Discussions on Zonal Disintegration around Tunnel in Deep Rock Mass

2012 ◽  
Vol 594-597 ◽  
pp. 2285-2289 ◽  
Author(s):  
Peng Jia ◽  
Tian Hong Yang ◽  
Chun Ming Zhang
Keyword(s):  
Rock Mass ◽  
Laboratory Test ◽  
Stress Level ◽  
Hydrostatic Stress ◽  
Axial Stress ◽  
Numerical Code ◽  
Zonal Disintegration ◽  
Heterogeneous Rock ◽  
Deep Rock ◽  
Adjacent Fractures

Questions related to zonal disintegration such as difference between results from laboratory test and field monitoring test, as well as the effect of multi-axial stress level on zonal disintegration were discussed through numerical modeling by using a 3D numerical code called RFPA3D. Results show that the much smaller fracture spacing captured by laboratory test on zonal disintegration is due to the heterogeneity extent of the tested material. Zonal disintegration is an inherent character of heterogeneous rock mass, the more the heterogeneous the rock is, the larger the spacing between the adjacent fractures will be. The configuration of zonal disintegration is influenced by combination of stress level in three directions. Intact fracture rings can not be formed unless a nearly hydrostatic stress state exists in directions perpendicular to tunnel axis.

scholarly journals Study on the Generation Mechanism and Development Law of the Zonal Disintegration in Deep Burial Tunnels

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Xiaohui Ma ◽  
Jihong Wei ◽  
Jin Liu ◽  
Zezhuo Song ◽  
Yuxia Bai
Keyword(s):  
Mechanical Properties ◽  
Rock Mass ◽  
Maximum Stress ◽  
Axial Stress ◽  
Axial Direction ◽  
Tensile Failure ◽  
Zonal Disintegration ◽  
Nonlinear Characteristics ◽  
Deep Rock ◽  
New Phenomena

In the development of underground spaces, we found that the mechanical properties of rock mass often demonstrate strong nonlinear characteristics. Some new phenomena emerge in deep rock mass engineering. This includes zonal disintegration and rock burst. Zonal disintegration is very important in deep tunnels. In this paper, we start with the mechanical properties of deep rocks to understand the preconditions for zonal disintegration. Using the Failure Approach Index (FAI), the process of zonal disintegration can be modeled by FLAC (FISH language). Our results indicate that tensile failure in the Supporting Pressure Zone (SPZ) is a precondition for zonal disintegration. Various factors that affect the generation of zonal disintegration are studied. When the maximum stress is in the axial direction, zonal disintegration will be present in deep tunnels. The high axial stress is necessary for zonal disintegration. We will present a zonal disintegration simulation in one coal mine for comparison with the borehole teleview data. We suggest some measures to prevent the development of zonal disintegration.

Numerical Study on Zonal Disintegration of Deep Rock Mass Using Three-Dimensional Bonded Block Model

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Qingteng Tang ◽  
Wenbing Xie ◽  
Xingkai Wang ◽  
Zhili Su ◽  
Jinhai Xu
Keyword(s):  
Rock Mass ◽  
Fracture Zone ◽  
Numerical Study ◽  
Confining Pressure ◽  
Surrounding Rock ◽  
Zonal Disintegration ◽  
Block Model ◽  
Deep Rock Mass ◽  
Damaged Zone ◽  
Deep Rock

Zonal disintegration, a phenomenon of fractured zones and intact zones distributed alternately in deep rock mass, is different from the excavation-damaged zone of shallow rock mass. In this study, bonded block model of 3DEC was employed to study the fracture mode and origination condition of zonal disintegration. Initiation, propagation, and coalescence progress of fracture around the roadway boundary under different triaxial stress conditions are elaborated. Numerical simulation demonstrated that zonal disintegration may occur when the direction of maximum principal stress is parallel to the roadway axis. It is interesting to find that the fracture around the roadway boundary traced the line of a spiral line, while slip-line fractures distributed apart from the roadway boundary. The extent of the alternate fracture zone decreased as the confining pressure increased, and alternate fracture zone was no longer in existence when the confining pressure reaches a certain value. Effects of roadway shape on zonal disintegration were also studied, and the results indicated that the curvature of the fracture track line tends to be equal to the roadway boundary in shallow surrounding rock of the roadway, while the fractures in deep surrounding rock seems unaffected by the roadway shape. Those findings are of great significance to support design of deep underground openings.

scholarly journals Strain-Softening Analyses of a Circular Bore under the Influence of Axial Stress

2021 ◽  
Vol 11 (17) ◽  
pp. 7937
Author(s):  
Xuechao Dong ◽  
Mingwei Guo ◽  
Shuilin Wang
Keyword(s):  
Rock Mass ◽  
Plane Stress ◽  
Strain Softening ◽  
Hydrostatic Stress ◽  
Axial Stress ◽  
Perfectly Plastic ◽  
Out Of Plane ◽  
Softening Process ◽  
Elastic Perfectly Plastic ◽  
Proper Consideration

