scholarly journals Analysis of the shear failure of surface methane capture boreholes for improving the drainage period efficiency: A lithological perspective

2019 ◽  
Vol 38 (1) ◽  
pp. 92-110
Author(s):  
Hongjie Xu ◽  
Zezhong Fang ◽  
Shuxun Sang ◽  
Huihu Liu ◽  
Hai Ding ◽  
...  
Keyword(s):  
Shear Strength ◽  
Shear Failure ◽  
Borehole Stability ◽  
Protective Measures ◽  
Direct Shear Tests ◽  
Rock Types ◽  
Lower Shear ◽  
The Stability ◽  
Rock Specimens ◽  
High Quartz

The shear failure of surface methane capture boreholes (SMCBs) is the main reason for the life cycle shortening of surface methane capture boreholes but lacks a comprehensive lithological analysis. To improve the surface methane capture borehole stability and drainage period efficiency, it is of great importance to investigate the influence of lithology on the shear failure of surface methane capture boreholes. The results of direct shear tests and geological investigations show that the shear displacement increases as the grain size decreases. A jump in mechanical properties occurs at the lithological boundaries and is mainly controlled by the composition of the rock specimens. The change in cohesion is the main possible reason for the step change of the shear strength. High quartz and low clay contents may effectively improve the shear strength and failure resistance of rock. Boreholes may potentially experience preferential casing failure in the section of the weaker mudstone and siltstone due to larger shear displacements and lower shear strengths of those rock types. Protective measures at these sections may improve the stability of the borehole casing. The detection results at the close of the borehole verify the prediction.

scholarly journals Analysis of Shear Failure of Surface Methane Capture Boreholes for Improving Efficient Drainage Period–A Lithology Perspective

2019 ◽  
Author(s):  
Hongjie Xu ◽  
Zezhong Fang ◽  
Shuxun Sang ◽  
Jingfen Yang ◽  
Huihu Liu ◽  
...  
Keyword(s):  
Shear Strength ◽  
Shear Failure ◽  
Shear Displacement ◽  
Shear Tests ◽  
Protective Measures ◽  
Failure Resistance ◽  
Direct Shear Tests ◽  
The Stability ◽  
Rock Specimens ◽  
High Quartz

The shear failure of surface methane capture borehole (SMCB) is the main cause of shortening life cycle of SMCB but lack of lithological analysis. In order to improve the stability of SMCB and improve efficient drainage period, it is of great significance to investigate the lithology performances for shear failure of SMCB. Based on the direct shear tests and geological method, the results shows that the shear displacement increases as the grain size decreases. Mechanical jump occurs at the lithological boundaries, which is mainly determined by the composition of rock specimens. The cohesion is the mainly possible reason for the step change of shear strength. Lithology with high quartz and low clay may effectively improve shear strength and failure resistance. Boreholes drilled into the weaker siltstone and mudstone sections may potentially experience preferential damage due to the larger shear displacement and shear strength. Protective measures at these sections may improve the stability of the borehole casing. The probing data where it was found that boreholes closure validated the prediction.

scholarly journals Prediction of the Shear Failure of Opened Rock Fractures and Implications for Rock Slope Stability Evaluation

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Yingchun Li
Keyword(s):  
Shear Strength ◽  
Rock Slope ◽  
Shear Failure ◽  
Rock Slope Stability ◽  
Rock Fractures ◽  
Asperity Contact ◽  
Direct Shear Tests ◽  
Proposed Model ◽  
The Stability ◽  
New Criterion

Rock slope commonly fails due to the shear failure of rock fractures. Shear strength of rock fractures are reduced substantially once the fracture surfaces are mismatched or opened. We propose a new criterion to predict the shear strength of rock fractures in different opening states. The degree of interlocking representing the true asperity contact area is incorporated into the modified model of Saeb and Amadei. The effect of fracture opening on asperity dilation and degradation is separately considered. The transitional stress that is a critical parameter involved in the model is analytically determined based on energy consideration. The new model is validated with experimental results from direct shear tests on synthetic fractures with regular-shaped asperities. Good agreement between the analytical solution and the experimental data confirms the capacity of the proposed model. Therefore, the model has great potential for assessing the stability of rock slopes where fractures are often opened due to stress relief and engineering disturbances.

scholarly journals Brief communication: The influence of mica-rich rocks on the shear strength of ice-filled discontinuities

2020 ◽  
Vol 14 (6) ◽  
pp. 1849-1855
Author(s):  
Philipp Mamot ◽  
Samuel Weber ◽  
Maximilian Lanz ◽  
Michael Krautblatter
Keyword(s):  
Shear Strength ◽  
Failure Criterion ◽  
Rock Slopes ◽  
Surface Charges ◽  
Permafrost Rock ◽  
Rock Types ◽  
Negative Surface ◽  
The Stability ◽  
Stress Dependent ◽  
Dependent Failure

Abstract. A temperature- and stress-dependent failure criterion for ice-filled rock (limestone) joints was proposed in 2018 as an essential tool to assess and model the stability of degrading permafrost rock slopes. To test the applicability to other rock types, we conducted laboratory tests with mica schist and gneiss, which provide the maximum expected deviation of lithological effects on the shear strength due to strong negative surface charges affecting the rock–ice interface. Retesting 120 samples at temperatures from −10 to −0.5 ∘C and normal stress of 100 to 400 kPa, we show that even for controversial rocks the failure criterion stays unaltered, suggesting that the failure criterion is transferable to mostly all rock types.

