scholarly journals Photogrammetric Prediction of Rock Fracture Properties and Validation with Metric Shear Tests

Geosciences ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 293
Author(s):  
Lauri Uotinen ◽  
Masoud Torkan ◽  
Alireza Baghbanan ◽  
Enrique Caballero Hernández ◽  
Mikael Rinne
Keyword(s):  
Shear Strength ◽  
Rock Fracture ◽  
Friction Angle ◽  
Jointed Rock ◽  
Roughness Coefficient ◽  
Rock Fractures ◽  
Shear Tests ◽  
Large Sample ◽  
Peak Friction Angle ◽  
Peak Shear Stress

An accurate understanding of jointed rock mass behavior is important in many applications ranging from deep geological disposal of nuclear waste, to deep mining, and to urban geoengineering projects. The roughness of rock fractures and the matching of the fracture surfaces are the key contributors to the shear strength of rock fractures. In this research, push shear tests with three normal stress levels of 3.6, 6.0, and 8.5 kPa were conducted on two granite samples with artificially induced well-matching tensile fractures with sizes of 500 mm × 250 mm and 1000 mm × 500 mm. The large sample reached on average a −60% weaker peak shear stress than the medium-sized sample, and a strong negative scale effect was observed in the peak shear strength. The roughness of the surfaces was measured using a profilometer and photogrammetry. The scale-corrected profilometer-based method (joint roughness coefficient, JRC) underestimates the peak friction angle for the medium-sized slabs by −27% for the medium sample and −9% for the large sample. The photogrammetry-based (Z′2) method produces an estimate with −7% (medium) and + 12% (large) errors. The photogrammetry-based Z′2 is an objective method that consistently produces usable estimates for the JRC and peak friction angle.

scholarly journals Prediction of Peak Friction Angle using Photogrammetry and Comparison to Shear Test Results of Metric Scale Rock Fractures

2021 ◽  
Author(s):  
Lauri Uotinen ◽  
Masoud Torkan ◽  
Alireza Baghbanan ◽  
Enrique Caballero Hernández ◽  
Mikael Rinne
Keyword(s):  
Shear Strength ◽  
Friction Angle ◽  
Jointed Rock ◽  
Rock Fractures ◽  
Deep Mining ◽  
Large Sample ◽  
Peak Friction Angle ◽  
Peak Shear Stress ◽  
Deep Geological Disposal ◽  
Tensile Fractures

An accurate understanding of jointed rock mass behavior is important in many applications ranging from deep geological disposal of nuclear waste to deep mining to urban geoengineering projects. The roughness of rock fractures and the matching of the fracture surfaces are the key contributors to the shear strength of rock fractures. In this research, push shear tests with three normal stress levels of 3.6, 6.0, and 8.5 kPa were conducted with two granite samples with artificially induced well-matching tensile fractures with sizes of 500 mm × 250 mm and 1000 mm × 500 mm. The large sample reached on average a -60 % weaker peak shear stress than the medium-sized sample, and a strong negative scale effect was observed in the peak shear strength. The roughness of the surfaces was measured using a profilometer and photogrammetry. The scale-corrected profilometer-based method (JRC) underestimates the peak friction angle for the medium-sized slabs by -27 % for the medium sample and -9 % for the large sample. The photogrammetry-based (Z’2) method produces an estimate with -7% (medium) and +12 % (large) errors. The photogrammetry-based Z’2 is an objective method that consistently produces usable estimates for the JRC and peak friction angle.

scholarly journals The effects of grain size and different multi-stage shearing techniques on shear strength along rock discontinuities

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Alina Vattai ◽  
Nikoletta Rozgonyi-Boissinot
Keyword(s):  
Grain Size ◽  
Shear Strength ◽  
Normal Stress ◽  
Friction Angle ◽  
Coarse Grained ◽  
Roughness Coefficient ◽  
Peak Friction Angle ◽  
Grain Sizes ◽  
Multi Stage ◽  
Study Laboratory

