Suction controlled stability [Hong Kong]

The question of the contribution of negative pore pressures to slope stability can be addressed using CHASM™ since the model incorporates dynamic unsaturated and saturated soil water conditions. Indeed the basis for the development of CHASM™ was just such a question in the context of Hong Kong slopes, and particularly those of the Mid-Levels area, Hong Kong.

Mid-levels area, Hong Kong

Whilst CHASM™ was used to address this question on natural slopes, the effect of surface cover in maintaining or indeed eliminating negative pore pressures can be investigated. In areas such as Hong Kong surface cover ranges from grasses to gunite [or chunam - a concrete mix]. Gunite is intended to reduce the immediate soil surface infiltration to zero and has been widely applied in high density urban areas, as well as on certain highway.

Application of gunite to prevent infiltration

See weblink to GCO Publication No. 1/84:
http://www.ced.gov.hk/eng/publications/geo/georpt_f.htm

Report abstract: It aims to determine the effect of different surface coverings upon the soil suction regime of the underlying slopes, to evaluate the relative importance of slope matnerial and topography in controlling suction, to examine and develop a prediction model for soil suction, and to review current soil suction instrumentation capabilities and assess the need for further development in the context of requirement for Hong Kong.