Slurry cut-off walls are non-structural walls constructed underground to act as barriers to the lateral flow of water and other fluids. Principal applications are site dewatering, pollution control, and seepage barriers in the foundations of water retaining structures. In this paper, the two basic types of trench — soil bentonite (SB), and cement-bentonite (CB), and the principal kinds of slurry trenching equipment are discussed. There are examples of several recent projects with emphasis on the reasons behind the selection of the particular method.
Slurry cut-off walls normally have permeability in the range of 10^-6 to 10^-7 cm/sec. Recent advances in methods of analysis of slurry cut-off walls for the key factors of permeability and durability have provided much-needed assistance in the design process. The primary purposes of quality control are to check the continuity and depth of the wall, and to ensure a slurry and backfill which fall within workable limits while satisfying design criteria.