AbstractThe effects of grain size and different multi-stage shearing techniques on shear strength along discontinuities were analyzed in this study. Laboratory direct shear tests were carried out on plaster mortar with maximum grain sizes of 0.5 mm and 1.0 mm. All specimen surfaces were essentially similar, copied from the same natural, Hungarian coarse-grained sandstone joint with a low joint roughness coefficient (JRC = 8). Tests within two different normal stress ranges (σn = 0.25–0.5 and 0.5–1.5 MPa) were performed simultaneously. Specimens tested using the technique involving modified shearing with repositioning were sheared three times while being subjected to the same degree of normal stress (shearing sequence n = 1, 2, 3) and those with multi-stage technique without repositioning were subjected to shearing once at three different degrees of normal stress. The changing values of the peak friction angle calculated from the resulting peak shear strength-normal stress data pairs (τp − σn) were examined. Failure curves were estimated using linear regression, according to the Mohr–Coulomb failure criterion. The differences between the various peak friction angles obtained from experiments in which different multi-stage shearing techniques were used tend to increase in significance with the increasing number of shearing sequences. Peak friction angle values vary according to grain size of the material, though further investigations using more grain sizes are required to establish the extent of the effect on shear strength along discontinuities.

scholarly journals Field and Laboratory-based Approach for the Determination of Friction Angle of Geological Discontinuities of Malaysian Granites

2011 ◽  
Vol 28 (2) ◽  
pp. 151 ◽  
Author(s):  
R. A Ghani ◽  
T. L Goh ◽  
A. M Hariri ◽  
Y. N Baizura
Keyword(s):  
Friction Angle ◽  
Roughness Coefficient ◽  
Average Value ◽  
Peak Friction Angle ◽  
Maximum Value ◽  
Wide Range ◽  
Discontinuity Surfaces ◽  
Geological Discontinuities ◽  
Range Of Values

The basic friction angle, Φb for artificially sawn discontinuity planes for fresh granite, as determined by tilt testing, has an average value of 30º. For the natural rough discontinuity surfaces, a wide range of values have been determined for the peak friction angle, Φpeak ranging from 47º to a maximum value of 80º, depending on the joint roughness coefficient (JRC). The average values of the friction angles for the different degrees of roughness were as follows: JRC 2–4 = 58°; JRC 6–8 = 60°; JRC 8–10 = 47°; JRC 12–14 = 60°; JRC 14–16 = 71° ; JRC 18–20 = 80°.

scholarly journals Tensile and Shear Mechanical Characteristics of Longmaxi Shale Laminae Dependent on the Mineral Composition and Morphology

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2977
Author(s):  
Lihui Li ◽  
Beixiu Huang ◽  
Xiaolin Huang ◽  
Ming Wang ◽  
Xiao Li
Keyword(s):  
Shear Strength ◽  
Friction Angle ◽  
Fracture Morphology ◽  
Shear Tests ◽  
Fracture Surface Roughness ◽  
Lower Silurian ◽  
Angle Fracture ◽  
Longmaxi Shale ◽  
Tensile Fracturing ◽  
Shear Behaviors

Laminae are well developed in shale and generally influence fracture propagation during hydraulic fracturing. Hence, comprehensively understanding the tension and shear behaviors of shale laminae is crucial. There have been limited systematic studies thus far on the tensile and shear strength as well as fracture morphology of shale laminae. In this study, the Lower Silurian Longmaxi Shale (China) was investigated via Brazilian tensile and angle-varied plate shear tests. Five lamina types were tested, i.e., calcite (Cal), pyrite (Py), organic-enriched (Oc), the interface between Cal and Oc (Cal-Oc), and the interface between Py and Oc (Py-Oc) laminae. Results showed that the tensile strength was in the range 0.43–8.22 MPa, mainly in the order of Cal > Py > Cal-Oc > Py-Oc > Oc. The modes of fracture morphology were highly related to the occurrence, continuity, and mineralogy fillings of laminae. Shear strength parameters were within the range 22.50–29.64 MPa for cohesion and 37.29–43.60° for internal friction angle. Fracture surface roughness was strongly related to its cohesion. Calcite laminae considerably influenced the tensile fracturing of shale, suggesting that the geometry and properties of calcite lamina should receive more attention during the design of shale gas exploration.

