scholarly journals An Index for Estimating the Stability of the Layered Rock Masses under Excavation Disturbance

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Ding-ping Xu ◽  
Gong-kai Gu ◽  
Liang-peng Wan ◽  
Dong-fang Chen ◽  
Shu-ling Huang
Keyword(s):  
Rock Mass ◽  
Safety Factor ◽  
Rock Masses ◽  
Deformation And Failure ◽  
Layered Rock ◽  
Bedding Planes ◽  
Reinforcement Measure ◽  
Tunnel Section ◽  
Layered Rock Mass ◽  
The Stability

The mechanical behaviours of layered rock mass exhibit significant differences in the directions parallel and vertical to the bedding planes. The deformation and failure of a layered rock mass has remarkable weak-plane dependence, which brings a major challenge to the control of the stability of the surrounding rock mass in underground openings. In this study, a layered rock mass is firstly regarded as a composite material composed of interlayered rocks and bedding planes. Then, based on the Mohr–Coulomb and maximum tensile stress criteria, an index of point safety factor for a layered rock mass is established considering the mechanical properties of interlayered rocks and bedding planes. The safety of the artificial layered rock mass specimens in the triaxial test is evaluated using this index. The results show that the distribution of this index is in good agreement with the macroscopic failed zone of the rock specimen, indicating that this index is feasible for characterizing the macroscopic failure of rock masses. Finally, the index is adopted to evaluate the stability of the midpartition between the #3 and #4 diversion tunnels at the right bank of the Wudongde hydropower station before and after its reinforcement. The results indicate that there is a yielded zone where the point safety factor is less than 1.0 in the unreinforced midpartition of the collapsed tunnel section, and it is nearly connected. If it is not reinforced in time, collapse cut-through of the entire midpartition may occur and then endanger the overall stability of the tunnel. After the emergency reinforcement measure with two-ended anchored piles and concrete backfill, the safety of the midpartition is significantly improved. In this case, the safety factor is much larger than 1.0, indicating that the adoption of this emergency reinforcement measure is effective.

scholarly journals Research on the Layered Rock Mass Excavation Relaxation Stability of Underground Caverns

2020 ◽  
Vol 165 ◽  
pp. 03024
Author(s):  
Ying Zhang ◽  
Heng Zhou ◽  
Shengjie Di ◽  
Xi Lu
Keyword(s):  
Rock Mass ◽  
Mechanical Characteristics ◽  
Generation System ◽  
Yield Zone ◽  
Layered Rock ◽  
Underground Caverns ◽  
Structure Surface ◽  
Layered Rock Mass ◽  
Power Generation System ◽  
The Stability

In order to compare the influence of rock mass parameters weakening on the deformation and stability of excavation caverns in layered rock mass, based on power generation system caverns of a hydropower station, the stability and deformation of the caverns is analyzed. The results show that the mechanical characteristics of the structure surface play a major role in controlling the stability of caverns. And the displacement and yield zone value of plan 3, which adopt elastic-plastic softening model, are significantly larger than other two. The method which consider the residual strength of structure surface is more suitable for the excavation calculation of layered rock mass cavern.

scholarly journals Space-Time Distribution Laws of Tunnel Excavation Damaged Zones (EDZs) in Deep Mines and EDZ Prediction Modeling by Random Forest Regression

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Qiang Xie ◽  
Kang Peng
Keyword(s):  
Rock Mass ◽  
Random Forest ◽  
Time Distribution ◽  
Space Time ◽  
Surrounding Rock ◽  
Layered Rock ◽  
Blasting Excavation ◽  
Layered Rock Mass ◽  
Distribution Laws ◽  
The Stability

