ABSTRACT

Chapter 1 introduced the concept of Category 1 cutoff walls, which are built in the ground by rst excavating the native material and then replacing it with an engineered “backll,” typically cement based. During the excavation phase, the trench or panel must usually be stabilized against collapse by employing a bentonite or polymer slurry. Only when the cutoff is being built in rock by the secant pile method is it not necessary to stabilize the excavation with this supporting slurry, although other methods, such as full-length, temporary casing, are required in extreme conditions.