scholarly journals Experimental Study of the Mechanical Characteristics of a Rock-Like Material Containing a Preexisting Fissure under Loading and Unloading Triaxial Compression

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Taoli Xiao ◽  
Mei Huang ◽  
Min Gao
Keyword(s):  
Experimental Study ◽  
Failure Mode ◽  
Mechanical Characteristics ◽  
Failure Modes ◽  
Shear Failure ◽  
Triaxial Compression ◽  
Tensile Failure ◽  
Underground Engineering ◽  
Inclination Angles ◽  
Loading And Unloading

An experimental study of a rock-like material containing a preexisting fissure subjected to loading and unloading triaxial compression is carried out, and the results show that the mechanical characteristics of the rock-like specimen depend heavily on the loading paths and the inclination of the fissure. The triaxial loading experiment results show that the failure strength linearly increases, while the residual strength linearly decreases with increasing inclination. Furthermore, specimens subjected to triaxial compression show an “X”-type shear failure mode. The triaxial unloading compression experimental results show that specimens with different inclination angles have various failure modes. Specimens with gentle inclinations show a tensile-shear mix failure mode, specimens with middle inclinations show a shear-sliding failure mode, and specimens with steep inclinations show a tensile failure mode. These findings can be used to forecast excavation-induced instabilities in deep underground engineering rock structures.

scholarly journals Cracking Behaviors and Mechanical Properties of Rock-Like Specimens with Two Unparallel Flaws under Conventional Triaxial Compression

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Huilin Le ◽  
Shaorui Sun ◽  
Chenghua Xu ◽  
Liuyang Li ◽  
Yong Liu
Keyword(s):  
Mechanical Properties ◽  
Inclination Angle ◽  
Failure Modes ◽  
Shear Failure ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Critical Value ◽  
Tensile Failure ◽  
Rock Bridge ◽  
Bridge Length

Flaws existing in rock masses are generally unparallel and under three-dimensional stress; however, the mechanical and cracking behaviors of the specimens with two unparallel flaws under triaxial compression have been rarely studied. Therefore, this study conducted comprehensive research on the cracking and coalescence behavior and mechanical properties of specimens with two unparallel flaws under triaxial compression. Triaxial compressive tests were conducted under different confining pressures on rock-like specimens with two preexisting flaws but varying flaw geometries (with respect to the inclination angle of the two unparallel flaws, rock bridge length, and rock bridge inclination angle). Six crack types and eleven coalescence types in the bridge region were observed, and three types of failure modes (tensile failure, shear failure, and tensile-shear failure) were observed in experiments. Test results show that bridge length and bridge inclination angle have an effect on the coalescence pattern, but the influence of bridge inclination angle is larger than that of the bridge length. When the confining pressure is low, coalescence patterns and failure modes of the specimens are greatly affected by flaw geometry, but when confining pressure rose to a certain level, the influence of confining pressure is larger than the effect of flaw geometry. The peak strength of the specimens is affected by flaw geometry and confining pressure. There is a critical value for the bridge length. If the bridge length is larger than the critical value, peak strengths of the samples almost keep constant as the bridge length increases. In addition, as the bridge inclination angle increases, there is an increase in the probability of tensile cracks occurring, and with an increase in the confining pressure, the probability of the occurrence of shear cracks increases.

scholarly journals Particle Flow Simulation of the Strength and Failure Characteristics of a Layered Composite Rock-Like Sample with a Single Hole

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1132
Author(s):  
Guozhu Wang ◽  
Yu Wang ◽  
Lei Song ◽  
Hao Shi ◽  
Mingwei Zhang ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Failure Mode ◽  
Failure Modes ◽  
Shear Failure ◽  
Surrounding Rock ◽  
Tensile Failure ◽  
Practical Significance ◽  
Rock Masses ◽  
Engineering Structures ◽  
Layered Rock

