Application of acoustic emission for monitoring shear behavior of bonded concrete–rock joints under direct shear test

2012 ◽  
Vol 39 (8) ◽  
pp. 887-896 ◽  
Author(s):  
Z.A. Moradian ◽  
G. Ballivy ◽  
P. Rivard
Keyword(s):  
Acoustic Emission ◽  
Shear Strength ◽  
Normal Load ◽  
Adhesive Bond ◽  
Shear Behavior ◽  
Displacement Rate ◽  
Bond Breaking ◽  
Bonded Joints ◽  
Direct Shear ◽  
Shear Process

Studying shear behavior and failure mechanism of concrete–rock interfaces between concrete structures and rock mass is highly important. To this end, laboratory direct shear tests were conducted on several bonded interfaces. The effect of normal stress, displacement rate, and bonding percentage on shear behavior of bonded joints were also evaluated. The results showed that the adhesive bond between concrete and rock has the most important effect on shear mechanism of concrete–rock interfaces. When the normal load is low, the asperities do not contribute in shear process, so the shear strength of the joints is governed by adhesive bond. The only contribution of the asperities is that they show a small peak after bond breaking peak. When the normal load is high, the asperities break simultaneously with adhesive bond and they show their contribution in the whole shear process. In a constant normal load, by decreasing bonding percentage, the brittle failure of the bonded joints is changed into softening failure because of less contribution of the adhesive bond and more contribution of the rough asperities in joint failure. Acoustic emission (AE) monitoring of bonded joints showed that for all different tested samples under various loading conditions, there has been no or very few AE activities before adhesive bond breaking point, indicating that other parameters (roughness, normal load, displacement rate) are impressed by adhesive bond and maximum shear strength is determined by this parameter.

scholarly journals Characteristics of Direct Shear and Particle Breakage of Pebble Gravel Materials

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Chenjie Hong ◽  
Man Huang ◽  
Danyu Zhang ◽  
Pingshan Shou ◽  
Zhiyong Zhu
Keyword(s):  
Particle Size ◽  
Shear Strength ◽  
Large Scale ◽  
Size Range ◽  
Normal Load ◽  
Particle Breakage ◽  
Direct Shear ◽  
Particle Size Range ◽  
Relationship Model ◽  
Characteristic Particle

Particle size is an important factor affecting the Thermal-Hydraulic-Mechanical (THM) coupling behavior of graveled rock mass, especially for the shear mechanical properties. In this study, three groups of the particle size range and nine particle grading samples are designed for a large-scale direct shear test. The relationships between shear stress and shear displacement, shear strength, stress ratio, shear strength parameters, and particle breakage of pebble gravel are analyzed. The influence of particle size range and grade on the strength and particle breakage of gravel material is discussed. Results show evident particle breakage in the process of direct shear, and the degree of fragmentation is controlled by the normal load and the particle size distribution of the sample. The shear strength of the sample is no longer applicable to Mohr-Coulomb strength theory because of particle breakage that is more in line with the power function relationship. Shear strength of pebble gravel material has scale effect, and a corresponding relationship model between friction coefficient f of material and characteristic particle size of the sample is proposed.

scholarly journals Investigating the Effect of Rock Bridge on the Stability of Locked Section Slopes by the Direct Shear Test and Acoustic Emission Technique

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 638 ◽  
Author(s):  
Qifeng Guo ◽  
Jiliang Pan ◽  
Meifeng Cai ◽  
Ying Zhang
Keyword(s):  
Acoustic Emission ◽  
Shear Strength ◽  
Normal Stress ◽  
Direct Shear Test ◽  
Shear Test ◽  
Rock Slope ◽  
Direct Shear ◽  
Acoustic Emission Technique ◽  
Rock Bridge ◽  
The Stability