scholarly journals DEVELOPMENT OF A MODEL FOR THE ESTIMATION OF SHEAR STRENGTH OF DISCONTINUITY IN MASSIVE AND KARSTIFIED LIMESTONE

2021 ◽  
Vol 36 (2) ◽  
pp. 43-57
Author(s):  
Ivana Dobrilović ◽  
Petar Hrženjak ◽  
Dražen Navratil
Keyword(s):  
Shear Strength ◽  
Field Research ◽  
Friction Angle ◽  
Roughness Coefficient ◽  
Engineering Practice ◽  
Filling Material ◽  
Dimension Stone ◽  
Large Samples ◽  
Proposed Model ◽  
Made In

In this paper, the problem of estimating the shear strength of discontinuity is presented, which especially occurs in massive and karstified limestones, where discontinuity walls can be extremely rough and irregular, with or without filling material, and for which the current models have proven to be unsatisfactory. A characteristic example of such limestones is the deposit of dimension stone “Kanfanar”, located on the Istrian peninsula in Croatia. For the purpose of developing a model for estimating the shear strength of discontinuity, field research was conducted in which large samples of blocks with natural discontinuities were prepared, as well as samples of filling material in limited conditions, on which detailed laboratory tests of shear strength were performed. Special attention was paid to determining the joint roughness coefficient JRC, the actual contact area between the discontinuity walls, the basic or residual friction angle and the friction angle of the built-in filling material between the discontinuity surfaces. The development of the model for estimating the shear strength of discontinuity was based on Barton’s JRC-JCS empirical model, given the fact that it is one of the most commonly applied models in engineering practice. Based on the results of the tests, a modification of Barton’s JRC-JCS model was made, in such a way that the friction angle of the built-in filling material in the case of discontinuity with a filling was applied instead of the basic or residual friction angle. In addition, for the correct evaluation of the roughness of the discontinuity walls in massive and karstified limestones, it was found that it is necessary to increase the roughness coefficient to values larger than 20, which has been proposed as the maximum so far. Evaluation of the proposed model showed that it is satisfactorily accurate in estimating the shear strength of discontinuity with clay filling material of different states of consistency.

scholarly journals Analysis of Changes in the Micromorphology of Sandstone Joint Surface under Dry-Wet Cycling

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Jingcheng Fang ◽  
Huafeng Deng ◽  
Yu Qi ◽  
Yao Xiao ◽  
Hengbin Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Friction Angle ◽  
Jointed Rock ◽  
Joint Surface ◽  
Roughness Coefficient ◽  
Rock Masses ◽  
Jointed Rock Masses ◽  
Bank Slope ◽  
Steep Decrease ◽  
The Face

Changes in the micromorphology of joint surface under dry-wet cycling have a direct effect on the mechanical properties of the jointed rock masses, which in turn affects the deformation stability of the bank slope of a reservoir. In this study, we design and carry out a test that aims to quantity the effects of repeated rise and fall of a reservoir on the properties of a jointed rock masses. The results are as follows: first, the roughness, local gradient, and undulation of the joint surface gradually decreased under repeated dry-wet cycling. In addition, the height parameters and texture parameters showed a steep decrease followed by a slow decline. The deterioration was particularly obvious over the first 5 dry-wet cycles. Second, the roughness coefficient of the joint surface, the compressive strength of the face wall, and the basic friction angle were gradually reduced under dry-wet cycling. The shear strength of the jointed rock masses (obtained both quantitatively and experimentally) showed a deteriorating trend controlled by the deterioration of the micromorphology, the strength of the face wall, and the frictional properties of the joint surface. Finally, the dry-wet cycling process determined trends of changes in the microstructure parameters and mechanical properties of the joint surface. Our research results provide a good basis for the analysis of the deterioration and failure of rock masses within the hydrofluctuation belt of a bank slope.

