Evaluation and monitoring of man-made slope failure at Øysand, Norway

Abstract

The road and railways infrastructure developments in Norway have increased the interest in the geotechnical challenges associated with slope stability under freezing-thawing cycles. In this case study, a critical slope was identified in a cold region based on field site investigation and frost-heave laboratory tests, and a series of numerical simulations were carried out before creating a man-made slope at Øysand, Norway. A remote monitoring system was installed on the large scaled man-made slope to observe its behavior against the governing factors of slope stability. It was noted that slope stability was slightly impacted by the freezing– thawing action, which was monitored by the initial field observations from November 2019 to March 2020. The slope failed in April 2020 after a heavy precipitation event. Back-calculations of the slope stability were performed to find out the main reason for the slope failure. It was found that the most likely reason was heavy rainfall with intensity over 5 mm/hr, inducing the flux of water through the tension cracks, increasing pore water pressure, and decreasing the matric suction, which resulted in reduction of shear strength and failure of the man-made slope. The slope was minorly impacted by the freezing-thawing action during the observation period.