Study on Rock Unloading Failure and its Effects on Rock Burst

2011 ◽  
Vol 71-78 ◽  
pp. 1455-1458 ◽  
Author(s):  
Li Ming Zhang ◽  
Zai Quan Wang
Keyword(s):  
Rock Burst ◽  
Failure Modes ◽  
Poisson Ratio ◽  
Deformation Modulus ◽  
Volumetric Strain ◽  
Lateral Strain ◽  
Mechanical Parameters ◽  
Tunnel Excavation ◽  
Failure Characteristics ◽  
Coulomb Criterion

The mechanical parameters and failure characteristics were obtained based on the results of triaxial unloading tests of limestone. Results show that: The evolution of volumetric strain is determined by lateral strain under unloading condition. Failure modes of rock can be classified into three types. Deformation modulus decreases and Poisson ratio increases in the process of unloading. Mohr-Coulomb criterion can not describe rock unloading failure strength property. Rock burst occur during tunnel excavation are closely related to the rock unloading failure characteristic.

Unloading Characteristics of Hard Rock at Depth

2011 ◽  
Vol 243-249 ◽  
pp. 2205-2210
Author(s):  
Ying Hui Lv ◽  
Xia Ting Feng ◽  
Jun Yan Liu
Keyword(s):  
Deformation Modulus ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Stress Path ◽  
Deep Excavation ◽  
Power Station ◽  
Failure Characteristics ◽  
Excavation Process ◽  
Rock Tunnels ◽  
Coulomb Criterion

DaGangShan power station in China is being excavation at 1500 meters deep below earth surface, where the surrounding rock is affected by high initial geo-stress. Deep excavation of rock tunnels causes release of high initial geo-stress and produces unloading action. As thus, a series of representative unloading tests on hard granite from DaGangShan power station are carried out to simulate dynamically excavation process, and in unloading tests, the stress path of decreasing confining pressure along with increasing axial pressure is accepted. The results of tests show as follows: (1) Under unloading condition, lateral deformation occurs in the unloading direction and volumetric strain changes from compression deformation to dilation deformation. (2) Under unloading condition, crack deformation appears, which results in Poisson’s ration rise and deformation modulus decrease. (3) Under unloading condition, hard granites behave brittle failure and Mogi-coulomb criterion can well describe the failure characteristics.

Mechanical Deformation Characteristics of Hard Rock in Deep Excavation

2011 ◽  
Vol 90-93 ◽  
pp. 61-66 ◽  
Author(s):  
Ying Hui Lv ◽  
Bin Yan
Keyword(s):  
Rock Mass ◽  
Simulation Analysis ◽  
Volumetric Strain ◽  
Mechanical Deformation ◽  
Deformation Characteristics ◽  
Deep Excavation ◽  
Tunnel Excavation ◽  
Failure Characteristics ◽  
Excavation Process ◽  
Coulomb Criterion

In the process of deep tunnel excavation, the surrounding rock mass, which often endures high initial geo-stress, is in the state of typical unloading. As the adjustment of stress induced by excavation, rock mass behaves a peculiar kind of mechanical deformation characteristics, different from those in loading conditions. As thus, a series of representative unloading tests on hard granite from DaGangShan power station in China, which is being excavation at 1500 meters deep below earth surface, are carried out to simulate dynamically excavation process for studying the peculiar mechanical deformation characteristics. On the basis of unloading tests, a series of research results are acquired as follows： (1) Under unloading condition, lateral deformation occurs in the unloading direction and volumetric strain changes from compression deformation to dilation deformation. (2) Under unloading condition, hard granites behave brittle failure and Mogi-coulomb criterion can well describe the failure characteristics. (3) According to curves of unloading tests, the constitutive model is deduced for simulation analysis.

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 Research on Failure Characteristics of Concrete Three-Point Bending Beams with Preexisting Cracks in Different Positions Based on Numerical Simulation

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Liuqun Zhao ◽  
Li Zheng ◽  
Hui Qin ◽  
Tiesuo Geng ◽  
Yonggang Tan ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Bearing Capacity ◽  
Failure Modes ◽  
Failure Process ◽  
Engineering Application ◽  
Tensile Failure ◽  
Engineering Structures ◽  
Failure Characteristics ◽  
Three Point Bending ◽  
Wide Range

Concrete three-point bending beams with preexisting cracks are widely used to study the growth process of I-II mixed mode cracks. Studying the failure characteristics of preexisting cracks at different locations on concrete three-point bending beams not only has important scientific significance but also has a wide range of engineering application backgrounds in the safety assessment of engineering structures. In this paper, through several numerical experiments, the influence of preexisting cracks at different positions on the failure characteristics of concrete three-point bending beams is studied, and three typical failure modes are obtained. The failure process of the specimens with three typical failure modes is discussed in detail, and it is pointed out that the crack failure mode is tensile failure. The change trends of bearing capacity, acoustic emission quantity, and acoustic emission energy of three typical failure modes are analyzed. The maximum bearing capacity, the maximum acoustic emission quantity, and energy of three failure modes of concrete three-point bending beams generally show an increasing trend.

