Trench Cutting Remixing Deep (TRD) Method for Vertically Mixed-In-Place Cutoff Wall Construction at Herbert Hoover Dike

The Trench Cutting Remixing Deep (TRD) method of cutoff wall construction is an innovative method of deep soil mixing developed in Japan. It employs a tool resembling a "vertical chainsaw" that is installed full-depth and then crawls horizontally while simultaneously cutting and mixing in-situ soil with injected grout, without creating an open trench. The TRD method is ideally suited for projects requiring a very high quality wall or for conditions where typical slurry wall construction methods would be difficult. It is presently being used to build a seepage cutoff wall through the existing, earthen dike around Lake Okeechobee (Herbert Hoover Dike) in Florida, USA. A previous attempt at building the cutoff wall using traditional methods failed due to challenging geologic conditions. In particular, there are highly variable fill materials within the dike and natural soils below consisting of interbedded coarse grained sand, shell and soft to very hard karstic limestone. This paper provides an overview of the TRD method and covers its implementation at Lake Okeechobee, including partial results of extensive quality control testing. 10 pp., 10 figures, 10 references.