Physical and mechanical characterization of deep soil mixing (DSM) materials: Laboratory vs construction site

Abstract

Soil mix material is a soil–cement material mixed in place. The process results in the formation of “concrete” in which the soil is being used as aggregate. The objective of this paper is to compare laboratory-proportioning tests with results obtained on three different construction sites (CS_1, CS_2, CS_3) using deep soil mixing method, establishing relationships between physico-mechanical properties of laboratory and construction site materials. In CS_1, Deep Soil Mixing was used to make a temporary retaining wall. Two soil-mixing columns of 80 cm diameter and 3 m depth were realized. After curing, 230 cylindrical specimens of Φ 10 × 20 cm and 130 samples of Φ 5 × 10 cm were drilled. In CS_2 and CS_3, Trench mix method was used for cut-off walls construction. In these sites, 48 specimens and 22 specimens of Φ 11 × 22 cm of fresh mixed-soil were collected, respectively. Two types of soils, from 1 and 3 m depth, were collected from CS_1 to prepare soil–cement laboratory specimens. Soil-cement mixtures contain different cement contents (100, 150, 200, 250 and 300 kg/m3), and 50 % water content. Compressive strength, dynamic modulus, porosity and hydraulic permeability are investigated. The influence of cement dosage and soil type is discussed. There is a close fit between the laboratory results and the site results for soils with low clay content. The difficulty of uniformly mixing the clay results in a lower performance of the mixed in place material compared to the laboratory material.