Shear Behaviour of Rock Joints Under CNL and CNS Boundary Conditions

Abstract

Shear behaviour of rock joints can be studied under both constant normal load (CNL) and constant normal stiffness (CNS) boundary condition. CNS condition is suitable for non planar and reinforced rock joints whereas CNL condition is suitable for planar and non reinforced rock joints. In the present study shear behaviour of modelled rock joints with different asperity have been experimentally investigated under both CNL and CNS boundary conditions. Test results indicate that CNS boundary conditions gives higher shear strength as compare to CNL boundary condition when other parameter of testing is kept same. But, this effect tends to diminishes with increase in normal stress on the shearing plane and at high normal stress both CNL and CNS boundary conditions gives same shear strength. A new shear strength model is proposed for both the boundary condition and the proposed model is validated by comparing the predicted shear strength with present experimental results and results available in the literature for natural and artificial rock joints with different asperity and roughness. The new study and model will be useful for safe and economical design of underground openings in jointed rocks, stability analysis of rock slopes, design of foundation on rock and design of rock socketed piles.

Experimental Investigation of the Permeability Measurement of Radial Flow through a Single Rough Fracture under Shearing Action

“…e boundary condition of this direct shear test was CNL, which is mainly used for rock slope stability analysis [25,26]. Barton pointed out that when engineering problems related to a rock mass occur, the effective normal stress is commonly between 0.1 MPa and 2.0 MPa [27].…”

Three-Dimensional Combined Finite-Discrete Element Modeling of Shear Fracture Process in Direct Shearing of Rough Concrete–Rock Joints

“…The problem of the failure of the concrete-rock (C-R) joint under shearing has been considered as a special case of the failure of rock mass containing rough joint surfaces (i.e., rock-rock joint) under shearing. The problem of rock-rock (R-R) joints subjected to shearing has been investigated extensively, and several models for this problem have been proposed [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. These studies have examined the major factors that affect the behavior of the R-R joint, considering the rock mass properties around the rock joint, joint surface roughness, and boundary conditions applicable to joints, and some useful solutions have been proposed.…”

Hybrid finite-discrete element modelling of asperity degradation and gouge grinding during direct shearing of rough rock joints

“…Maksimovic (1996) proposed a non-linear joint failure model of hyperbolic type with three parameters: the basic angle of friction, the roughness angle and the median angle pressure. More recently, many joint constitutive models have been developed for the physical-mechanical behaviour of rock joints (Indraratna and Haque 2000;Olsson and Barton 2001;Seidel and Haberfield 2002;Serrano et al 2014;Indraratna et al 2015;Hencher and Richards 2015;Shrivastava and Rao 2015). However, these constitutive models have difficulty in implementing the real geometry of rock joints and the input parameters of these models are predefined by the user, which hampers the predictive capability of these models (Bahaaddini et al 2015).…”