PORE PRESSURE MONITORING WITHIN THE FOUNDATION AND IMPERVIOUS ZONE OF KARKHEH DAM DURING CONSTRUCTION

摘要

Karkheh Dam, a 127 m high earth-rock fill dam with the crest length of 3 030 m, is the largest dam under construction in Iran and Middle East. The dam is located on the Karkheh River at southern west of Iran and founded on a sequence of conglomerates separated by inter-layers of mudstones. The mudstones are deposited in near horizontal direction at different elevations. This paper describes the instrumentation installed in the dam body and its foundation to measure the water pressure. The continuity and the extent of these layers (especially upstream of the dam) were the paramount design information. Appropriate selection of the dimension (mainly depth) of the plastic concrete cut-off wall (chosen as the main anti-seepage measure) in relation to the extent of the mudstones was also an important design decision. The usual conventional methods (boring and geophysics, etc) were employed to assess the extent and continuity of mudstone, but due to the variety and complexity of the foundation i.e. the conglomerate, the methods were not successful.