INFLUENCE OF INFILLING ON THE STRENGTH BEHAVIOUR OF ROCK JOINTS

Abstract

Determination of shear strength of infilled discontinuities is perhaps one of the complex problems faced by geotechnical engineers. The main difficulty is due to the increased number of variable parameters which influence the shear strength of infilled jointed rock masses. In the present work, the results of a series of direct shear tests conducted at strain rates (0.125 mm/r and 0.625 mmA,(f-1) on models of cement discontinuities of different asperity angles (150, 300, and 450) and of mean roughness amplitude 4mm filled with different thickness of china clay and flyash are reported. It is shown that peak shear strength decreases with increasing fill thickness (t) and approaches a minimum when t/a (thickness-amplitude ratio) is between 1.8 and 2.5, indicating the influence of normal stresses and asperity angle of discontinuity. The results revealed drop in shear strength with decreasing roughness. Effect of strain rates on shear strength was also. found. Finally the expressions for prediction of peak friction coefficients for a filled discontinuity proposed by Papaliangas et.al. (1993) is verified...