Slope Stability Analysis in Anisotropic Winnipeg Clays

1974 ◽  
Vol 11 (1) ◽  
pp. 59-71 ◽  
Author(s):  
W. S. Freeman ◽  
Hugh B. Sutherland
Keyword(s):  
Shear Strength ◽  
Cross Sections ◽  
Strength Properties ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Residual Shear Strength ◽  
Lower Shear ◽  
The Stability ◽  
Mechanism Of Failure ◽  
Cut Slopes

Two major aspects of an investigation dealing with the stability of natural and cut slopes in the Winnipeg area are described. The first concerns an experimental investigation of the anisotropic shear strength characteristics of the layered Lake Agassiz clays and the second is a study of the mechanism of failure for slopes in these layered clays.Four main types of clay were investigated and it was found that the effective shear strength parameters were greater for failure across the layers than for failure along the layers. Residual shear strength parameters were also determined.Stability analyses were carried out for representative slope cross sections using circular and noncircular failure surfaces, taking into account the anisotropic shear strength effects measured in the laboratory tests.Factors of safety were found for the conventional method of analysis assuming circular arc failure surfaces and isotropic shear strength properties. These factors of safety were found to be up to 0.5 greater than those obtained from noncircular failure surfaces which partially passed along the layers and so mobilized the lower shear strength properties of these layers.

scholarly journals Change Mechanism of Strength of Soil-rock Mixture Freezing-thawing Interface under Different Rock

2021 ◽  
Author(s):  
Li Gang ◽  
Huang Tao ◽  
Li Zhen ◽  
Bai Miaomaio
Keyword(s):  
Shear Strength ◽  
Shear Failure ◽  
Laser Scanner ◽  
Shear Plane ◽  
Failure Surface ◽  
Calculation Model ◽  
Bite Force ◽  
Direct Shear Tests ◽  
Change Mechanism ◽  
The Impact

With global warming and accelerated degradation of permafrost, the engineering problems caused by the formation of weak zones between the shallow and permafrost layers of soil–rock mixture (S-RM) slopes in permafrost regions have become increasingly prominent. To explore the influence of rock content on the shear strength of the S-RM freezing–thawing interface, the variation in the shear strength for different rock content is studied herein using direct shear tests. In addition, a 3D laser scanner is used for obtaining the topography of the shear failure surface. Combined with the analysis results of the shear band-particle calculation model, the influence of the rock content on the shear strength of the interface is explored. It was found that the impact threshold of the rock content on the interface strength and failure mode is approximately 30%, when the rock content (R) is > 30% and that the shear strength increases rapidly with increasing rock content. When R ≤ 30%, the actual shear plane is similar to waves; when R > 30%, the shear plane appears as gnawing failure. The shear strength of S-RM freezing–thawing interface mainly comes from the bite force and friction between particles. The main reason for the increase in shear strength with increasing rock content is the increase in bite force between particles, which makes the ratio of bite force to friction force approximately 1:1.

Experimental Study on Shear Behavior of Short-Fill-Age MSW

2010 ◽  
Vol 113-116 ◽  
pp. 479-483
Author(s):  
Li Sha Ma ◽  
Huan Li Wang ◽  
Wei Wang ◽  
Zheng Wen Zhang
Keyword(s):  
Shear Strength ◽  
Shear Failure ◽  
Friction Angle ◽  
Exponential Model ◽  
Hyperbolic Model ◽  
Displacement Curve ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Cohesion Force ◽  
Coulomb Criterion

Mechanical behavior of municipal solid waste (MSW) is important to geo-environment engineering, and it is necessary to properly understand it. Laboratory direct shear tests were conducted on MSW with 3 short fill ages, namely 1d, 4d and 7d. Three different densities were taken into accounted in each fill age. Experimental data show that MSW’s shear failure still satisfies the Mohr-Coulomb criterion. As to bigger density, shear strength of MSW increases within 1-7d fill age. When density becomes smaller, its shear strength increases within 1-4d fill age but decreases within 4-7d fill age. With fill-age developing, friction angle of MSW increase monotonously, but cohesion force of it first increases and then decreases. Experimented shear stress-displacement curve of MSW can not be well fitted by either hyperbolic model or exponential model. This experimental research is helpful for design and numerical simulation of corresponding MSW landfill.

