Experimental Study on Peak Shear Strength Criterion for Rock Joints

Abstract

The three-dimensional (3D) morphology of a rock joint has a great impact on its shear behavior. To study the relationship between the 3D morphological characteristics and the peak shear strength, several tilt tests were conducted on four groups of tensile fractures and direct shear tests were carried out under different constant normal loads (CNL). The normal load ranges from 0.325 to 8.0 MPa. In this study, fresh tensile fractures which were splitted from granite and sandstone samples were used. The morphology of each tensile fracture was measured before direct shear tests. A new peak shear strength criterion for rock joints is proposed using two 3D morphological parameters which are termed as the maximum apparent dip angle h à max and the roughness parameter C. The calculated peak strengths using the proposed criterion match well with the observed values. In addition, a comparison of the proposed model with the Grasselli's model (2003) and Xia's model (2014) shows that the proposed model is easier in the form and gives a rational improvement. At last, direct shear test data of tensile fractures which are collected from Grasselli (2003) are used to verify the proposed model. It is seen that the proposed model has a reliable estimate of the peak shear strength of tensile fractures and presumably for rock joints.

Novel Intelligent Approach for Peak Shear Strength Assessment of Rock Joints on the Basis of the Relevance Vector Machine

“…e values of A 0 and θ * max /(C + 1) are listed in Table 3. Figure 3 shows the fitting curves of SJ3, SJ12, SJ21, and SJ36 for calculating the roughness parameter C. Joint wall compressive strength (JCS) is commonly used for representing the influence of rock material strength on the shear behavior of rock joints [3,8,25,[39][40][41]. For the fresh rock, JCS can be replaced by the uniaxial compressive strength σ c .…”

“…erefore, the accurate determination of shear strength is the key to design the safety structure in rock mass or rock masses [1]. Over the past decades, empirical [2][3][4][5][6][7][8][9], semi-theoretical [10], and theoretical methods [11] have been proposed to determine the shear strength of rock joints. Various factors, such as rock type, joint surface roughness, joint size, and infilling materials, exhibit a wide variation of joint shear strength [12,13].…”

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

“…With regard to shear behavior evaluation through laboratory investigation, the direct shear test and cyclic shear test have gained significant attention. Considering the spatial geometry and stress state of rock joints, direct shear tests [6,[16][17][18][19][20] and cyclic shear tests [7,8,[21][22][23][24][25] were conducted by different researchers from around the world. It should, however, be noted that the aforementioned shear test requires a costly shear test apparatus, and moreover, it involves a difficult, complex, and time-consuming procedure of sample collection and preparation.…”

Influence of Structural Plane Microscopic Parameters on Direct Shear Strength

“…Many scholars have conducted relevant research [6][7][8][9][10][11][12]. Yang et al [13] study the relationship between the 3D morphological characteristics and the peak shear strength through several tilt tests. Fardin et al [14] carried out investigations to understand the effect of scale on the surface roughness of rock joints.…”