Anisotropic shear behavior of rock joint replicas

Kumar, Rakesh; Verma, Abhiram Kumar

doi:10.1016/j.ijrmms.2016.10.005

Cited by 63 publications

(12 citation statements)

References 44 publications

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“…Xia et al (2018) carried out an empirical study on shear behaviour. Finally, much work is reported on the development of shear strength models to which Bahaaddini (2016), Casagrande et al (2018), Johansson and Stille (2014), Kumar and Verma (2016), Shrivastava and Seshagiri Rao (2018), and Zhu et al (2019) serve as examples. In summary, these numerous examples illustrate the extent of research performed on joint shearing.…”

Section: Introductionmentioning

confidence: 99%

An Approach to Compensate for the Influence of the System Normal Stiffness in CNS Direct Shear Tests

Larsson

Flansbjer

2020

Rock Mech Rock Eng

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Applying accurate normal load to a specimen in direct shear tests under constant normal stiffness (CNS) is of importance for the quality of the resulting data, which in turn influences the conclusions. However, deficiencies in the test system give rise to a normal stiffness, here designated as system normal stiffness, which results in deviations between the intended and actual applied normal loads. Aiming to reduce these deviations, this paper presents the effective normal stiffness approach applicable to closed-loop control systems. Validation through direct shear tests indicates a clear influence of the system normal stiffness on the applied normal load (13% for the test system used in this work). The ability of the approach to compensate for this influence is confirmed herein. Moreover, it is demonstrated that the differences between the measured and the nominal normal displacements are established by the normal load increment divided by the system normal stiffness. This further demonstrates the existence of the system normal stiffness. To employ the effective normal stiffness approach, the intended normal stiffness (user defined) and the system normal stiffness must be known. The latter is determined from a calibration curve based on normal loading tests using a stiff test dummy. Finally, a procedure is presented to estimate errors originating from the application of an approximate representation of the system normal stiffness. The approach is shown to effectively reduce the deviations between intended normal loads and the actual applied normal loads.

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Section: Introductionmentioning

confidence: 99%

An Approach to Compensate for the Influence of the System Normal Stiffness in CNS Direct Shear Tests

Larsson

Flansbjer

2020

Rock Mech Rock Eng

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“…In addition, water flow or fluid flow in general may change along joints, cleavages or fractures (Köppel et al 2019); or fluid flow may generate even new cracks (Mentes 2019). A number parameters of any rock joint can affect shear resistance to a great degree: water content, the filler material between the sides of a joint, exposure to weather (Barton 1973(Barton , 1976Miščević and Vlastelica 2009), length of joint (Barton and Bandis 1982), surface roughness (Barton 1973;Haberfield and Seidel 1999;Grasselli and Egger 2003;Lee et al 2014), the morphology of surface asperities (Patton 1966;Yang et al 2016;Niktabar et al 2017), the dilation angle (Barton 1973;Kumar and Verma 2016), the contact surface (Zhao 1997;Grasselli and Egger 2003;Pirzada et al 2020), inclination of the joint (Buocz et al 2017), and the compressive strength of the joint (Barton 1973; Barton and Choubey 1977;Lee et al 2014).…”

Section: Introductionmentioning

confidence: 99%

“…Due to the inhomogeneity of a single joint, and because it is difficult to obtain a sufficient number of samples with similar qualities, the use of artificial rock specimens (plaster, cement mortar) with similar qualities to the original rock joints is common in research practice (Patton 1966;Grasselli and Egger 2003;Lee et al 2014;Kumar and Verma 2016;Niktabar et al 2017). In this way, tests are repeatable and it is possible to analyze the effect of a single property on shear strength by keeping the other effective parameters constant.…”

Section: Introductionmentioning

confidence: 99%

“…The failure criterion employed Lee et al (2014) (8) is closer to Barton's (3) and focuses on the joint wall compressive strength measured on cement mortar replicas with high compressive strength (σ c 54.19-83.91 MPa). Kumar and Verma (2016) formed a criterion (10) by analyzing the way in which anisotropic shear behavior is influenced by surface morphology; the tests were conducted on cement mortar joint replicas (σ c 40.83 MPa) at σ n 0.25-1.5 MPa.…”

Section: Introductionmentioning

confidence: 99%

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

Vattai

Rozgonyi-Boissinot

2020

Int J Geomath

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The 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.

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“…An appropriate evaluation of shear behavior of rock joints is vital, for instance, when analyzing the stability of rock slopes, designing excavations in jointed rock, and designing rocksocked piles [1]. A considerable amount of work has been conducted to describe the shear behavior of rock joints [2][3][4][5][6][7][8]. However, in a variety of geomechanical engineering applications, such as rock quarrying, rock drilling, rock excavation, and rock blasting, rock joints may be stressed and failed dynamically [9].…”

Section: Introductionmentioning

confidence: 99%

Dynamic Shear Strength of Rock Joints and Its Influence on Key Blocks

Wang

Xiu

2019

Geofluids

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Shear strength deterioration of rock joints and its induced instability of key blocks subjected to dynamic disturbance constitute the mechanism of many geological disasters such as rockburst, landslide, and rockfall. In this study, the influence of dynamic disturbance on rock joints was quantified in the form of stress, of which model was established by quasistatic method. The dynamic shear strength of rock joints was analyzed theoretically following the Coulomb-Navier criterion and further investigated experimentally by split Hopkinson pressure bar (SHPB) tests with impact velocities of 4.850 m/s, 8.722 m/s, 12.784 m/s, and 16.935 m/s. The effect of engineering disturbance on shear strength of rock joints was measured, and a degradation coefficient was used to describe it quantitatively. Considering the degradation of dynamic shear strength of rock joints and its influence on block stability, the method for determining key blocks under dynamic disturbance was given. Implementing this method into the program of Geotechnical Structure and Model Analysis-3D (GeoSMA-3D) developed by the authors’ team, the visualization of key blocks was achieved. From theoretical analysis and experimental investigation, it was figured out that the shear strength of rock joints is degraded under dynamic disturbance. The degradation of friction angle becomes more sensitive than that of cohesion. Additionally, numerical results show that the number of key blocks was increased with the increasing impact velocities.

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Anisotropic shear behavior of rock joint replicas

Cited by 63 publications

References 44 publications

An Approach to Compensate for the Influence of the System Normal Stiffness in CNS Direct Shear Tests

An Approach to Compensate for the Influence of the System Normal Stiffness in CNS Direct Shear Tests

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

Dynamic Shear Strength of Rock Joints and Its Influence on Key Blocks

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