A new shear strength model incorporating influence of infill materials for rock joints

• DOI: 10.1007/s40948-016-0032-4
• Publication Date: 2016-07-15T15:26:45Z
• Authors: Murat Karakus; Yi Liu; Guangcheng Zhang; Huiming Tang
• Keywords: Particle flow codes; 690; infill; joint roughness coefficient (JRC); shear strength degradation; 01 natural sciences; 0105 earth and related environmental sciences

Overall mechanical behaviour of jointed rock masses is predominantly controlled by the shear strength of rock joints which contain infill materials. Barton’s empirical model has been shown to be one of the most successful model in predicting joint shear strength (Barton and Choubey in Rock Mech 10:1–54, 1977). However, the Barton model does not express the effect of infill material explicitly, but only incorporates influence of infill into the factors of joint-wall compressive strength (JCS) and residual friction angle. Although there are a large number of studies carried out on the effects of infill materials on the shear strength of rock joints, none of them incorporated infill influence directly into the Barton’s formulation. This paper investigates the effect of infill thickness on JCS and the overall joint shear strength. The interface between wall rock and infill material thicknesses ranging from 1 to 5 mm is simulated by using smooth-joint model. A natural joint is digitally scanned and the roughness geometry is used in all PFC3D models. The results showed that JCS does not show a significant variation at high infill thickness up to a threshold limit of 2 mm. However, JCS decreases drastically at low infill thickness. As expected the shear strength of filled joints reduces from fresh joints to the infill materials, as the infill thickness increases. The reduction is inversely related to the infill thickness. The reduction factor k has a negative exponential relation with the normal stress, indicating that the effect of infill material is stronger at lower normal stress while effect of joint roughness is stronger at higher normal stress.