cofferdam

1. N a watertight structure, usually of sheet piling, that encloses an area under water, pumped dry to enable construction work to be carried out. Below a certain depth a caisson is required 圍堰; 一種防水建筑物，通常由鋼板樁筑成防水層，將水下某一區(qū)域圍住，并將結(jié)構(gòu)內(nèi)水排干以便可以施工，在水下一定深度時(shí)，需要佩戴潛水箱