Thermo-mechanical cliff stability at tomb KV42 in the Valley of the Kings, Egypt

Abstract

The Valley of the Kings (or Kings' Valley, KV) in Egypt is surrounded by tall, subvertical cliffs of marl and limestones which are close to archaeological sites and visitor pathways. A previous analysis of the slope above the KV42 tomb entrance suggested that vertical rock discontinuities (i.e., tectonic joints and a lateral tension crack) have a large impact on the stability of the cliffs. The site at KV42 is being monitored with a weather station, a crack meter and a seismometer. Preliminary data analysis of temperature and relative humidity cycles suggests a correlation with cyclic crack aperture changes of a prominent tension crack in the cliffs above KV42. Weather data from April 2018 to present help in understanding the environmental conditions of the site. During a field campaign in April 2019, an infrared sensor was installed to systematically capture thermal infrared images of the slope above KV42, and therefore to observe the thermal response of the rock slope to correlate with the environmental conditions and the geomechanical response of the rock mass. The sensors were used to delineate the thermal boundary conditions of the slope allowing for the thermo-mechanical response of the rock mass under fluctuating environmental conditions to be numerically modelled in FLAC®. Results showed that peak values of total displacements have a delay with respect to peak values of temperatures, similar to that observed in the real measurements. Modelled rock temperatures are higher than measured data, 3% in warm months and 68% in cooler periods. The total displacement trend is similar to measured data, however the model underestimates the peak displacement by 0.2 mm. The research forms the basis of an approach to incorporate weather conditions into long-term stability modelling of rock mass.