Application of deep mixing method to soft cohesive soil residue (slime)

Ground improvement (deep mixing treatment work) was conducted during Tokai Kanjo Expressway construction work. The target ground has been subjected to repeated open pit mining and burial in the past, and the buried soil is a residue (slime) mainly consisting of a dehydrated cake of soft cohesive soil generated during stone crushing. Based on the results of the laboratory mixing test, we conducted test construction to confirm the compatibility with the actual ground and the effect on construction when the water-hardening material ratio was set to 2.0. The usual construction method (single stirring) of only slurry injection with W/C = 2.0, mixing with preliminary water drilling, and stirring and mixing again with slurry injection of W/C = 1.0, resulting in a total of W/C = 2.0. As a result of implementing the construction method (double stirring), we were able to satisfy the required quality in double stirring. We will also report on construction management and quality control during this construction.1,2,3,4)