The use of pore pressure reinflation testing in landslide management in Hong Kong

Risk management for natural terrain landslides requires understanding of the complex underlying processes during the development of failure. This paper utilizes a process approach based upon triaxial testing using the field stress path to examine the effect of the rate of stress changes in a landslide system by analysing the pre-failure movements of undisturbed soil materials collected from Hong Kong using inverse velocity-time techniques. The results provide enhanced understanding of the deformation mechanisms, showing that rainfall-induced landslide development on weathered slopes undergoes three distinctive movement patterns during the development of failure. Initially strain accumulation occurs at very low rates (Stage 1). This is followed by a stage of fluctuating strain rates (Stage 2), and finally by rapid acceleration (Stage 3). The results emphasize that although the deformation of residual soils is dependent upon the stress state of the material, there is also a strong time-dependent element of the failure process.