在水中修建桥梁墩台基础时,不仅要防止坑壁的坍塌,而且要防止地下水和地表水流入基坑中,为此需修筑保护基坑的临时结构即围堰。围堰按材料可分为土围堰,草(麻)袋围堰等数种,围堰类型的选择主要根据基础尺寸,埋深以及桥址的地质,水文条件等。 当河水水深在2m以内,流速缓 When building bridges and abutments in water, it is necessary not only to prevent the collapse of pit walls but also to prevent the inflow of groundwater and surface water into the foundation pit. Therefore, temporary structures for protecting foundation pit, ie cofferdam, are to be built. Cofferdam according to the material can be divided into soil cofferdam, grass (linen) bag cofferdam and so on, cofferdam type selection mainly based on the basic dimensions, depth and the site of the bridge geological, hydrological conditions. When the river depth of less than 2m, slow speed