Abstract Rock joint roughness coefficient (JRC) is an important parameter to determine the shear strength of unfilled hard rock joints. It is of great significance to acquire a representative value of JRC. For irregular undulated joints, the JRC has a strong directivity and surface inclination can reflect the roughness difference under the condition of cyclic shear. Considering Barton's standard joint roughness profiles as an example, the secant angles and tangent angles of surfaces dipping opposite to shear direction were calculated and then the mathematical relationships with JRC were investigated. Based on the results of the study, it can be said that all mathematical relationships of surface inclination of surfaces dipping opposite to shear direction with JRC satisfy the power law equations. The average value of entire secant angles of all surfaces dipping opposite to shear direction ( β 100% ) has a higher sensitivity to evaluate JRC comparing with other parameters. It ( β 100% ) is recommended as a new index to describe JRC considering the directivity. Under cyclic shear, it shows that the JRC of forward positive shear process (JRC fp ) is basically larger than that of backward positive shear process (JRC bp ) except the first and the fifth standard profile. Moreover, the JRC bp value of the seventh standard profile is smaller than that of the fifth and sixth one. With the digitized sampling interval increasing, the correlation coefficient of the relationships between β 100% and α 100% (average value of entire tangent angles of surfaces dipping opposite to shear direction) and JRC of Barton standard profiles both present a trend of decreasing and the former is a little larger than the latter under the condition of equal sampling interval.

Abstract In this paper, the shear behaviour and mechanisms of asperity degradation of rock joints under direct shear tests were studied using numerical and experimental approaches. PFC2D was used for numerical simulations, in which the intact material is simulated by a dense packing of circular particles bonded together at their contact points and by breakage of these bonds under loading regimes, the damage process is simulated. The joint interfaces were simulated by a newly developed modified s...

The joint roughness coefficient (JRC) of rock joints has the characteristic of scale effect. JRC measured on small-size exposed rock joints should be evaluated by JRC scale effect in order to obtain the JRC of actual-scale rock joints, since field rock joints are hardly fully exposed or well saved. Based on the validity analysis of JRC scale effect, concepts of rate of JRC scale effect and effective length of JRC scale effect were proposed. Then, a graphic method for determination of the effecti...

#1Songfeng Guo(CAS: Chinese Academy of Sciences)H-Index: 6

#2Shengwen Qi(CAS: Chinese Academy of Sciences)H-Index: 14

Abstract Roughness is one of the most important parameters of unfilled joint. In this study, a series of numerical tests have been carried out on the progressive failure of rock masses with varied undulate joints. The numerical model reproduced the stress–strain relations obtained in lab tests on the marble samples with smooth joint under the confinement of σ 3 /σ c = 0.013 and 0.27; meanwhile, the results of the numerical model on rock mass with rough joint indicated that with the increase of c...

#1Yanrong Li(TUT: Taiyuan University of Technology)H-Index: 19

#2Yongbo Zhang(TUT: Taiyuan University of Technology)H-Index: 6

where τ is the peak shear strength of the rock joint, σ is the normal stress, JRC is the joint roughness coefficient, JCS is the strength of joint wall, φb is the basic friction angle. Over the last half century, researchers have kept working on techniques for estimating JRC of rock joints for or from this model. So far, the JRC value of a particular rock joint is most often estimated by visibly comparing it to the ten standard profiles with JRC values ranging from 0 to 20 [2]. This method was a...

#1Yanrong Li(TUT: Taiyuan University of Technology)H-Index: 19

Abstract Numerous empirical equations have been proposed to estimate the joint roughness coefficient ( JRC ) of a rock fracture based on its fractal dimension ( D ). A detailed review is made on these various methods, along with a discussion about their usability and limitations. It is found that great variation exists among the previously proposed equations. This is partially because of the limited number of data points used to derive these equations, and partially because of the inconsistency ...

Last. Bo-An Jang(Kangwon National University)H-Index: 4

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This study used precisely digitized standard roughness profiles to determine roughness parameters such as statistical and 2D discontinuity roughness, and fractal dimensions. Our methods were based on the relationship between the joint roughness coefficient (JRC) values and roughness parameters calculated using power law equations. Statistical and 2D roughness parameters, and fractal dimensions correlated well with JRC values, and had correlation coefficients of over 0.96. However, all of these r...

