SLOPE STABILITY PROBLEMS AND THEIR MITIGATION DURING CONSTRUCTION OF THE EDEN PROJECT IN A WORKED-OUT CHINA CLAY QUARRY IN SOUTH-WEST ENGLAND

摘要

The Eden Project - a new botanic garden and scientific institute - is being created in a 15ha, 50m deep abandoned kaolin quarry at Bodelva in Cornwall, south-west England. It is located in the historic kaolin mining area around St. Austell, Cornwall. Within the quarry the world's two largest plant conservatories (or biomes) are being constructed. The economically important China clay, or kaolin, is a weathering product of the feldspars found in the granite of the region and is hydraulically mined in open pits. The geology of the quarry is dominated by biotite granite in various stages of weathering. The granite of the pit interior was classified into four grades according to the degree of weathering and kaolinisation. The degree of kaolinisation has a profound effect on slope stability and. The choice of remediation method. Other factors affecting the geotechnical characteristics of the pit include hydrogeological features such as surface streams and groundwater issues. The appropriate mitigation of slope stability problems was imperative for the safe construction and subsequent management of the biomes and the Eden Project. The floor of the pit was raised by 20 m prior to construction, thereby incorporating settlement and potential subsidence as important considerations. Mining activities also released hydrostatic pressure in certain areas further affecting the pit's geotechnical characteristics. This paper reviews the geotechnical investigations undertaken in the Eden Project's quarry, including aspects of slope stability, hydrogeology and ground investigations and, where appropriate, discuss the methods of reclamation used to produce a geotechnically benign environment for the development of a major visitor attraction.