Field Sampling and In Situ Testing of Soil-Cement Mixtures Used in Soil Mixing and Slurry Trenching

Soil mixing and soil-bentonite-cement slurry trenching methods produce a soil-cement product that can be classified as an intermediate geo-material (IGM). Field sampling and testing for quality control are critical in evaluating the engineering properties of these materials. An effective field sampling and testing program is one that provides an accurate representation of the resulting IGM. While there are several standards for field sampling and testing geo-structural materials, few were developed specifically for soil-cement mixtures created by soil mixing or slurry trenching methods. Available field sampling and testing methods and standards originally developed for other materials need to be carefully applied to soil mixing and slurry trenching projects to ensure that the results are both meaningful and representative of the tested materials. Specifications for soil mixing and slurry trenching projects sometimes contain field testing standards or sampling/testing requirements that are not well suited for the resulting geomaterials. This paper on field sampling and testing complements a previous paper the authors published in the 2023 DFI Sixth International Conference on Grouting & Deep Mixing proceedings, which focused on laboratory testing methods. The objective of this paper is to discuss field sampling and testing methods, such as coring, in situ permeability testing, test pits, sonic drilling, and thin-walled tube sampling, and the applicability of those methods for soil-cement mixtures created in the stated applications. The paper provides recommendations for modifications to testing methods, where appropriate, for use in soil mixing and slurry trenching applications.