SPATIAL VARIABILITY IN PROPERTIES OF CEMENT-STABILISED SOILS

Abstract

In-situ ground improvement techniques involving cement stabilisation such as Deep Cement Mixing, Jet Grouting, Cutter Soil Mixing and Mass Soil Stabilisation have gained huge popularity worldwide in the last few decades. These techniques have a faster pace of construction, are applicable to wide range of problematic soils including very soft soils/contaminated soils, have high efficiency in terms of bearing and limiting settlements/movements, can control seepage, and are cheaper and greener technology than piling. Due to the absence of proper design guidelines on mixing parameters to achieve the required degree of improvement, the impact of appropriate proportion of water content, cement content, and curing time on the properties of cement-stabilised soils are essential. In this study, the field data for UCS, Young’s modulus, permeability and unit weight are collected from over 50 sites worldwide from the existing literature. The data is majorly analysed for two different mixing techniques, i.e., Deep Soil Mixing (DSM) and Jet Grouted Piling (JGP), to assess the effect of the mixing method on the mean and the coefficient of variation (COV) of different properties of the improved ground. The influence of different types of in-situ soils, such as clays, sands, peats and mixed soils, is also assessed on the spatial variability of different field properties. The mean and COV values for Eu and ρ are also computed and compared for different mixing methods and in-situ soils. In addition, the Pearson correlation coefficients between UCS- Eu and UCS-ρ were also computed for different sites. A comparative assessment is also done to understand the influence of various mixing methods and the type of in-situ soil on the spatial variability of varying field properties. To show the effect of the spatial parameters such as COV and SOF, a braced excavation problem with spatially variable JG/DSM slab is analysed in finite element software OPTUM G2. Two types of finite element analysis – Deterministic and Stochastic analysis were performed, and the effect of properties of jet grouted slab and spatial variability in the cement treated jet grouted slab on the basal heave stability for braced excavations is also investigated.