Aiming at the problems of stones and permeable frames existing in the overlap region with the former bottom protection project for soft body mattress,in order to avoid damage to the soft body mattress which had already been laid,we pave the deepwater sand quilt with the help of existing technological base and geotextiles-laying vessels.As a result of that,we achieve the goal of keeping gravel layer sealing,abandoning rocks or anything like that away from sludge and horizontal drainage flatly.