scholarly journals Geomechanical Model Experiment Study on Deformation and Failure Mechanism of the Mountain Tunnel in Layered Jointed Rock Mass

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Zhibiao Guo ◽  
Jinyan Fan ◽  
Fengnian Wang ◽  
Hongbo Zhou ◽  
Wei Li
Keyword(s):  
Rock Mass ◽  
Failure Mechanism ◽  
Model Test ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Physical Model Test ◽  
Correlation Technique ◽  
Large Area ◽  
Rock Mass Structure ◽  
Deformation And Failure

The Minxian tunnel is a key engineering of the Weiyuan-Wudu expressway that is excavated in layered jointed carbonaceous slate rock mass. During the construction process, the surrounding rocks of the tunnel encountered serious large deformations and failure, which brought about great difficulties to the safety and cost of the tunnel. In order to study the deformation and failure mechanism of the surrounding rocks, a physical model test was conducted, and integrated methods including strain gauges, a digital camera, and noncontact full-field digital imaging correlation technique were used to record the response information of the surrounding rocks. The evolution process of surrounding rocks failure was simulated successfully in the model test, and the deformation characteristics were basically consistent with the actual engineering. The modelling results show that concentrated stresses in the surrounding rocks were very uneven due to developed stratified and jointed rock mass structure. The maximum and minimum concentrated stresses appeared at the vault of the tunnel and left of inverted arc area, and concentration factors were 3.11 and 1.98, respectively. The main forms of surrounding rocks deformation and failure were large area spalling of surface, severe circumferential fractures, serious bending deformations of thin rock layers, and collapse of overlying strata. The maximum displacements occurred at left sidewall and right shoulder of the tunnel and the corresponding actual displacements were 460 mm to 500 mm. Caving and failure took place firstly at several key positions with maximum concentrated stresses or displacements and subsequently gave rise to massive collapse of surrounding rocks.

Anisotropic characteristic of irregular columnar-jointed rock mass based on physical model test

2016 ◽  
Vol 21 (5) ◽  
pp. 1728-1734 ◽  
Author(s):  
Zhinan Lin ◽  
Weiya Xu ◽  
Huanling Wang ◽  
Jiuchang Zhang ◽  
Wang Wei ◽  
...  
Keyword(s):  
Rock Mass ◽  
Physical Model ◽  
Model Test ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Physical Model Test ◽  
Columnar Jointed Rock Mass

Effect of support characteristics on the earth pressure in a jointed rock mass

2015 ◽  
Vol 52 (12) ◽  
pp. 1956-1967 ◽  
Author(s):  
Moorak Son ◽  
Solomon Adedokun
Keyword(s):  
Rock Mass ◽  
Earth Pressure ◽  
Numerical Approach ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Physical Model Test ◽  
Joint Shear Strength ◽  
Rock Stratum ◽  
Rock Types ◽  
The Earth

This study examines the magnitude and distribution of earth pressures against a support system in a jointed rock mass according to the support characteristics (strut stiffness and spacing), different rock types, and joint conditions (joint shear strength and joint inclination angle). A series of numerical parametric analyses were performed after verifying the numerical approach through a physical model test. These analyses were based on the discrete element method, which can take into account the joint characteristics of the rock strata and the interactions between the ground and the retaining structure. The results were compared with Peck’s earth pressure for soil ground, which showed that the magnitude and distribution of earth pressure are strongly affected by the support characteristics, rock types, and joint conditions, and that the earth pressure in the rock stratum can be significantly different from that in the soil ground. The results suggest that the support characteristics, including the rock types and joint conditions, are important factors affecting the earth pressure, and should be considered for the safe and economic design and construction of retaining structures in a jointed rock mass.

The Failure Mechanism Research of Jointed Rock Mass Slope

2011 ◽  
Vol 94-96 ◽  
pp. 1166-1170
Author(s):  
Zhen Qiang Ni ◽  
Ji Ming Kong ◽  
A. Fayou
Keyword(s):  
Rock Mass ◽  
Failure Mechanism ◽  
Compressive Stress ◽  
Yield Criterion ◽  
Jointed Rock ◽  
Geological Structure ◽  
Level Line ◽  
Jointed Rock Mass ◽  
Maximum Compressive Stress ◽  
Geological Body

It was difficult to analyze the stability of the rock slope for its complex geological structure. Rock mass was the geological body that subjected to intense deformation and suffered damage, which was composed by rock and jointed rock mass. When the rock mass was in the high steep rock, its loading state was further complicated. First we analyzed the failure mechanism of jointed rock mass in theory, and we used Flac3d with the Mohr-Coulomb yield criterion to simulate the displacements and stresses. We built three models that included angles with level line were 25°, 45° and 65°. The results showed that, all around the joints stresses concentration occurred, the maximum compressive stress occurred at the crack tip; the final crack direction always tended to the direction of maximum compressive stress; and when the angle was bigger, before the crack expended further, the strength of rock decreased first, and destroyed first.

scholarly journals Crack Initiation, Propagation, and Failure Characteristics of Jointed Rock or Rock-Like Specimens: A Review

