Utilization of Weathered Rock Mass as the China Three Gorges Dam Foundation

The utilization of the weathered rock mass in the Three Gorges Dam Area is one of the key geotechnical issues for the China Three Gorges project (CTGP) construction. Engineering geological investigations and tests had been carried out to study the physical, chemical, mineral and mechanical properties and distribution characteristics in detail for more than 30 years. The classification of the weathered zone has been further divided. The utilization of the lower part of the weakly weathered zone as the Three Gorges dam foundation rock mass had been researched by consolidation grouting test. The research results show that: (1) The weathered rock mass in Three Gorges dam area has a great thickness of 40–70 m, with inhomogeneous behavior, physical and mechanical properties in different weathering zones. (2) It is feasible that the lower part of the weakly weathered zone could be used as the dam foundation after consolidation grouting treatment. This approach can save a large amount of construction investment. (3) The weathered rock mass can be used as different civil engineering foundation, and different weathered zone can satisfy different foundation bearing layer requirements. (4) The weathered rock mass can be utilized as construction material. The completely-weathered rock mass can be used as cofferdam filling sand material. The weakly and slightly weathered granite can be used as filling rock materials of cofferdams.