#1Zhu Xiao-Ming(CAS: Chinese Academy of Sciences)H-Index: 4

Using cement mortar as similar material,joint specimens with three joint wall strengths and five asperity angles were prepared.Then a series of cyclic shear tests are performed at four normal stresses on the cyclic shear test apparatus.Tests results show that,shear stress-shear displacement curve has peak strength of each shear cycle,and the shear strength of joints gradually decrease with the cyclic number increase.The peak shear strength of joint after n cycles is expressed as,then the = / is ...

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 ...

In this study, a series of artificial rock joint specimens were subjected to a pre-peak cyclic loading test. The effects of the initial joint roughness parameters (Z2(initial)), joint wall compressive strength (JCS), normal stress during cycle (σnc), cycle frequency (f), cycle amplitude (A), and cycle number (N) on the mechanical behaviors and asperity degradation were studied extensively. The results revealed that the joint surface degradation coefficient Rd and the joint surface degradation th...

The surface morphology of joints directly determines the contact area and peak shear strength of rock in shearing. This research gives a detailed description of the three-dimensional roughness parameters proposed by Grasselli, and discusses the morphology characteristics of the roughness parameter C in different ranges. Quoting Xia's direct shear test data, the relationship of peak shear strength, peak shear strength/normal stress, residual strength, dilation with roughness and normal stress are...

The 10 standard roughness joint profiles provided a visual comparison to get the joint roughness coefficient (JRC) of rock joint surface, but the accuracy of this method is influenced by human factors. Therefore, many researchers try to evaluate the roughness morphology of joint surface through the statistical parameter method. However, JRC obtained from most of the existing statistical parameters did not reflect the directional property of joint surface. Considering the 10 standard profiles as ...

The mechanical properties of joints are important factors affecting the safety and stability of rock mass. The joint roughness coefficient (JRC) is a parameter for describing the roughness morphology of the joint surface, and its accurate quantification is very important to predict the shear strength. In the current statistical parameter methods for the estimation of joint roughness, the size of different protrusions on the joint surface was completely ignored, which did not correspond to the re...

#1Bowen Zheng(CAS: Chinese Academy of Sciences)H-Index: 5

#2Shengwen Qi(CAS: Chinese Academy of Sciences)H-Index: 14

Last. Songfeng Guo(CAS: Chinese Academy of Sciences)H-Index: 6

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The fractal geometry method has been employed to quantitatively characterize the roughness of a rock discontinuity, which is one of the key factors affecting its shear strength and the seepage characteristics of a rock mass. However, the current fractal methods involving the three-dimensional discontinuity morphology suffer from one or more problems, such as a complicated calculation procedure, an inaccurate calculation result and an inability to characterize the undulation and anisotropy of a d...

Last. Yucong Pan(WHU: Wuhan University)H-Index: 11

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Joint roughness significantly affects the damage areas and peak shear strength of the rock joint. In this study, theoretical analysis and numerical simulations were carried out, and the results indicated that the resistance angles and heights of asperities quantified the damage range and damage degree, respectively, during the shearing process. Direct shear tests and 3D scanning tests were conducted on sets of mortar joint replicas and sandstone joints. By analyzing the test data, several morpho...

#1Xiaolin Huang(CAS: Chinese Academy of Sciences)H-Index: 27

#2Shengwen Qi(CAS: Chinese Academy of Sciences)H-Index: 14

Last. Daping Tai(CAS: Chinese Academy of Sciences)

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Abstract Laboratory tests revealed that by enhancing the weathering degree, a transition of pre-peak stress-strain mechanical responses of crystalline rocks under unconfined compression from approximate linearity to nonlinearity was evident, as was the weakening of macro-mechanical properties. However, thus far, very few numerical studies have been conducted to quantitatively characterize the strong-to-weak transition of the mechanical behaviors of crystalline rocks modulated by the weathering d...

Last. Chengzhi Qi(Beijing University of Civil Engineering and Architecture)H-Index: 1

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Abstract Based on the index, the root mean square of the first derivative of the profile (Z2), the contribution of the asperities with different geometric characteristics to the peak shear strength (PSS) is considered, and an improved roughness index (Z2)ds is proposed. (Z2)ds is reasonably related to the PSS and can reflect the directionality of the PSS. The direct shear tests of 60 joints under different normal stress are carried out. Test results show that the PSS is related to normal stress,...