Thermally vs. seismically induced block displacements in jointed rock slopes

Abstract

We explore two landslide triggering mechanisms that are associated with time dependent, cyclic loading of the sliding interface. The first is shear strength degradation due to seismic shaking leading to velocity weakening of the sliding interface. We show how a block that is initially at a state of static limit equilibrium under constant gravitational load may undergo sliding at increasing velocities when subjected to cyclic vibrations and demonstrate, using shaking table experiments, how the observed shear strength degradation may lead to block run out. The second is sliding initiation due to cycles of seasonal heating and cooling of the jointed rock mass. We demonstrate, using field measurements, analytical and numerical approaches, how repeated cycles of heating and cooling may trigger block sliding along an inclined sliding plane via a thermally induced ratcheting mechanics in the sub vertical tension crack. We show that for Masada rock mass the thermal mechanism may lead to a faster sliding rate than the seismic mechanism for a given regional seismicity and climatic conditions for a time window of 5000 years when the shear strength of the sliding plane is considered constant over time. We therefore conclude that thermally induced sliding must be considered when studying the stability of rock slopes that are exposed to strong temperature changes between the seasons.