Effect of Cyclic Wetting–Drying Treatment on Strength and Failure Behavior of Two Quartz-Rich Sandstones Under Direct Shear

Evidence indicate that the stability of rock mass is highly associated with the shear behaviours of jointed surfaces under the effect of in situ stress conditions. Understanding the shear failure mechanism of jointed surface has great significance for tunneling and drilling engineering. Direct shear tests were conducted on jointed rock-like specimens to investigate the influence of joint roughness and normal stress on shear failure characteristics. In the present study, regular triangular sawtooth was produced to simulate different asperities. Based on the direct shear test, the specimens exhibited four types of failure modes: damage tend to occur on the sawtooth tips under low normal stress; whereas damage occurred on a large scale under high normal stress; a localized region of the sawtooth was worn when the dilation angle was small; meanwhile the sawtooth tips or base were cut off when the dilation angle was large. In addition, Acoustic Emission (AE) technology was adopted to synchronously monitor the development of cracks during testing. Further attempt has been carried out to simulate the crack initiation, propagation and coalescence using Particle Flow Code (PFC). The numerical model has successfully verified and explained the crack behaviors determined by the shear failure mechanism in the physical test. Additionally, the irregular profile was introduced in the PFC, it was found that the failure behavior in sawtooth profile has established a good conclusion to fully understand the failure mechanism in the irregular profile. This work can provide some reference for evaluating the behavior of underground engineering composed of jointed rock masses during the shearing.

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Experimental and Numerical Study of the Failure Behavior of Intermittent Rock Joints Subjected to Direct Shear Load

Advances in Civil Engineering ◽

10.1155/2018/4294501 ◽

2018 ◽

Vol 2018 ◽

pp. 1-19 ◽

Cited By ~ 10

Author(s):

Xiang Fan ◽

Kaihui Li ◽

Hongpeng Lai ◽

Qihua Zhao ◽

Zhenhua Sun

Keyword(s):

Crack Initiation ◽

Rock Joints ◽

Failure Behavior ◽

Second Phase ◽

Direct Shear ◽

Crack Initiation Stress ◽

Secondary Cracks ◽

Peak Shear Stress ◽

Initiation Stress ◽

Three Phases

Two series of intermittent rock joints containing three joints arranged along the central shear axis were considered in this study. The failure behavior under direct shear loads was investigated by means of both physical tests and numerical simulations. The cracking behavior was found to be distinctly associated with the joint arrangement. Several types of main and secondary cracks were identified. The variation trends of the crack initiation stress ratio with inclination angle were analyzed and found to be partly different for the two series of intermittent joints. The whole fracturing process was characterized by three phases. Not all samples have to experience all three phases. The second phase is alternative and can be reflected by the shearing curve. Hence, two types of shearing curves, including single and double peaks, were identified. The double peak is due to the extrusion or sawteeth cutting in the second phase. Moreover, the numerical micromechanical analysis was performed to explain the shear behavior using the contact force and microcrack within the specimen. Based on the numerically measured local stresses, maximum and minimum principal stresses around the middle joint at crack initiation stress and peak shear stress were analyzed.

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GRAPHS FOR THE DIRECT SHEAR DESIGN OF PRESTRESSED CONCRETE MEMBERS

PCI Journal ◽

10.15554/pcij.08011969.14.29 ◽

1969 ◽

Vol 14 (4) ◽

pp. 14-29

Author(s):

Francis J. Francis J. Jacques

Keyword(s):

Prestressed Concrete ◽

Direct Shear ◽

Concrete Members ◽

Shear Design

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Direct shear strength test on rocks along discontinuities, under laboratory conditions

Pollack Periodica ◽

10.1556/pollack.9.2014.3.15 ◽

2014 ◽

Vol 9 (3) ◽

pp. 139-150 ◽

Cited By ~ 5

Author(s):

Ildikó Buocz ◽

Nikoletta Rozgonyi-Boissinot ◽

Ákos Török ◽

Péter Görög

Keyword(s):

Shear Strength ◽

Strength Test ◽

Direct Shear ◽

Shear Strength Test ◽

Laboratory Conditions

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Failure Behavior and Mechanisms in Dense Highly Aligned Brittle Nanowire Structures

10.26226/morressier.5f5f8e69aa777f8ba5bd5f7a ◽

2020 ◽

Author(s):

Rebecca Anne Gallivan

Keyword(s):

Failure Behavior

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Interpreting Laser-Based Fault Localization Results: Case Studies

ISTFA 2019: Conference Proceedings from the 45th International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa2019p0168 ◽

2019 ◽

Author(s):

Sukho Lee ◽

John van den Biggelaar ◽

Marc van Veenhuizen

Keyword(s):

Case Studies ◽

Circuit Design ◽

High Sensitivity ◽

Failure Behavior ◽

Process Technology ◽

Resistance Change ◽

Voltage Imaging ◽

Root Cause ◽

First Case ◽

Proper Interpretation

Abstract Laser-based dynamic analysis has become a very important tool for analyzing advanced process technology and complex circuit design. Thus, many good reference papers discuss high resolution, high sensitivity, and useful applications. However, proper interpretation of the measurement is important as well to understand the failure behavior and find the root cause. This paper demonstrates this importance by describing two insightful case studies with unique observations from laser voltage imaging/laser voltage probing (LVP), optical beam induced resistance change, and soft defect localization (SDL) analysis, which required an in-depth interpretation of the failure analysis (FA) results. The first case is a sawtooth LVP signal induced by a metal short. The second case, a mismatched result between an LVP and SDL analysis, is a good case of unusual LVP data induced by a very sensitive response to laser light. The two cases provide a good reference on how to properly explain FA results.

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