Experimental Investigation of Anisotropic Wear Damage for Natural Joints under Direct Shearing Test

Jiang, Quan; Song, Leibo; Yan, Fengyuan; Liu, Chang; Yang, Bin; Xiong, Jun

doi:10.1061/(asce)gm.1943-5622.0001617

Cited by 27 publications

(5 citation statements)

References 50 publications

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“…Grasselli (2006) pointed out that the difference in peak resistance between the first shear test and the subsequent shear test is attributed to the change in micro-roughness. Hong et al (2016) and Jiang et al (2020) also confirmed that the degradation of smallscale asperities plays a significant role in mobilizing the peak shear strength. Therefore, the alteration of the surface geometry resulting from the shearing, namely, the difference in roughness between the fresh and sheared surfaces, should be distinguished and recognized as an essential factor for various research issues related to jointed rock (e.g., the drop in peak shear strength of the rock joint during cyclic shear tests and the constitutive model for a sheared rock joint reflecting the surface roughness).…”

Section: Introductionmentioning

confidence: 58%

Roughness Evaluation for Distinguishing Fresh and Sheared Rock Joint Surfaces with Different Sampling Intervals

2021

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The subtle alteration of surface geometry from a fresh surface to a sheared surface usually results in a considerable variation in the shear strength of jointed rock mass.Through profiling surfaces of the granite joints before and after the shear tests, an evaluation scheme was newly proposed by determining a desirable characteristic index and sampling interval of surface measurement in order to distinguish fresh and sheared joint surfaces quantitatively. The measured data demonstrated that although the mean Z2 (root mean square first derivation) values of all the profile lines were confirmed reasonable for estimating the JRC (joint roughness coefficient) value of the fresh joint surface, it could not completely evaluate the roughness of the sheared joint surfaces.Meanwhile, the distribution of slope angles, as the characteristic parameter, was proved enable to clearly distinguish the fresh and sheared rock joint surfaces incorporating the small sampling scales (<= 0.1 mm). The numerical simulations implemented in a mechanical shear model could confirm the critical effect of a slight change in surface geometry, and further prove that the sampling interval of 0.1 mm could sufficiently capture the evolved "waviness" and "unevenness" of rock joint surfaces. Overall, it was confirmed that the results of our study provide new clues for evaluating the surface roughness of fresh and sheared rock joints and can be beneficial for understanding the variation of surface geometry during the shear process.

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Section: Introductionmentioning

confidence: 58%

Roughness Evaluation for Distinguishing Fresh and Sheared Rock Joint Surfaces with Different Sampling Intervals

2021

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“…As no two natural rock joint specimens are truly identical, it is difficult to obtain a large number of specimens with the same morphology [74]. Therefore, when testing schemes require multiple specimens, joint specimens with natural surfaces are produced mainly by copying techniques, such as creating fractures by splitting, sawing flat joints with undulated or irregular surfaces, and casting natural or stylized joints with silicon or rubber molds.…”

Section: Joint Specimen Preparation and Test Schemesmentioning

confidence: 99%

A New Characterization Method for Rock Joint Roughness Considering the Mechanical Contribution of Each Asperity Order

Yuan

Luo

et al. 2021

Applied Sciences

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The morphology of the joint surface is multi-scale, and it can be divided into first-order asperity (waviness) and second-order asperity (unevenness). At present, the joint roughness characterization formula considers only the morphology contribution of waviness and unevenness components and does not fully consider their mechanical contribution. At same time, the relationship between the mechanical contribution and the morphology contribution is still unclear. Thus, the characterization formula considering the mechanical contribution of waviness and unevenness needs to be further studied. In this study, the standard joint roughness coefficient (JRC) profiles were first decomposed into waviness and unevenness. Then, three types of joint specimens with different asperity orders (flat, the standard JRC profile, and the profile containing only waviness) were prepared by the 3D engraving technique. Finally, direct shear tests were carried out on 39 sets of red sandstone joint specimens under three normal stresses. The mechanical contributions of waviness and unevenness were studied, the relationship between the mechanical contribution and the morphology contribution of waviness and unevenness was analyzed, and the characterization formula considering the mechanical contribution of waviness and unevenness was established. The results showed that the following: (1) the method combining the ensemble empirical mode decomposition (EEMD) and the critical decomposition level could be used to separate the waviness and unevenness from the joint surface; (2) the mechanical contribution of the waviness and unevenness decreased with the increase in normal stress; (3) the relationship between the mechanical contribution ratio and the statistical parameter ratio of the waviness and unevenness can be describe by power function; and (4) the roughness characterization formula considering the mechanical contribution and morphology contribution was established. This study will enhance the accurate evaluation of the roughness coefficient and shear strength of the joint specimen.

