Evidence of overpressure at the base of huge landslide

Abstract

Overpressuring from generation of CO2 gas caused by thermal decomposition of basal carbonates can raise pore-fluid pressure and reduce friction during landsliding. We used thermogravimetry and dilatometry to determine the evidence of raised pore-fluid pressure from carbonate thermal decomposition at the base of the 2009 Jiweishan landslide. Results from thermal expansion experiments showed that the rock undergoes expansion and thermal fracture. At a heating rate of 20°C/min, the coefficient of linear thermal expansion increased sharply at 807.3 °C and reached a maximum of 36.6×10−6 °C −1 at 827.3 °C. DTG data show that the temperature of the maximum thermal decomposition rate of calcite is 852.5°C. The evidence showed that CO2 gas can produce great pressure during the rapid sliding process of Jiweishan landslide, and it is conducive to reduce the effective normal load. In addition, thermal fracture may be a explanation for the ultra-low friction during the rapid sliding by reducing the strength of the rock at the sliding surface and making it more easily entrained.