The basic friction angle is a basic parameter used in the shear strength estimation of discontinuities. The accurate determination of the shear strength of the discontinuities is of great importance for engineering structures built on or inside the rock.
In this study; the variation of the basic friction angle tests under dry and different fluid conditions were carried out. For this purpose, a tilt device was designed. 7 different types of travertine samples with dimensions of 10x10x2 cm were used in the experiments. Tilt tests; to determine the change of the basic friction angle under different liquid conditions, dry, pH2, pH7 and pH12 were carried out under different test fluid conditions. Basic friction angles were measured 5 times in each group experiment. Initial basic friction angles were high regardless of sample type and experimental conditions. But; as the measurements continued, significant changes were observed about slip angles. The lowest basic friction angle was obtained in samples conditioned with pH2 while the highest angle was obtained in samples with ph7 conditioned. Thus, the effect of different water contents on sliding surfaces was determined experimentally. It is thought that this study can contribute to the existing studies on the basic friction angle with the tilt test.
The engineering properties of rock masses are greatly influenced by the sliding behaviour of joints. The main factors affecting the shear strength of an unfilled joint are rock, roughness, size of the joint, the degree of weathering, the strength of the joint surfaces, moisture and water pressure [1]. Discontinuities in rock masses are generally rough. Rough joints without natural filling’s peak strength behaviour is expressed as follows [2].
(equation)
τ shear strength of the joint, σn normal stress applied to the joint, φr residual friction angle, JRC the joint roughness coefficient, JCS the compressive strength of the joint surface. The residual friction angle, φr is estimated according to Barton and Choubey [3] as follows:
(equation)
φb is the basic friction angle, r is the Schmidt hammer rebound number recorded for a weathered and wet discontinuity, such as those normally found in the field, and R is the Schmidt hammer rebound number recorded for the unweathering surfaces of the same rock.