2019 ◽  
Vol 2019 ◽  
pp. 1-31 ◽  
Author(s):  
Ri-hong Cao ◽  
Ping Cao ◽  
Hang Lin ◽  
Xiang Fan ◽  
Chunyang Zhang ◽  
...  
Keyword(s):  
Rock Mass ◽  
Crack Initiation ◽  
Failure Modes ◽  
Failure Process ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Failure Behavior ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
Natural Rock

Rock masses are heterogeneous materials containing a large number of discontinuities, and the failure of the natural rock mass is induced by the crack propagation and coalescence of discontinuities, especially for the rock mass around tunnel or underground space. Because the deformation or failure process of jointed rock mass exhibits strongly nonlinear characteristics, it is also very difficult to predict the strength and failure modes of the rock mass. Therefore, it is very necessary to study the failure mechanisms of jointed rock mass under different stress conditions. Apart from the stress condition, the discontinuities geometry also has a significant influence on the mechanical behavior of jointed rock mass. Then, substantial, experimental, and numerical efforts have been devoted to the study of crack initiation, propagation, and coalescence of rock or rock-like specimens containing different kinds of joints or fissures. The purpose of this review is to discuss the development and the contribution of the experiment test and numerical simulation in failure behavior of jointed rock or rock-like specimens. Overall, this review can be classified into three parts. It begins by briefly explaining the significance of studying these topics. Afterwards, the experimental and numerical studies on the strength, deformation, and failure characteristics of jointed rock or rock-like materials are carried out and discussed.

scholarly journals A Study on Triaxial Unloading Test of Columnar-Jointed-Rock-Mass-Like Material with AW Velocity Analysis

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Jianrong Xu ◽  
Hao Li ◽  
Qingxiang Meng ◽  
Weiya Xu ◽  
Mingjie He ◽  
...  
Keyword(s):  
Rock Mass ◽  
Volume Expansion ◽  
Failure Modes ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Stress Strain ◽  
Deformation And Failure ◽  
Failure Patterns ◽  
Confining Pressures ◽  
Columnar Jointed Rock Mass

To study the strength, deformation, and failure patterns of columnar-jointed-rock-mass (CJRM) under unloading conditions, triaxial unloading tests using the CJRM-like material samples are carried out, and acoustic wave (AW) velocities are simultaneously recorded. Based on stress-strain curves and AW velocities under different initial confining pressures and unloading rates, the stress-strain characteristics, strength, and deformation parameters, failure modes, and variation of the AW velocity are analyzed. Test results show that the CJRM may exhibit intense volume expansion during the unloading process. With the increase of the unloading and its rate, the volume expansion becomes more serious and the failure mode becomes more complicated. By reducing the unloading (rate), a phenomenon of unloading relaxation is observed and the quality of CJRM is significantly improved. The AW velocity of CJRM shows a strong correlation with the volume strain, which verifies the effectiveness of applying AW velocity for assessing the rock quality. It is hoped that the research results may provide a reference for the construction and operation of the Baihetan Hydropower Project.

scholarly journals Study on the Failure Mechanism for Coal Roadway Stability in Jointed Rock Mass Due to the Excavation Unloading Effect

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2515 ◽  
Author(s):  
Eryu Wang ◽  
Guangbo Chen ◽  
Xiaojie Yang ◽  
Guofeng Zhang ◽  
Wenbin Guo
Keyword(s):  
Rock Mass ◽  
Numerical Model ◽  
Crack Propagation ◽  
Failure Mechanism ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Surrounding Rock ◽  
Coal Roadway ◽  
Roadway Stability ◽  
Rock Structure

Aiming at the large deformation instability problem caused by the excavation unloading of a coal roadway in deep-buried slowly inclined jointed rock mass, the geomechanical parameters and deformation failure characteristics of an engineering geomechanical model were investigated. The in-situ stress state of the model was measured with the stress relief method. The geological and mechanical properties of roadway surrounding rock were described. The surrounding rock structure was revealed with the electron microscopy scanning method, micro-fractures and randomly distributed joints highly developed in roadway surrounding rock. Field investigation and monitoring indicated the cross-section of roadway surrounding rock shrank continuously and the deformation distribution was obviously asymmetric. Shotcrete spalling and cable broken failures frequently occurred in the middle and ride side of roof and right rib. Based on the geomechanical conditions of the coal roadway, a discrete element numerical model of coal roadway in gently inclined jointed rock mass was established. The parameters of rock mass in the numerical model were calibrated. The model ran in unsupported condition to restore the evolution process of stress, crack propagation and deformation in roadway surrounding rock due to gradual deviatoric stress release caused by excavation. On this basis, the space-time evolution characteristics and law of stress, crack propagation and deformation were obtained and then the asymmetric large fragmentation and dilatation deformation failure mechanism of roadway surrounding rock in deep-buried slowly inclined jointed rock mass was revealed. The failure reasons of the support structure were analyzed, and the relevant support principles were proposed. The research results can provide scientific references for the stability control of roadways excavated in jointed rock mass.

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