Dynamic replacement and mixing of organic soils with sand charges

Abstract

Field trials were initiated to investigate the feasibility of minimizing secondary as well as enforcing primary compression of peaty clays by dynamic replacement and mixing (DRM) with sand charges using conventional heavy tamping plant. Laboratory model tests were also conducted to amplify the field findings. The investigations have shown that DRM can transform in situ peaty clay deposits into an upper sand raft with pockets of peaty sand underlain by a fairly uniform layer of mixed sand and peat, where both sublayers have relatively insignificant secondary compression characteristics. Furthermore, for practical purposes, unique relationships may be established between degree of improvement of peaty clay after treatment (in terms of primary and secondary compression properties) and sand-charge-to-compressible-soil ratio s. Similar relations may be formulated between s and an operational factor Ω, incorporating initial soil consistency and energy-application parameters used in standard practice. By means of these characteristic relationships, overall operational requirements of a tamping scheme to achieve a desired degree of ground improvement may, in principle, be determined prior to field application.