Strength and dilatancy of jointed rocks with granular fill

Abstract

It is well recognised that the strength of rock masses depends upon the strain history, extent of discontinuities, orientation of plane of weakness, condition of joints, fill material in closely packed joints and extent of confinement. Several solutions are available for strength of jointed rock mass with a set of discontinuities. There is a great multiplicity in the proposed relationships for the strength of jointed rocks. In the present study, the author conceives the effect of increasing stresses to induce permanent strains. This permanent strain appears as micro crack, macro crack and fracture. A fully developed network of permanent deformations forms joint. The joint may contain deposits of hydraulic and hydrothermal origin commonly known as gouge. The joint factor numerically captures varied engineering possibilities of joints in a rock mass. The joints grow as an effect of loading. The growth of the joints is progressive in nature. It increases the joint factor, which modifies the failure stresses. The dilatancy explains the progressive failure of granular media. Hence, a mutual relationship conjoins effectively the strength of jointed rock and a dilatancy-dependent parameter known as relative dilatancy. This study provides a simple and integral solution for strength of jointed rocks, interpreted in relation to the commonly used soil, and rock parameters, used for a realistic design of structure on rock masses. It has scope for prediction of an equivalent strength for triaxial and plane strain conditions for unconfined and confined rock masses using a simple technique.

Computing in-situ strength of rock masses based upon RQD and modified joint factor: Using pressure and damage sensitive constitutive relationship

“…According to Arora (1987) and Ramamurthy and Arora (1994), the joint set is multiplicatively equivalent to joint factor (J f ). According to Trivedi (2010), a modified joint factor (J fg ) was proposed to capture the multiplicative equivalence of all the rock and gouge parameters and their transition as the loading proceeds. Arora (1987) and Trivedi (1990) obtained the orientation parameter for the blank and gouged joints as shown in Table 6.…”

“…The reference value of friction parameter r ¼ 1, and the reference value of length parameter L a ¼ 1 m. Based upon the experimental results of several investigators (Yaji, 1984;Arora, 1987;Trivedi, 1990;Arora and Trivedi, 1992;Trivedi and Arora, 2007;Trivedi, 2010Trivedi, , 2013a, the author considered varied engineering parameters of rock masses from laboratory tests in relation to field investigations to define c g as…”

“…Additionally, RMR and GSI present a measure of qualitative assessment of jointed rock masses. The Q-system (Barton, 1986(Barton, , 2013 considered six parameters including RQD, joint number, roughness, effect of Trivedi et al (2015), g Trivedi (2010Trivedi ( , 2013a.…”

“…McLamore and Gray (1967) pointed out the significant effect of the joint inclination on the strength of jointed rocks at low confinement. Ramamurthy and Arora (1994) and Trivedi (2010) considered joint parameters consisting of joint number, orientation, roughness and block to propose the strength of jointed rock mass based on statistical and numerical analysis, respectively. Priest and Hudson (1976) and Sen (1984) proposed a relationship between discontinuity spacing and RQD to capture insitu state of rock quality designated on a broad scale.…”

Investigation of Dilatancy Effects on Asphalt Interface Shear Strength

“…On the other hand, when distortion and volumetric strain occur during shear, as in Fig. 1b, ψ is a function of plastic shear strain and plastic volumetric strain (Trivedi 2010).…”