A study on the shear behaviour of infilled rock joints under cyclic loading and constant normal stiffness conditions

Shear behaviour of infilled rock joints under cyclic loading and constant normal stiffness conditions were studied. The experiments were carried out in a cyclic loading direct shear apparatus. The laboratory studies were conducted using saw tooth shaped asperities cast in high strength gypsum plaster. Two types of triangular asperities inclined at 9.5° (Type I) and 18.5° (Type II) from the shearing direction were considered for testing. Clayey sand (75% fine sand and 25% Kaolinite) at initial moisture content of 12.5% was selected as the infill material. Profile of shear planes and strength envelopes for different conditions of infill thickness to asperity height ratio, initial normal stress, and initial asperity angle were investigated.