Pilot in situ auger mixing treatment of a contaminated site. Part 4. Performance at five years

Abstract

Parts 1, 2 and 3 of this series of publications gave details of the development and application of a pilot in situ auger mixing treatment on a contaminated site in West Drayton, Middlesex. The treatment method employed was in situ stabilisation/solidification using cement-based grouts and applied using a soil-mixing auger. In these publications, details were given of the initial laboratory treatability study, the site trial and subsequent laboratory assessment of the treated contaminated made ground using samples cored at 55 days and tested at 0·2, 1·2 and 2·4 years after treatment. Recently, further coring of the treated ground took place at 4·5 years of in situ curing and the samples were tested at around 5 years after treatment. Hence this paper presents the longer-term behaviour of the in situ cured stabilised/solidified contaminated ground in terms of physical and chemical properties such as strength, leachability, leachate pH, permeability, freeze–thaw and wet–dry durability and microstructural analyses. The performance is presented of both soil types present, made ground and sand and gravel, from both single and overlap column mixes. The paper provides an insight into the effectiveness of the treatment at 5 years, a correlation between the performance of the different soils and mix conditions, and an assessment of the applicability of the available test methods and test criteria imposed.