Layered rock masses with holes are common in nature. Their mechanical behavior plays an important role in the safety and stability of engineering structures. However, previous studies have concentrated on a single lithological layer, and few studies have reported on the mechanical behavior of layered rock masses with holes. Based on the concept of symmetry, uniaxial compression tests and numerical simulations were performed on rock-like specimens with three layers and a hole in the interlayer. The hole was in the center of the sample and was symmetrical up and down. The influence of the thickness and strength of the interlayer on the mechanical behavior and failure processes of the layered rock masses with holes was investigated. The results show that the peak strength and elastic modulus were associated with the thickness and strength of the interlayer. Three failure modes were observed in the specimens, which were not only related to the thickness and strength of the interlayer, but also affected by the presence of the hole. When the thickness of the interlayer is small, mainly a single failure mode was observed (tensile failure or shear failure). However, when the interlayer was thick, the failure mode was tension-shear mixed failure. The failure mechanism of the specimens was primarily crack propagation at the edge of the hole. These research results can provide a basis for site selection, and the design of surrounding rock protection and support parameters, and thus have important practical significance for improving surrounding rock stability and ensuring construction safety.

scholarly journals Experimental Study on the Mechanical Properties and Seepage Characteristics of Red Sandstone with a Single Persistent Joint under Triaxial Compression

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Wei Wang ◽  
Shifan Liu ◽  
Chong Shi ◽  
Shanxi Zheng ◽  
Qizhi Zhu
Keyword(s):  
Mechanical Properties ◽  
Pore Pressure ◽  
Failure Modes ◽  
Shear Failure ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Strengthening Effect ◽  
Red Sandstone ◽  
Inclination Angles ◽  
Seepage Characteristics

In this research, the conventional triaxial compression experiments for intact red sandstone specimens and the specimens with a single persistent joint at different inclination angles, i.e., 0°, 30°, 45°, and 90°, were conducted at first. Based on the results of the conventional tests, the effects of the confining pressure and the joint inclination angle on the mechanical properties including deformation behavior and strength parameters were summarized and analyzed, respectively. We find that the strength and deformation of jointed red sandstone are enlarged due to the increment of confining pressure, and the mechanical parameters of specimens show a U-shaped development with the rise of the joint angle. Besides, to investigate the effects of the pore pressure on seepage characteristics of rocks with joint angles at 0°, 45°, and 90°, a series of triaxial compression drainage tests on the jointed red sandstone were performed. The results show that the pore pressure has a weakening effect on the strength of jointed specimens, which can reduce the strengthening effect induced by confining pressure. Meanwhile, the tested specimens mostly present shear failure modes. As a result, the mechanical responses, seepage characteristics, and cracking modes in red sandstone containing a single persistent joint under triaxial compression are revealed.

scholarly journals Experimental Investigation on the Mechanical Characteristics and Deformation Behaviour of Fractured Rock-Like Material with One Single Fissure under the Conventional Triaxial Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Taoli Xiao ◽  
Mei Huang ◽  
Cheng Cheng ◽  
Yunlong He
Keyword(s):  
Mechanical Characteristics ◽  
Failure Modes ◽  
Shear Failure ◽  
Early Stage ◽  
Fractured Rock ◽  
Deformation Behaviour ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Confining Pressure ◽  
Material Specimen

An experimental study was carried out on a rock-like material specimen containing a single fissure to investigate its mechanical characteristics and deformation behaviour under triaxial compression. The mechanical characteristics, such as peak strength and residual strength, are discussed. The confining pressure had a distinct effect on the ductility characteristics of the specimen. “A distinct stress drop” occurred in the early stage of the stress-strain curve when the length fissure was relatively long. The I-crack, II-crack, and III-crack are all observed under triaxial compression, and the III-crack is commonly observed under triaxial compression. Confining pressure plays an essential role in affecting the failure mode of the specimen. There are three kinds of failure modes in the triaxial compression experiment on a rock-like material specimen with one single fissure: tensile-shear comprehensive failure, “X”-shaped shear failure, and shear failure along the fissure plane. These results are important and fundamental to understand the fracture mechanism of rock engineering.