The formation process of EDZs (excavation damaged zones) in the roadways of deep underground mines is complex, and this process is affected by blasting disturbances, engineering excavation unloading, and adjustment of field stress. The range of an excavation damaged zone (EDZ) changes as the time and space change. These changes bring more difficulties in analyzing the stability of the surrounding rock in deep engineering and determining a reasonable support scheme. In a layered rock mass, the distribution of EDZs is more difficult to identify. In this study, an ultrasonic velocity detector in the surrounding rock was used to monitor the range of EDZs in a deep roadway which was buried in a layered rock mass with a dip angle of 20–30°. The space-time distribution laws of the range of EDZs during the excavation process of the roadway were analyzed. The monitoring results showed that the formation of an EDZ can be divided into the following stages: (1) the EDZ forms immediately after the roadway excavation, which accounts for approximately 82%–95% of all EDZs. The main factors that affect the EDZ are the blasting load, the excavation unloading, and the stress adjustment; (2) as the roadway excavation continues, the range of the EDZs increases because of the blasting excavation and stress adjustment; (3) the later excavation zone has a comparatively larger EDZ value; and (4) an asymmetric supporting technology is necessary to ensure the stability of roadways buried in layered rocks. Additionally, the predictive capability of random forest modeling is evaluated for estimating the EDZ. The root-mean-square error (RMSE) and mean absolute error (MAE) are used as reliable indicators to validate the model. The results indicate that the random forest model has good prediction capability (RMSE = 0.1613 and MAE = 0.1402).

Research on Shear Failure Criterion for Layered Rock Mass

2012 ◽  
Vol 446-449 ◽  
pp. 1491-1496 ◽  
Author(s):  
Zhi Zeng Zhang ◽  
Lan Lan Zhou ◽  
Zhen Xia Yuan ◽  
Zhong Hua Sun
Keyword(s):  
Rock Mass ◽  
Failure Criterion ◽  
Shear Failure ◽  
Three Dimensional ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Layered Rock ◽  
Layered Rock Mass ◽  
The Stability ◽  
Confining Pressure Effect

In order to study the stability of layered rock mass, a shear failure criterion for layered rock mass is presented and its program is compiled in C language. The shear failure criterion consists of two parts: firstly, four empirical expressions are suggested in which shear strength parameters vary with the direction; secondly, a pilot calculation method is developed to judge whether a shear failure plane in layered rock mass occurs or not and give its occurrence under three dimensional stress condition. A triaxial numerical experiment on layered rock mass is designed to test the shear failure criterion, and its results reflect the characters including obliquity effect, confining pressure effect and failure mode which conform to the previous triaxial tests.

Model Test Study on Influences of Layered Rock Mass Dip Angle on Stability of Deep-Buried Tunnel

2011 ◽  
Vol 90-93 ◽  
pp. 2363-2371
Author(s):  
Bin Wei Xia ◽  
Ke Hu ◽  
Yi Yu Lu ◽  
Dan Li ◽  
Zu Yong Zhou
Keyword(s):  
Rock Mass ◽  
Physical Model ◽  
Model Test ◽  
Physical Models ◽  
Physical Model Test ◽  
Stress Distributions ◽  
Failure Characteristics ◽  
Layered Rock ◽  
Layered Rock Mass ◽  
Dip Angle

Physical models of layered rock mass with different dip angles are built by physical model test in accordance with the bias failure characteristics of surrounding rocks of layered rock mass in Gonghe Tunnel. Bias failure characteristics of surrounding rocks in thin-layered rock mass and influences of layered rock mass dip angle on stability of tunnel are studied. The research results show that failure characteristics of physical models generally coincide with those of surrounding rocks monitored from the tunnel site. The failure regions of surrounding rock perpendicular to the stratification planes are obviously larger than those parallel to. The stress distributions and failure characteristics in the surrounding rocks are similar to each physical model of different dip angles. The stress distributions and failure regions are all elliptic in shape, in which the major axis is in the direction perpendicular to the stratification planes while the minor axis is parallel to them. As a result, obvious bias failure of surrounding rocks has gradually formed. The physical model tests provide reliable basis for theoretical analysis on the failure mechanism of deep-buried layered rock mass.

scholarly journals Key Factors Affecting the Deformation and Failure of Surrounding Rock Masses in Large-Scale Underground Powerhouses