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“…The morphology of the damaged area is complex, so it is not easy to quantify the damaged area accurately through two-dimensional (2D) image analyses. In this study, a new method to quantify the joint damage ratio and damage volume was proposed [46]. The realization of this method can be divided into three steps [47]: (1) get the point cloud data of the joint surface before and after shear, (2) align the point cloud data of the joint surface before and after shear by the ICP algorithm, and (3) calculate the height deviation and damage volume by the Matlab code; the code can be found in Appendix 3.…”

Section: Asperity Order Effect On the Damage Ratiomentioning

confidence: 99%

Exploring the Effect of Asperity Order on Mechanical Character of Joint Specimen from the Perspective of Damage

Yuan

Luo

2021

Geofluids

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The joint morphology is multiscale. The effect of each asperity order on the mechanical properties of joints is different. The shear mechanical properties of joint specimens are related to its surface damage characteristics. At present, there are still few studies on the effect of roughness on the shearing mechanical properties of joint from the perspective of damage of each asperity order. In this paper, the standard roughness profile was chosen as initial morphology. The standard roughness profile was decomposed into waviness and unevenness by the method combine the ensemble empirical mode decomposition (EEMD) and the cut-off criterion. Then, the joint specimen which contains waviness and unevenness and the specimen which only contains waviness were prepared by the 3D engraving technology. The 40 sets of joint specimens with different asperity order were subjected to direct shear tests under different normal stresses. Based on the 3D scanning technology and ICP iterative method, the damaged area and the damage volume were calculated. Based on the damage volume data and the acoustic emission (AE) data, the effect of asperity order to the joint mechanical behaviour was studied. The results indicate that (1) under low normal stress, the unevenness plays a control role in the failure mode of the joint specimen. Under low normal stress, the joint surface containing only waviness exhibits slip failure, and the joint surface with unevenness exhibits shear failure. With the increase of the normal stress, the failure mode of the specimen containing only waviness changes from slip failure to shear failure; (2) the unevenness controls the damage degree of the joint specimen. The damaged area, damage volume, AE energy rate, and accumulative AE energy of the joint specimen with unevenness are larger than those of the specimen with only waviness, and this difference increases with the normal stress increase; (3) the difference between the joint specimen with unevenness and specimen with only waviness mainly exists in the prepeak nonlinear stage and the postpeak softening stage. The characteristic parameters of acoustic emission generated in the postpeak softening stage of the joint specimen with unevenness are greater than those of the specimen with only waviness. This phenomenon can be used to explain the stress drop difference at the postpeak softening stage; (4) the AE b value can be used to evaluate the damage of joint specimens. Analysing the damage difference of each asperity order under different normal stresses is of great significance to the analysis of the influence of the morphology of the joint surface on the mechanical properties of the joint.

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Experimental Investigation of Anisotropic Wear Damage for Natural Joints under Direct Shearing Test

Cited by 27 publications

References 50 publications

Roughness Evaluation for Distinguishing Fresh and Sheared Rock Joint Surfaces with Different Sampling Intervals

Roughness Evaluation for Distinguishing Fresh and Sheared Rock Joint Surfaces with Different Sampling Intervals

A New Characterization Method for Rock Joint Roughness Considering the Mechanical Contribution of Each Asperity Order

Exploring the Effect of Asperity Order on Mechanical Character of Joint Specimen from the Perspective of Damage

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