Influence of Freeze-Thaw on the Stability of Road Cut Slopes near Atal Tunnel in Indian Himalayan Region

Abstract

The rock slopes in the Indian Himalayan region are exposed to recurrent freeze-thaw. Freeze-thaw plays a dominant role in the instability of rock slopes in cold regions. Extensive field investigations have been carried on the two rock slopes of the Solang valley roadway in Himachal Pradesh. Freeze-thaw testing has been carried out in the laboratory on the rock samples collected from the studied slopes. The test has been repeated for 30 freeze-thaw cycles. The laboratory tests have been conducted to determine the mechanical properties of rock with and without freeze-thaw conditioning. The micro-photographs from scanning electron microscope have been obtained to identify the microscopic damages due to freeze-thaw activity. The macroscopic damages have been recognized in tensile, compressive and triaxial compressive strength of rock. Further, a three-dimensional numerical analysis has been performed to evaluate the stability and corroborate the results with the field observations. FT conditioning results reveal a reduction of about 27–39 % in rock strength and subsequently a decrease in the factor of safety by 10–39 % for rock slopes.