Study on Application of CSG Cofferdam in Hydropower Station Construction

CSG method is a new technique proposed for RCC; the key of this technique is the application of CSG (cement sand and gravel) to dam construction. CSG is a material, which can be considered as a lean RCC, made by adding a little amount of cement to rock-like material such as riverbed gravel or excavation muck that can be obtained easily from dam sites, then mixing it briefly with simple equipments and rolling with vibration rollers. CSG dam is a symmetrical trapezoid-shaped dam; the strength of CSG is relatively weak compare to concrete. On the other hand, because the stress occurred in a symmetrical trapezoid-shaped dam is small; the required strength of its material can be low. Therefore, the CSG can be used to construct trapezoid-shaped dam. It has been proved by practice that CSG dam has the advantages of greater safety, shorter construction period, lower construction costs and better performance on environmental protection, so it attracts more and more attention in Europe and Japan currently. The upstream CSG cofferdam in Daotang dam project is the first time for China to put this technique into practice. This article introduces the design, construction and structural analysis of the CSG cofferdam in Daotang dam, and clarifies the characteristics of CSG method and the advantages of this method for temporary structure such as cofferdam. Based on the results of material test and site rolling experiments, the characteristics of CSG material and some useful technical parameters of CSG method are gotten. All these are accumulated experience for the application of the CSG method in China.