scholarly journals An Analytical Model for Fracture Initiation of Radial Drilling-Fracturing in Shale Formations

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 1) ◽  
Author(s):  
Yuxin Chen ◽  
Yunhong Ding ◽  
Chong Liang ◽  
Yu Bai ◽  
Dawei Zhu ◽  
...  
Keyword(s):  
Failure Mode ◽  
Failure Modes ◽  
Shear Failure ◽  
Fracture Initiation ◽  
In Situ Stress ◽  
Tensile Failure ◽  
Shale Formations ◽  
Biot Coefficient ◽  
Radial Drilling

Abstract Radial drilling-fracturing, the combination of radial drilling and hydraulic fracturing, can guide fractures toward the target area and effectively enhance the recovery of the low permeable reservoir. In this paper, based on the stress superposition principle, we establish an analytical model to predict fracture initiation pressure (FIP) and the shale failure mode for radial drilling-fracturing applied in shale formations. In contrast with the former studies, this model can additionally consider the failure from shale beddings and is more applicable in the shale reservoir. The model classifies the shale failure into three modes and, respectively, gives the criterion for each failure mode. Then, a series of sensitivity analyses is conducted by examining effects of various parameters. By analyzing the variation characteristic of the initiation pressures required for three failure modes, the main conclusions are as follows. Firstly, matrix failure and shear failure along bedding tend to take place when the azimuth of radial borehole is moderate. Small and large azimuths are favorable for the occurrence of tensile failure along bedding. Secondly, a high ratio of horizontal in situ stress predisposes shale to generate matrix failure, and bedding tensile failure and bedding shear failure are apt to occur when the ratio of horizontal in situ stress is low. Thirdly, with the increasing intersection angle of the radial borehole wall and bedding plane, the failure mode apt to occur changes from bedding tensile failure to bedding shear failure and then to matrix failure. Fourthly, shale prefers to yield bedding shear failure under a small Biot coefficient and generate the other two failure modes when Biot coefficient is large. Fifthly, permeability coefficient virtually has no influence on the failure mode of shale. The research clarifies the fracture initiation characteristics of radial drilling-fracturing in shale formations and provides a reference for the field application of radial drilling-fracturing.

Machine learning-based failure mode identification of RCSPSW

2021 ◽  
Author(s):  
Dongqi Jiang ◽  
Shanquan Liu ◽  
Tao Chen ◽  
Gang Bi
Keyword(s):  
Machine Learning ◽  
Failure Mode ◽  
Failure Modes ◽  
Shear Failure ◽  
Tall Buildings ◽  
Shear Walls ◽  
Superior Performance ◽  
Ann Model ◽  
Mode Recognition ◽  
Wide Range

<p>Reinforced concrete – steel plate composite shear walls (RCSPSW) have attracted great interests in the construction of tall buildings. From the perspective of life-cycle maintenance, the failure mode recognition is critical in determining the post-earthquake recovery strategies. This paper presents a comprehensive study on a wide range of existing experimental tests and develops a unique library of 17 parameters that affects RCSPSW’s failure modes. A total of 127 specimens are compiled and three types of failure modes are considered: flexure, shear and flexure-shear failure modes. Various machine learning (ML) techniques such as decision trees, random forests (RF), <i>K</i>-nearest neighbours and artificial neural network (ANN) are adopted to identify the failure mode of RCSPSW. RF and ANN algorithm show superior performance as compared to other ML approaches. In Particular, ANN model with one hidden layer and 10 neurons is sufficient for failure mode recognition of RCSPSW.</p>

Study on Failure of Rock Mass around Deep Tunnel

2011 ◽  
Vol 99-100 ◽  
pp. 370-374 ◽  
Author(s):  
Yue Hong Qian ◽  
Ting Ting Cheng ◽  
Xiang Ming Cao ◽  
Chun Ming Song
Keyword(s):  
Rock Mass ◽  
Stress Field ◽  
Failure Modes ◽  
Shear Failure ◽  
Simple Function ◽  
Tensile Failure ◽  
Deep Tunnel ◽  
Main Mode

