Large-scale Geotechnical Hazards Caused by Environmental Actions: Impact of Rainfall and Reservoir Filling (Sponsor: NSFC-RGC; PI: Prof. Zhang LM; Co-Is: Prof. Fredlund, DG, Prof. Tang, WH and Prof. Tung, YK; Researchers: Dr Chen Q., Mr. LI Xu, Miss LI Jinhui, Dr Wu Lizhou and Mr. Liu Wenping)

This research project focuses on geo-hazards in natural terrains caused by two environmental actions, namely, fluctuations in man-made reservoir water levels and rainfall infiltration.  Steep terrains and frequently occurring tropical rainstorms often cause landslides on natural terrains.   A typical example is the failure of colluvial gap-graded soil deposits commonly seen in Hong Kong.  More than 25,000 visible natural terrain landslides have been identified in Hong Kong.  In mainland China, as many as 684 individual slopes larger than 100,000 m³ and numerous smaller slopes have been identified in the Three-Gorge Reservoir Zone (TGRZ).  These slopes will be partially submerged by the reservoir after June 2003.  Failure of some of these slopes in the TGRZ could be activated by reservoir water infiltration to the slope material, drawdown of the reservoir level, rainstorms, or combinations of the above.  The pressing issue of reservoir slope instability, however, has not been sufficiently studied.  The major objectives of this research project are to (1) investigate the fundamental processes of water flow through unsaturated gap-graded soils; (2) to evaluate the stability of natural terrain soil slopes in response to the transient flows and hydrodynamic forces resulting from a combination of rainstorms and reservoir level changes; and (3) to synthesize, in a systematic manner, the experience gained from a large-scale slope stabilization programme against water environmental actions, which is being implemented in the TGRZ.