As a portion of intact rock separating joint surfaces, rock bridge plays a significant role in the stability of rock slopes. This paper aims to investigate the effect of different rock bridges on the mechanical properties and failure mode of rock slope by means of the direct shear test and acoustic emission technique. Field conditions were simulated in direct shear tests which were carried out on specimens with rock bridges at different continuity rates, normal stress, arrangements, and joint angles. Experimental results indicate that the strength of specimens is controlled by the rock bridge and the structural plane. The rock bridge contributes to the strength of the specimen, while the through plane weakens the strength of the specimen. The increase of normal stress can weaken the stress concentration near the tip of the rock bridge and improve the shear resistance of the specimen. The different arrangement of rock bridge has little effect on the normal displacement of the specimen, and has a great influence on the shear strength. The shear capacity of the specimen is related to the angle of the crack, and the angle of the crack is approximately proportional to the peak shear strength. For the specimens with different joint occurrence, the mode of crack propagation at the initial stage is basically the same, and the specimen is finally damaged due to the generation of through cracks in the core area of rock bridge. The instantaneous release of the huge energy generated during the experiment along the shear direction is the root cause of the sudden failure of the rock bridge. The formation, aggregation, and transfixion process of rock bridge is of concern and has been experimentally investigated in this paper for the prevention and control of the locked section rock slope with sudden disasters.

scholarly journals Shear Behavior of Frozen Rock-Soil Mixture

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Changqing Qi ◽  
Liuyang Li ◽  
Jihong Wei ◽  
Jin Liu
Keyword(s):  
Shear Strength ◽  
Shear Test ◽  
Vertical Direction ◽  
Shear Behavior ◽  
Initial Water Content ◽  
Peak Shear Strength ◽  
Initial Water ◽  
Soil Mixture ◽  
Shear Process ◽  
Ice Content

Mechanical behavior of frozen rock-soil mixture was investigated through direct shear test based on remolded specimens. The peak shear strength of rock-soil mixture increases greatly when it is fully frozen. The shear process goes through four stages including compaction, elastic deformation, plastic yield, and failure. The specimen has slight compaction in vertical direction at the beginning of shear test; then it changes to dilatancy. The temperature and ice content have vital important effect on the shear behavior of frozen rock-soil mixture. Results indicated that the peak shear strength of rock-soil mixture increases with temperature decreasing when temperature ranges from −1°C to −16°C. But the curve has clear inflexion at −5°C. When temperature is higher than this degree, the peak shear strength increases sharply with temperature decreasing. Otherwise, the rise of the peak shear strength with the decrease of temperature becomes gentle. The shear strength of rock-soil mixture goes up first and then down with ice content increasing at −5°C for samples with initial water contents varying from 9% to 14%. The shear strength reaches its peak value at initial water content ranging between 10% and 12% by weight.

Direct shear behavior of a plane joint under dynamic normal load (DNL) conditions

2016 ◽  
Vol 213 ◽  
pp. 133-141 ◽  
Author(s):  
Wengang Dang ◽  
Heinz Konietzky ◽  
Thomas Frühwirt
Keyword(s):  
Normal Load ◽  
Shear Behavior ◽  
Direct Shear ◽  
Plane Joint

scholarly journals Experimental Study on Shear Mechanism of Rock-Like Material Containing a Single Non-Persistent Rough Joint

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 987
Author(s):  
Sayedalireza Fereshtenejad ◽  
Jineon Kim ◽  
Jae-Joon Song
Keyword(s):  
Shear Strength ◽  
Normal Stress ◽  
Normal Load ◽  
Shear Behavior ◽  
Image Correlation ◽  
Joint Friction ◽  
Rock Bridges ◽  
Shear Mechanism ◽  
Comprehensive Knowledge ◽  
Before And After

The geometrical and mechanical properties of non-persistent joints as well as the mechanical behavior of intact rock (rock bridges) are significantly effective in the shear strength of weakness planes containing non-persistent joints. Therefore, comprehensive knowledge of the shear mechanism of both joints and rock bridges is required to assess the shear strength of the planes. In this study, the shear behavior of specimens containing a single non-persistent rough joint is investigated. A novel procedure was used to prepare cast specimens embedding a non-persistent (disc-shaped) rough joint using 3D printing and casting technology, and the shear strength of the specimens was examined through an extensive direct shear testing program under constant normal load (CNL) condition. Three levels for three different variables of the joint roughness, rock bridge ratio, and normal stress were considered, and the effects of these factors on the shear behavior of prepared samples were tested. The experimental results show a clear influence of the three variables on the shear strength of the specimens. The results show that the normal stress applied to the jointed zone of weakness planes is considerable, and thus joint friction contribution should be taken into account during shear strength evaluation. Furthermore, the dilation mechanism of the specimens before and after failure was investigated through a digital image correlation analysis. Finally, a camcorder was used to analyze the location and sequence of the initiated cracks.