Experimental Study on Structural Properties Influencing on Shear Strength of Soft Clay

2011 ◽  
Vol 243-249 ◽  
pp. 2487-2490
Author(s):  
Jiang Feng Wang ◽  
Yong Le Li ◽  
Yan Bin Gao ◽  
Yong Xiang Yang
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Shear Failure ◽  
Clayey Soil ◽  
Soft Clay ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Undisturbed Soil ◽  
Direct Shear Tests ◽  
Reconstituted Soil

The direct shear tests were conducted with undisturbed and reconstituted soft clay, then the structural influence on shear strength was studied, and the laws were got. No matter shear strength of slow shear or consolidated quick shear on undisturbed and reconstituted soil have not peak values, strength line of reconstituted soil is a slash, but the shear strength line of undisturbed soil is obviously a broken line. The internal friction angle of undisturbed and reconstituted soil is basically the same. There are good linear relationship between internal friction angle and plastic index of clayey soil. The amplitude of internal friction angle of reconstituted soil decreasing with plastic index increasing is less than that of undisturbed soil. From wf-lgp curve can be seen, with the increasing of vertical stress, water content of shear failure decrease gradually, and linear correlation of each curve is very good.

scholarly journals Effect of Bedding Orientation and Spatial Variability of Stratification Shear Strength on Stability of Transversely Isotropic Rock Slope

2021 ◽  
Vol 9 ◽  
Author(s):  
Su-Hua Zhou ◽  
Shuai-Kang Zhou ◽  
Jiu-Chang Zhang ◽  
Xin Tan
Keyword(s):  
Shear Strength ◽  
Spatial Variability ◽  
Transversely Isotropic ◽  
Transversely Isotropic Rock ◽  
Direct Shear Tests ◽  
Isotropic Rock ◽  
Bedding Planes ◽  
Dip Angle ◽  
The Stability ◽  
Surface Changes

The spatial variability of soil properties is inherent. A series of direct shear tests were carried out on strongly weathered slates samples with weak bedding planes, the result of which indicates the existence of variability of shear strength parameters. Based on the testing results, several numerical simulations of slopes were conducted considering such a variability of shear strength. The results had shown that the weak bedding planes affect the shape of sliding arc as well as the factor of safety of slopes. As the dip angle of bedding planes increases, the shape of the sliding surface changes from circular to a mixed form of circular and planner. When incorporating the spatial variability of weak planes’ shear strength into the stability analysis, the safety factors of slopes would reduce, in which the sliding arc exhibited a sliding band comprising multiple sets of sliding arcs.

Effect of roughness on shear behavior of red clay – concrete interface in large-scale direct shear tests

2015 ◽  
Vol 52 (8) ◽  
pp. 1122-1135 ◽  
Author(s):  
Xiaobin Chen ◽  
Jiasheng Zhang ◽  
Yuanjie Xiao ◽  
Jian Li
Keyword(s):  
Surface Roughness ◽  
Shear Strength ◽  
Large Scale ◽  
Shear Failure ◽  
Friction Angle ◽  
Confining Pressure ◽  
Shear Behavior ◽  
Interfacial Shear ◽  
Red Clay ◽  
Direct Shear Tests

Few studies have focused on evaluating regular surface roughness and its effect on interfacial shear behavior of the red clay – concrete interface. This paper presents the results of a series of laboratory large-scale direct shear tests conducted using different types of red clay – concrete interfaces. The objective is to examine the effect of surface roughness on these types of soil–concrete interfaces. In the smooth-interface tests, the measured peak and residual shear strength values are very close to each other, with no observed shear dilation. The surface roughness is found to have a remarkable effect on the interfacial shear strength and shear behavior, with the shear strength increasing with increased surface roughness level. The shear dilation is likely to occur on rougher interfaces under lower confining pressure due to the behavior of compressed clay matrices. Owing to the clay matrix’s cohesion and friction, the interfacial shear strength on rough interfaces consists of cohesive and frictional forces between the clay and concrete surfaces. The friction angle value is observed to fluctuate between the clay’s friction angle and the smooth interface’s friction angle. This can be related to the position change of the shear failure slip plane. The confining pressure and surface roughness could change the shear failure plane’s position on the interface. Furthermore, the red clay – structure interface is usually known as the weakest part in the mechanical safety assessment.

Current Induced Interfacial Microstructure and Strength Weakening of SAC/FeNi-Cu Connection

2014 ◽  
Vol 651-653 ◽  
pp. 11-15 ◽  
Author(s):  
Xiao Jing Wang ◽  
Tian Yang Li ◽  
Yun Xia Chen ◽  
Jian Xin Wang
Keyword(s):  
Shear Strength ◽  
Intermetallic Compound ◽  
Shear Failure ◽  
Interfacial Microstructure ◽  
Thickness Variation ◽  
Interface Microstructure ◽  
Current Stressing ◽  
Film Layer ◽  
The Stability ◽  
Current Exposure

The interface microstructure and shear strength weakening of eutectic SnAgCu (SAC)/FeNi-Cu connection after current stressing for 0~12 h were investigated to discuss the stability of the FeNi layer as UBM film layer for Sn base solder. The experiments showed that the FeNi layer separated to two layers with different Fe/Ni ratio rather than intermetallic compound (IMC) thickness variation between the cathode and anode. The IMCs became rougher with a bulk amount of (Cu,Ni)6Sn5 emerging in the regains near to interfaces. The shear failure mode exhibited a ductile manner companied by a fracture surface rougher and even grain boundary weakening with the current exposure time increasing.

Sign in / Sign up

Export Citation Format

Share Document