scholarly journals The Meso-Analysis of the Rock-Burst Debris of Rock Similar Material Based on SEM

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Manqing Lin ◽  
Lan Zhang ◽  
Xiqi Liu ◽  
Yuanyou Xia ◽  
Jiaqi He ◽  
...  
Keyword(s):  
Rock Burst ◽  
Fractal Dimensions ◽  
Similar Material ◽  
Failure Characteristics ◽  
True Triaxial ◽  
Sem Image ◽  
Box Counting ◽  
Box Counting Dimension ◽  
Combined Test ◽  
Experimental Process

In order to explore the specimen failure characteristics during rock-burst under different gradient stress conditions, in this paper, a novel experimental technique was proposed; a common series of tests under two gradient stress paths were conducted on rock similar material specimens using the true-triaxial gradient and hydraulic-pneumatic combined test apparatus. And plaster was used as the rock similar material. In the experimental process, several rock-burst debris with area sizes of 100 mm2 were collected, and the fractal dimensions of typical detrital section crystal contours were analyzed and calculated using a scanning electron microscopy (SEM) method. The results showed that the specimens’ failure characteristics which had been induced by the two gradient stress processes were various. Also, the mesoscopic morphology of the rock-burst detrital section had effectively reflected its macroscopic failure characteristics. It was found that the fractal dimensions of the crystal contours of the specimen’s detrital section had fractal characteristics, and the box-counting dimension based on the SEM image could quantitatively describe the rock-burst failure characteristics. Furthermore, under the same magnification, the fractal dimensions of the crystal contours of the splitting failures were found to be relatively smaller than those of the shearing failures.

scholarly journals An Evaluation Method of Brittleness Characteristics of Shale Based on the Unloading Experiment

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1779 ◽  
Author(s):  
Xiaogui Zhou ◽  
Haiming Liu ◽  
Yintong Guo ◽  
Lei Wang ◽  
Zhenkun Hou ◽  
...  
Keyword(s):  
Evaluation Method ◽  
Shear Failure ◽  
Confining Pressure ◽  
Shear Zones ◽  
Loading Path ◽  
Mechanical Parameters ◽  
Failure Characteristics ◽  
Unloading Rate ◽  
Uplift And Erosion ◽  
Unloading Effect

Shale reservoir has an initial unloading effect during the natural uplift and erosion process, which causes the shale brittleness to change, affecting the design of the fracturing scheme. To consider this, the axial compression loading and confining pressure unloading experiment of shale is carried out, and then the influence of unloading rate on the mechanical parameters, failure characteristics, and the brittleness of rock are analyzed. What is more, a new evaluation method of brittleness characteristics that take the unloading effect into consideration is proposed. The conclusions are as follows: (1) The unloading rate has a weakening effect on the mechanical parameters, such as the destructive confining pressure and the residual strength of the samples. (2) The failure characteristics of shale specimens are a single shear failure in an oblique section under low unloading rate, and multiple shear zones accompanied with bedding fracture under high unloading rate. (3) The brittleness of shale samples is well verified by the brittleness index B d 1 and B d 2 during the loading path; nevertheless, it has shortage at the unloading path. This paper proposes a new brittleness evaluation method which can consider the influence of the different unloading rates and unloading points. Furthermore, there is a nice characterization between the brittleness damage and this method.

scholarly journals An Experimental and Numerical Study on the Flexural Performance of Over-Reinforced Concrete Beam Strengthening with Bolted-Compression Steel Plates: Part II

2019 ◽  
Vol 10 (1) ◽  
pp. 94 ◽  
Author(s):  
Shatha Alasadi ◽  
Zainah Ibrahim ◽  
Payam Shafigh ◽  
Ahad Javanmardi ◽  
Karim Nouri
Keyword(s):  
Failure Modes ◽  
Steel Plate ◽  
Numerical Study ◽  
Load Capacity ◽  
Plate Thickness ◽  
Steel Plates ◽  
Experimental Program ◽  
Failure Characteristics ◽  
Control Beam ◽  
Concrete Failure

This study presents an experimental investigation and finite element modelling (FEM) of the behavior of over-reinforced simply-supported beams developed under compression with a bolt-compression steel plate (BCSP) system. This study aims to avoid brittle failure in the compression zone by improving the strength, strain, and energy absorption (EA) of the over-reinforced beam. The experimental program consists of a control beam (CB) and three BCSP beams. With a fixed steel plate length of 1100 mm, the thicknesses of the steel plates vary at the top section. The adopted plate thicknesses were 6 mm, 10 mm, and 15 mm, denoted as BCSP-6, BCSP-10, and BCSP-15, respectively. The bolt arrangement was used to implement the bonding behavior between the concrete and the steel plate when casting. These plates were tested under flexural-static loading (four-point bending). The load-deflection and EA of the beams were determined experimentally. It was observed that the load capacity of the BCSP beams was improved by an increase in plate thickness. The increase in load capacity ranged from 73.7% to 149% of the load capacity of the control beam. The EA was improved up to about 247.5% in comparison with the control beam. There was also an improvement in the crack patterns and failure modes. It was concluded that the developed system has a great effect on the parameters studied. Moreover, the prediction of the concrete failure characteristics by the FE models, using the ABAQUS software package, was comparable with the values determined via the experimental procedures. Hence, the FE models were proven to accurately predict the concrete failure characteristics.

