Pilot in situ auger mixing treatment of a contaminated site. Part 1: treatability study

The work presented in this two-part publication covers certain findings of a research contract and related studies to develop an in situ stabilization/solidification treatment methodology using auger mixing for a contaminated site at West Drayton. This paper, Part 1, contains the introduction, site details and results of the laboratory treatability study and Part 2 details the prototype auger development, site trial and assessment of the in situ treatment. The objective of the treatability study was to develop soil-grout mixes appropriate for the site soils and in situ application process with emphasis on low cement and grout content. The site investigation work revealed two distinct soil types-made ground and sand and gravel-and a wide range of contaminants. Cement-based soil-grout mixes were developed based on available strength, durability, permeability, compressibility and leachate pH design criteria. Constituents of the soil-grout mixes, which included cement, pulverized fuel ash and lime, and their ratios were varied. Contradicting requirements for satisfying some of the criteria meant that the developed mixes had to be a compromise. The applicability for stabilized contaminated ground of the permeability and freeze-thaw durability criteria considered was questioned. The work resulted in the selection of seven mixes for the site trial, detailed in Tables 3 and 8.