scholarly journals Shear failure modes and AE characteristics of sandstone and marble fractures

2019 ◽  
Vol 11 (1) ◽  
pp. 249-262
Author(s):  
Baohua Guo ◽  
Hangyu Dong
Keyword(s):  
Acoustic Emission ◽  
Failure Modes ◽  
Shear Failure ◽  
Normal Load ◽  
Acoustic Emissions ◽  
Test System ◽  
Sharp Change ◽  
Plastic Shear ◽  
Rock Types ◽  
Shear Process

Abstract To study the shear failure modes of rock fractures with different morphologies, rock types and test conditions, direct shear tests were conducted with the aid of an acoustic emission test system to obtain the characteristics of acoustic emissions in the shear process. The test results indicated that sandstone fractures experienced brittle shear failure under higher constant normal loads (15-30 kN) and plastic shear failure under lower normal loads (5 kN and 10 kN), while the marble fracture experienced plastic shear failure under each normal load. Dropping of shear stress, sharp change from shear dilatation to shear shrinkage and sudden release of high AE energy could be found when brittle shear failure occurred in sandstone fracture under a higher normal load. Thus, combining the location evolution characteristics of acoustic emission, it can be concluded that the entire shear dislocation of sandstone fracture in brittle shear failure mode happened just after the peak under higher normal loads. However, the entire shear dislocation of sandstone fracture under lower normal loads and marble fracture under all normal loads occurred just at the beginning of the shear process.

scholarly journals Experimental Study on Shear Behavior and Acoustic Emission Characteristics of Nonpersistent Joints

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yujing Jiang ◽  
Yongqiang Chen ◽  
Xianzhen Cheng ◽  
Hengjie Luan ◽  
Sunhao Zhang ◽  
...  
Keyword(s):  
Shear Stress ◽  
Acoustic Emission ◽  
Shear Strength ◽  
Fracture Surface ◽  
Crack Length ◽  
Shear Behavior ◽  
Shear Displacement ◽  
Peak Shear Strength ◽  
Rock Discontinuities ◽  
Elastic Stage

The shear behavior of rock discontinuities controls the stability of rock masses to a great extent. In this paper, laboratory shear tests were performed on rock-like materials with different cracks to study the effect of nonpersistent joints on the shear behavior of rock masses. The results show that the variation trends of the shear stress-displacement curves of specimens with different cracks are generally similar and have the same stage characteristics. When the crack length is relatively short, the elastic stage is prolonged, the peak shear strength decreases, and the shear displacement corresponding to the peak shear strength and the residual shear strength increases with the increase of the crack length. When the crack length is relatively long, the elastic stage is shortened, the peak shear strength decreases, and the shear displacement corresponding to the peak shear strength increases with the increase of the crack length. The peak shear stress gradually decreases with the increase of the crack length. The shear strength of the specimens with unilateral cracks is much higher than that of the specimens with bilateral cracks. The shear strength of the specimens is affected not only by the crack length but also by the crack distribution. The acoustic emission (AE) count peak occurs when the shear stress drops sharply and has an inverse “S”-type variation trend with the increase of the crack length. The inclination angle of the fracture decreases, the roughness of the fracture surface decreases, and the proportion of the wear area on the fracture surface increases gradually with the increase of the crack length. The AE source decreases with the increase of the crack length, and their locations are obviously asymmetric. This work can greatly contribute to the insight into the shear failure mechanism of rock discontinuities with nonpersistent joints.

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

2014 ◽  
Vol 9 (3) ◽  
pp. 139-150 ◽  
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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