During excavating the problem of unloading is a dynamic one essentially. Assuming the unloading ruled by a simple function and based on the Hamilton principal, the distribution of the stress field nearby the tunnel is obtained. The characteristics of the failure nearby the tunnel are analyzed considering the shear failure and tensile failure. The results show that the main mode of the shear failure, intact and tensile failure occurs from the tunnel. The characteristic of the shear failure, intact and tensile failure are one of the likely failure modes.

scholarly journals Failure Characteristics and Mechanism of Multiface Slopes under Earthquake Load Based on PFC Method

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Tao Yang ◽  
Yunkang Rao ◽  
Huailin Chen ◽  
Bing Yang ◽  
Jiangrong Hou ◽  
...  
Keyword(s):  
Moisture Content ◽  
Failure Mechanism ◽  
Failure Modes ◽  
Shear Failure ◽  
Shaking Table ◽  
Tensile Failure ◽  
Particle Flow Code ◽  
Shear Cracks ◽  
Local Shear ◽  
Shear Slip

Understanding the failure mechanism and failure modes of multiface slopes in the Wenchuan earthquake can provide a scientific guideline for the slope seismic design. In this paper, the two-dimensional particle flow code (PFC2D) and shaking table tests are used to study the failure mechanism of multiface slopes. The results show that the failure modes of slopes with different moisture content are different under seismic loads. The failure modes of slopes with the moisture content of 5%, 8%, and 12% are shattering-shallow slip, tension-shear slip, and shattering-collapse slip, respectively. The failure mechanism of slopes with different water content is different. In the initial stage of vibration, the slope with 5% moisture content produces tensile cracks on the upper surface of the slope; local shear slip occurs at the foot of the slope and develops rapidly; however, a tensile failure finally occurs. In the slope with 8% moisture content, local shear cracks first develop and then are connected into the slip plane, leading to the formation of the unstable slope. A fracture network first forms in the slope with 12% moisture content under the shear action; uneven dislocation then occurs in the slope during vibration; the whole instability failure finally occurs. In the case of low moisture content, the tensile crack plays a leading role in the failure of the slope. But the influence of shear failure becomes greater with the increase of the moisture content.

Failure analysis of three-dimensional braided composite tubes under torsional load: Experimental study

2017 ◽  
Vol 36 (12) ◽  
pp. 878-888 ◽  
Author(s):  
Xiaopei Wang ◽  
Deng’an Cai ◽  
Chao Li ◽  
Fangzhou Lu ◽  
Yu Wang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Failure Modes ◽  
Shear Failure ◽  
Three Dimensional ◽  
Damage Mechanism ◽  
Test Device ◽  
Composite Tubes ◽  
Torsional Strength ◽  
Braided Composite ◽  
Torsional Load

An experimental study on the effects of braided processes on the torsional strength, torsional modulus and failure modes of the three-dimensional braided composite tubes are presented. Based on the movement of carries, the yarn traces of three-dimensional braided composite tubes are analyzed systematically. Four different three-dimensional braided composite tubes are formed by resin transfer molding, and a number of torsional tests are performed respectively using a special test device. It is found that the torsional strength of three-dimensional five-directional braided composite tubes is higher than others, while the torsional modulus of three-dimensional multi-layer wrapping braided composite tubes is the highest. Furthermore, the damage behaviors of 3D braided composite tubes are significantly influenced by braiding process. One focus is to evaluate the damage mechanism of three-dimensional braided composite tubes by cutting the specimens and using scanning electron microscopy. Under torsional load, three-dimensional five-directional braided composite tubes and three-dimensional surface-core five-directional braided composite tubes are fractured in compression and shear failure, while three-dimensional multi-layer wrapping braided composite tubes and three-dimensional seven-directional braided composite tubes are split open in tensile and shear failure.

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