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.

scholarly journals Determination of the Effect of Soil Particle Size Distribution on the Shear Behavior of Sand

2021 ◽  
Vol 5 (2) ◽  
pp. 125
Author(s):  
Mohammad Afrazi ◽  
Mahmoud Yazdani
Keyword(s):  
Particle Size ◽  
Shear Strength ◽  
Direct Shear Test ◽  
Shear Test ◽  
Friction Angle ◽  
Particle Sizes ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests

Many geotechnical problems require the determination of soil engineering properties such as shear strength. Therefore, the determination of the reliable values for this parameter is essential. For this purpose, the direct shear test, as one of the oldest tests to examine the shear strength of soils, is the most common way in laboratories to determine the shear parameters of soil. There are far too many variables that influence the results of a direct shear test. In this paper, a series of 10 × 10 cm direct shear tests were carried out on four different poorly graded sands with different particle size distributions to determine their shear behaviors. Four different poorly graded sands with a different median diameter or medium value of particle size distribution (D50) (0.2, 0.53, 1.3, and 2.3 mm) has been selected, and about 40 direct shear tests were conducted. It was concluded that a soil’s friction angle is affected by coarse-grained material. Accordingly, sandy soils with bigger particle sizes record a higher friction angle than soils containing small particles. The investigations also showed that sand with bigger particle sizes has a higher dilation angle. In addition, a non-linear regression analysis was performed to establish the exact relationship between the friction angle of the soil and the characteristics of the soil particles. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Calculations on Roughness of Rock Fracture Based on Image Processing

2012 ◽  
Vol 256-259 ◽  
pp. 203-206
Author(s):  
Xiao Bo Yu ◽  
Yang Song Zhang ◽  
Ruo Yao Li
Keyword(s):  
Rock Fracture ◽  
Gansu Province ◽  
Rock Joints ◽  
Nuclear Waste Repository ◽  
Roughness Coefficient ◽  
Rock Fractures ◽  
High Radiation ◽  
Deformation Parameters ◽  
Strength And Deformation ◽  
The Relationship

Joint roughness coefficient (JRC) is an important factor in the evaluation of the shear strength and deformation parameters of rock joints. This paper presents a method for measuring JRC of rock fractures based on digital image progressing technique. Though preprocessing of the rock fracture image, the skeleton of the fracture was got, the rough degree were analyzed and quantized by geometric parameters of the skeleton. By establishing the relationship between JRC and the rough degree, JRC will be got though the rough degree. This method improves automation degree and accuracy comparing to the previous methods. Finally this method was used to get the JRC of rock fracture in Jijicao, Beishan, Gansu province, where may be the high-radiation nuclear waste repository.

Exploring the effects of nanoscale zero-valent iron (nZVI) on the mechanical properties of lead-contaminated clay

2019 ◽  
Vol 56 (10) ◽  
pp. 1395-1405 ◽  
Author(s):  
Yong-Zhan Chen ◽  
Wan-Huan Zhou ◽  
Fuming Liu ◽  
Shuping Yi
Keyword(s):  
Shear Strength ◽  
Triaxial Compression ◽  
Morphological Characteristics ◽  
Friction Angle ◽  
Zero Valent Iron ◽  
Compression Tests ◽  
Shear Tests ◽  
Nanoscale Zero Valent Iron ◽  
Triaxial Compression Tests ◽  
Oedometer Tests

Nanoscale zero-valent iron (nZVI) is a well-known efficient nanomaterial for the immobilization of heavy metals and has been widely applied in the remediation of contaminated groundwater and soils. In this study, a series of field emission scanning electron microscopy (FESEM) analyses, vane shear tests, triaxial compression tests, and oedometer tests was conducted on lead-contaminated clay using four dosages of nZVI treatment (0.2%, 1%, 5%, and 10%). The geotechnical properties, including basic index properties, stiffness, shear strength, and compressibility, were assessed after the reaction procedure. FESEM analysis was performed to explore the potential mechanisms of nZVI treatment in terms of morphological characteristics. It was found that the plasticity index decreased gradually with increasing nZVI dosage. Treating contaminated soil with nZVI caused an increase in the vane shear strength, stiffness, and friction angle. The compression index increased gradually because of the nZVI treatment. Based on the FESEM analysis, a conclusion can be deduced that larger aggregates and conjoined structures resulting from nZVI treatment can lead to the strengthening of lead-contaminated clay.

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