Abstract: In recent years, hinge mattress technique is widely used because of good revetment effect. The quality of laying mattress has direct influence on the protection effect, so underground laying quality and inspection are important. As for inspection index of laying process of underground mattress, we study it by using several advanced inspection techniques. Then we apply multi-beam echo sounder to the quality inspection of underwater laying process of underground mattress, and obtain accurate data in accordance with underwater inspection indexes in Jiangsu provincial standard(Water Conservancy Project Construction Quality Inspection and Assessment Standards).The research results offer reference for quality assessment and acceptance in similar projects.

Key words: multi-beam, precast concrete slab connected with hinges, underwater laying down of precast concrete slab, inspection index, quality assessment