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Meng Wang ◽  
Jia-wen Zhou ◽  
An-chi Shi ◽  
Jin-qi Han ◽  
Hai-bo Li
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Surrounding Rock ◽  
Rock Masses ◽  
Affecting Factors ◽  
Key Factors ◽  
Underground Powerhouse ◽  
Deformation And Failure ◽  
Factors Affecting ◽  
Geological Conditions

The stability of the surrounding rock masses of underground powerhouses is always emphasized during the construction period. With the general trends toward large-scale, complex geological conditions and the rapid construction progress of underground powerhouses, deformation and failure issues of the surrounding rock mass can emerge, putting the safety of construction and operation in jeopardy and causing enormous economic loss. To solve these problems, an understanding of the origins and key affecting factors is required. Based on domestic large-scale underground powerhouse cases in the past two decades, key factors affecting the deformation and failure of the surrounding rock mass are summarized in this paper. Among these factors, the two most fundamental factors are the rock mass properties and in situ stress, which impart tremendous impacts on surrounding rock mass stability in a number of cases. Excavation is a prerequisite of surrounding rock mass failure and support that is classified as part of the construction process and plays a pivotal role in preventing and arresting deformation and failure. Additionally, the layout and structure of the powerhouse are consequential. The interrelation and interaction of these factors are discussed at the end of this paper. The results can hopefully advance the understanding of the deformation and failure of surrounding rock masses and provide a reference for design and construction with respect to hydroelectric underground powerhouses.

Constitutive model and elastic parameters for layered rock mass based on combined Hooke spring

2018 ◽  
Vol 10 (3-4) ◽  
pp. 145-156
Author(s):  
Zhang Ligang ◽  
Qu Guangqiu ◽  
Qu Sining ◽  
Liu Zhaoyi
Keyword(s):  
Rock Mass ◽  
Constitutive Model ◽  
Elastic Parameters ◽  
Layered Rock ◽  
Layered Rock Mass

Feasibility of analytical determination of the stress field in a layered rock mass

1990 ◽  
Vol 26 (2) ◽  
pp. 117-122
Author(s):  
E. V. Goncharov ◽  
A. A. Pimenov
Keyword(s):  
Rock Mass ◽  
Stress Field ◽  
Analytical Determination ◽  
Layered Rock ◽  
Layered Rock Mass

scholarly journals Mechanical Characteristics and Failure Modes of Low-Strength Rock Samples with Dissimilar Fissure Dip Angles

2021 ◽  
Author(s):  
Y L Wang ◽  
D S Liu ◽  
K Li ◽  
X M Hu ◽  
D Chen
Keyword(s):  
Rock Mass ◽  
Mechanical Characteristics ◽  
Failure Modes ◽  
High Strength ◽  
Rock Masses ◽  
Deformation And Failure ◽  
Deformation Features ◽  
Low Strength ◽  
Dip Angle ◽  
Strength Rock

The mechanical characteristics and failure modes of low-strength rock sample with various fissure dip angles were investigated by conventional uniaxial compression test and three-dimensional (3D) crack reconstruction. The results indicated that compared with high-strength rock masses, cracks had different influences on the low-strength rock mass mechanical deformation features. Thereinto, the dip angle of fissures can cause post-peak failure stage of stress-strain curve change from swift decline to multi-step down, showing obvious ductility deformation and failure characteristics. Peak strength and elastic modulus owned an anti-S-shaped growth tendency with the growth of fissure dip angle, which was positively correlated and greatest subtle to the fissure dip angle α < 21° and α > 66.5°. The axial peak strain reduced first and enlarged rapidly with growing fissure dip angle, suggesting a V-shaped change trend. Increasing the fissure dip angle will change the sample failure mode, experienced complete tensile failure to tensile-shear composite failure, and ultimately to typical shear failure. Also, the crack start angle decreased with enlarging fissure dip angle, larger than that the high-strength rock mass fissure dip angle. The above research findings can complement and improve the study of fissured rock masses.

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