Underwater coffer dam construction using preplaced aggregate concrete

摘要

The sandstone mass rock in front of spillway bucket of a 60-m high dam constructed in the early 1960s experienced serious erosion in view of the continuous scouring action of flowing water. The erosion of rock mass, which was about 3-10m deep, posed serious threat to the safety of the dam. It was therefore proposed to construct a 1.5-m thick reinforced concrete raft immediately downstream of the spillway bucket and tie the same to the bed rock using 10-m long passive anchors. However, in view of the 10-m deep pool of standing water, it was found essential to construct an underwater coffer dam using preplaced aggregate concrete (colcrete). The paper describes the salient features of the construction of coffer dam, raft and passive anchors.