Strain-softening analyses were performed around a circular bore in a Mohr–Coulomb rock mass subjected to a hydrostatic stress field in cross section and out-of-plane stress along the axis of the bore. Numerical procedures that simplify the strain-softening process in a step manner were employed, and on the basis of the theoretical solutions of the elastic–brittle–plastic(EBP) medium, the strain-softening results of the displacements, stresses and the plastic zones around the circular bore were obtained. The numerical solution was validated based on the fact that the strain-softening process became EBP when the softening slope was very steep and elastic-perfectly plastic(EP) when the softening slope was near zero. The results illustrated that the stresses and displacements in the rock mass surrounding the bore was affected by axial stress and that a proper consideration of out-of-plane stress is necessary. Moreover, the presented results can be used for the verification of numerical codes.

scholarly journals Geomechanical characterization of a heterogenous rock mass using geological and laboratory test results: a case study of the Niobec Mine, Quebec (Canada)

2021 ◽  
Vol 3 (6) ◽  
Author(s):  
Shahriyar Heidarzadeh ◽  
Ali Saeidi ◽  
Catherine Lavoie ◽  
Alain Rouleau
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Rock Mass ◽  
Laboratory Test ◽  
Rock Unit ◽  
Geomechanical Parameters ◽  
Characterization Study ◽  
Heterogeneous Rock ◽  
Geomechanical Characterization

Abstract To conduct a successful geomechanical characterization of rock masses, an appropriate interpretation of lithological heterogeneity should be attained by considering both the geological and geomechanical data. In order to clarify the reliability and applicability of geological surveys for rock mechanics purposes, a geomechanical characterization study is conducted on the heterogeneous rock mass of Niobec Mine (Quebec, Canada), by considering the characteristics of its various identified lithological units. The results of previous field and laboratory test campaigns were used to quantify the variability associated to intact rock geomechanical parameters for the different present lithological units. The interpretation of geomechanical similarities between the lithological units resulted in determination of three main rock units (carbonatite, syenite, and carbonatite-syenite units). Geomechanical parameters of these rock units and their associated variabilities are utilized for stochastic estimation of geomechanical parameters of the heterogeneous rock mass using the Monte Carlo Simulation method. A comparison is also made between the results of probabilistic and deterministic analyses to highlight the presence of intrinsic variability associated with the heterogeneous rock mass properties. The results indicated that, for the case of Niobec Mine, the carbonatite-syenite rock unit could be considered as a valid representative of the entire rock mass geology since it offers an appropriate geomechanical approximation of all the present lithological units at the mine site, in terms of both the magnitude and dispersion of the strength and deformability parameters. Article Highlights Evaluating the reliability and applicability of geological survey outcomes for rock mechanics purposes. A geomechanical characterization study is conducted on the heterogeneous rock mass by considering the various identified rock lithotypes. The geomechanical parameters of intact units and their associated variabilities are used to stochastically estimate the geomechanical parameters of the heterogeneous rock mass by employing the Monte Carlo Simulation. A comparison is also made between the results of probabilistic and deterministic geomechanical analyses. The results indicate that, in the case of Niobec Mine, the combined syenite-carbonatite rock unit could be considered as a valid representative of the entire rock mass.

scholarly journals Research on Failure Mechanism and Parameter Sensitivity of Zonal Disintegration in Deep Tunnel

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Xutao Zhang ◽  
Qiang Gao ◽  
Shicai Cui ◽  
Changrui Duan
Keyword(s):  
Rock Mass ◽  
Failure Mechanism ◽  
Deformation Modulus ◽  
Morphological Characteristics ◽  
Zonal Disintegration ◽  
Deep Tunnel ◽  
Equilibrium Equations ◽  
Distribution Law ◽  
Deep Rock Mass ◽  
Deep Rock

With the increase of excavation depth, the zonal disintegration phenomenon appears in the deep rock mass, which is quite different from the failure mode of shallow tunnel. In order to analyse the failure mechanism of this phenomenon, an elastoplastic softening damage model was put forward based on the softening damage characteristics of deep rock mass. The constitutive equations, the equilibrium equations, and the failure criterion were deduced. The theoretical solutions of radial displacement and radial stresses and tangential stresses of deep surrounding rock mass were calculated. The distribution law of zonal disintegration in deep tunnel was obtained. The theoretical solutions presented an oscillating mode. The theoretical calculated widths of fracture zones were in good agreement with the in situ test data. Besides, the sensitivity of different parameters to fracture morphology was calculated and analysed. The results show that the relative loading strength has a controlling role in the zonal disintegration morphology, followed by the cohesion force and deformation modulus, and the internal friction angle is the least. This study reveals the morphological characteristics and influencing factors of zonal disintegration, which provides a basis for the prediction and support control of fracture modes.

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