Natural experiments in rock mechanics using high precision monitoring of chalk sea cliffs

Prediction of rock slide events remains a difficult task for geoscientists. Kinematic analysis provides an indication of possible modes of failure at a site. However, the highly variable nature of chalk compressive strength due to variations in water content and salt weathering is such that parameterizing models of slope stability can result in large variations in the resultant factor of safety. In this work, we use high-precision monitoring data of an eroding coastal cliff to characterize the geometry of a large wedge failure in chalk. We use these data in conjunction with published material properties to model the joint compressive strength of the chalk at the time of failure through back analysis. Results indicate a strength of 7.19 KPa for the chalk suggesting that the joint surface was close to saturation at the time of failure.