve ◽  
Mechanical Analysis ◽  
Surrounding Rock ◽  
Elastic Displacement ◽  
Circular Tunnel ◽  
Ground Response ◽  
Support Structure ◽  
Zone Radius

The viewpoint that the ground initial elastic displacement and the interaction between the ground response curve (GRC) and support response curve (SRC) in the surrounding rock should be considered at the same time in the mechanical analysis of the circular tunnel is proposed, and its solution method is also established. Meanwhile, in order to consider the effect of the intermediate principle stress, Drucker-Prager criterion is introduced to describe the yield property of the surrounding rock. The calculation example indicates that the final radial displacement of the tunnel circumference will increase when the ground initial elastic displacement in the surrounding rock is considered before the support structure is applied, which indicates that it is necessary to consider the ground initial elastic displacement in the surrounding rock before the support structure is applied. With increasing the support resistance force and the initial field stress, the plastic zone radius in the surrounding rock and the radial displacement of the tunnel circumference will decrease and increase, respectively, while with increasing the rock internal friction angle and cohesion, the plastic zone radius in the surrounding rock and the radial displacement of the tunnel circumference both decrease. Meanwhile, with the stress Lode parameter increasing from −1 to 1, the plastic zone radius in the surrounding rock and the radial displacement of the tunnel circumference both greatly decrease and then slightly increase. It indicates that the intermediate principle stress has some effect on the calculation results.

scholarly journals Numerical Study on Damage Zones Induced by Excavation and Ventilation in a High-Temperature Tunnel at Depth

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4773
Author(s):  
Jianyu Li ◽  
Hong Li ◽  
Zheming Zhu ◽  
Ye Tao ◽  
Chun’an Tang
Keyword(s):  
High Temperature ◽  
Lateral Pressure ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Fracture Morphology ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
Geothermal System ◽  
Mechanical Coupling ◽  
Lateral Pressure Coefficient

Geothermal power is being regarded as depending on techniques derived from hydrocarbon production in worldwide current strategy. However, it has artificially been developed far less than its natural potentials due to technical restrictions. This paper introduces the Enhanced Geothermal System based on Excavation (EGS-E), which is an innovative scheme of geothermal energy extraction. Then, based on cohesion-weakening-friction-strengthening model (CWFS) and literature investigation of granite test at high temperature, the initiation, propagation of excavation damaged zones (EDZs) under unloading and the EDZs scale in EGS-E closed to hydrostatic pressure state is studied. Finally, we have a discussion about the further evolution of surrounding rock stress and EDZs during ventilation is studied by thermal-mechanical coupling. The results show that the influence of high temperature damage on the mechanical parameters of granite should be considered; Lateral pressure coefficient affects the fracture morphology and scale of tunnel surrounding rock, and EDZs area is larger when the lateral pressure coefficient is 1.0 or 1.2; Ventilation of high temperature and high in-situ stress tunnel have a significant effect on the EDZs scale; Additional tensile stress is generated in the shallow of tunnel surrounding rock, and the compressive stress concentration transfers to the deep. EDZs experiences three expansion stages of slow, rapid and deceleration with cooling time, and the thermal insulation layer prolongs the slow growth stage.

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