scholarly journals Numerical Analysis of the Anisotropy and Scale Effects on the Strength Characteristics of Defected Rockmass

2020 ◽  
Vol 2020 ◽  
pp. 1-21
Author(s):  
Xiabing Liu ◽  
Shaohui He ◽  
Dahai Wang
Keyword(s):  
Compression Test ◽  
Failure Modes ◽  
Scale Effects ◽  
Triaxial Compression ◽  
Influential Factor ◽  
Strength Characteristics ◽  
Uniaxial Compression Test ◽  
Mechanical Parameters ◽  
Strength Parameters ◽  
Strength Behavior

Discontinuous defect in the rockmass is a key influential factor in controlling the strength behavior, and how to estimate the anisotropic strength and scale effect on the defected rockmass is the remaining challenging focus in engineering application. In the present study, intact tuff samples cored from the Xiabeishan tunnel engineering in situ are conducted by experiment tests (i.e., uniaxial compression test, triaxial compression test, and Brazilian tensile test) to obtain the corresponding mechanical parameters. Results from the numerical simulations using the particle flow code (PFC) by the flat-jointed model (FJM) are performed to match the macroparameters from experimental results. It is observed that numerical results have good agreement with the macroscopic mechanical parameters of intact samples including UCS, BTS, triaxial compression strength, and corresponding deformation parameters. Finally, a series of uniaxial and confining compression tests are conducted by using a synthetic rockmass (SRM) method which is coupled with the discrete element method (DEM) and discrete fracture network (DFN). Then, the anisotropy and scale effects on the strength characteristics of the defected rockmass are investigated. The results show that defects have a vital effect on the failure mode and strength behavior of the rockmass in the research region. The strength parameters are changed with the specimen size. The REV size of the considered defected rockmass is regarded as 5 × 10 m, and this size is also influenced by the confinement level. The anisotropy of macroscopic strength parameters is found in the considered defected rockmass, whose stress-strain curves and failure modes are also discussed.

scholarly journals Study on the Stability of the Coal Seam Floor above a Confined Aquifer Using the Structural System Reliability Method

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Haifeng Lu ◽  
Xiuyu Liang ◽  
Nan Shan ◽  
You-Kuan Zhang
Keyword(s):  
Coal Seam ◽  
System Reliability ◽  
Failure Modes ◽  
Water Inrush ◽  
Series System ◽  
Mechanical Parameters ◽  
Structural System ◽  
Key Strata ◽  
Structural System Reliability ◽  
The Stability

A quantitative method of structural system reliability was proposed to study the influence of random rock mechanical parameters and loads on the stability of the coal seam floor above confined aquifers. To obtain the reliability probability of the floor, two modes of water-resistant floor failure were suggested as follows: (1) mining completely removed the water-resistant key strata of the floor. In this case, the failure modes were of three main types: mining failure, confined water intrusion, and combined mining failure and intrusion. (2) Failure modes included shear and tensile failures when the thickness of the key strata was greater than 0. On the basis of the elastic thin plate theory, the performance function that calculates the reliability probability of all modes could be obtained. The failure modes were regarded as the series system. The Monte Carlo method was employed to calculate the reliability probability of each failure mode and series system. The results showed that the random rock mechanical parameters and loads of the key strata significantly influence the antiwater inrush capacity of the floor. In addition, the water inrush coefficient and reliability probability can be simultaneously used as the evaluation indexes of water inrush risk. Both these indexes could improve the assessment of the reliability of the floor.

scholarly journals Stable anisotropic single-layer of ReTe2: a first principles prediction

2020 ◽  
Vol 44 (5) ◽  
pp. 450-457
Author(s):  
Mehmet YAĞMURCUKARDEŞ
Keyword(s):  
Raman Spectrum ◽  
Band Gap ◽  
First Principles ◽  
Anisotropic Material ◽  
Poisson Ratio ◽  
Single Layer ◽  
Mechanical Parameters ◽  
Lattice Orientation ◽  
Layer Form ◽  
Distorted Phase

In order to investigate the structural, vibrational, electronic, and mechanical features of single-layer ReTe2first-principles calculations are performed. Dynamical stability analyses reveal that single-layer ReTe2crystallize in adistorted phase while its 1H and 1T phases are dynamically unstable. Raman spectrum calculations show that single-layer distorted phase of ReTe2exhibits 18 Raman peaks similar to those of ReS2and ReSe2. Electronically, single-layerReTe2is shown to be an indirect gap semiconductor with a suitable band gap for optoelectronic applications. In addition,it is found that the formation of Re-units in the crystal induces anisotropic mechanical parameters. The in-plane stiffnessand Poisson ratio are shown to be significantly dependent on the lattice orientation. Our findings indicate that single-layer form of ReTe2can only crystallize in a dynamically stable distorted phase formed by the Re-units. Single-layer ofdistorted ReTe2can be a potential in-plane anisotropic material for various nanotechnology applications.

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