Soil liquefaction is a significant cause of damage to buildings and structures during earthquakes, with several hazards, including ground failure, lateral spreading, soil oscillation, sand boiling, loss of bearing capacity, and settlement. Various soil improvement techniques aim to enhance the mechanical properties of soil, increasing bearing capacity, reducing volumetric deformations, and providing predictable soil behavior. This study examines the effectiveness of deep soil mixing (DSM) columns in reducing liquefaction hazards beneath raft foundations using a three-dimensional finite element method in the Midas GTS NX environment. The influence of DSM column (individual and wall) arrangements, diameter, height, and area improvement ratio on the foundation in reducing liquefaction potential and specifically excesss pore water pressure has been studied. The lambda\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda$$\end{document} parameter, defined as the ratio of pore water pressure in the improved state to the unimproved state, is introduced to express the results better. The study finds that increasing the percentage of area improvement using DSM columns reduces the excess pore water ratio, and the individual column arrangement (ICA) is more effective than the wall column arrangement (WCA). The excess pore water pressure is primarily influenced by the area improvement ratio factor, as evidenced by the continued reduction of the excess pore water pressure ratio with increasing area improvement ratio in both column arrangements.

Deep soil mixing (DSM) is an established ground improvement technique employed in civil projects. Despite the superiority of field tests for understanding this technique, their high cost has directed researchers' focus on laboratory tests, resulting in limited attention given to operational factors. Consequently, in current research, a small-scale DSM setup was developed to investigate the influence of operational factors such as mixing time and execution procedure on strength and deformation characteristics of laboratory-scale DSM columns. For the installation of DSM columns, mixing times of 130, 190 and 250 seconds were used, together with normal and zigzag execution procedures, cement dosages (alpha) of 300, 400 and 500 kg/m(3), and total water-to-cement (W-total/C) ratios of 2.5, 3.0 and 3.5. Laboratory samples were also prepared using the same alpha values and (W-total/C) ratios for comparison with DSM columns. The sand bed was prepared with 5 % and 30 % moisture contents. Experimental observations showed that saturating the sand bed enhances the mixing quality by preventing slurry water infiltration into the soil surrounding the DSM columns. Results indicated that increasing mixing time and adopting zigzag execution procedure improved mixing quality, unconfined compressive strength (UCS), secant modulus (E-50), and strain at maximum stress (epsilon(Maximum Stress)), whilst reducing strength variability. Moreover, the outcomes showed that UCS and E-50 of samples have a direct and inverse relationship with alpha and (W-total/C), respectively, and that the nature of these relationships, not their magnitude, were not affected by mixing time and execution procedure. Additionally, findings indicated that the failure mode of DSM samples was influenced by operational factors, whereas (E-50/UCS) ratio was not.

This study investigated the physical and mechanical properties of Malaysian kaolin clay treated with cement using unconfined compression strength and Oedometer tests. The objective was to simulate the actual conditions of soil-cement column installation employing the deep soil mixing method with cement slurry over a 180-day period. Cement content varied between 5%, 10%, 15%, and 20%. To ensure homogeneous mixing and workability, water content was maintained between the liquid limit and twice the liquid limit. Results indicated that increasing cement content enhanced the unconfined shear strength and elasticity modulus of the stabilized soil while decreasing water content after curing. Consolidation tests revealed a diminishing slope of the void ratio curve with increasing cement content and curing time. This study further introduced precise correlations between the void ratio and compression characteristics of cement-stabilized clay, achieving high accuracy. Additionally, the research conclusively demonstrated a robust linear correlation (R2 = 0.99) between unconfined compressive strength and consolidation yield pressure.

This study examines the impact of incorporating sodium alginate (SA) biopolymer into soft clay using the deep soil mixing method (DSM). SA-stabilised samples were tested under high-moisture (A) and low-moisture (B) conditions to assess their mechanical properties, chemical attributes, freeze-thaw resistance, and microstructure. Results indicate that samples cured under condition A outperformed those in condition B, primarily due to enhanced biopolymer gel formation. In both conditions, increasing the SA content and curing time led to higher peak strength, stiffness, and pH. The higher SA ratio improved ductility in condition A but increased brittleness in condition B. At the 28-day mark, a 1.0% SA ratio and a pH range of 8.2-8.4 were crucial for specimen strength increase. Freeze-thaw cycles had minimal impact, with a modest reduction in compressive strength observed. Scanning electron microscopy showed face-to-face bonding between clay particles and the gel -like materials due to electrostatic attraction. After 14 days, ramifications occurred around the core structure, and after 28 days, high agglomeration structures appeared, attributed to clay particle flocculation. Energy-dispersive X-ray (EDX) analysis indicated an increase in the Si/Al ratio boosted sample strength, while X-ray diffraction (XRD) results showed no crystalline phase in SA-stabilised samples due to encapsulating clay minerals with gel -like materials. In summary, this study suggests that SA biopolymer offers an eco-friendly, sustainable option for enhancing soft clay with DSM.

The recent construction of an underground mass rapid transit (MRT) station in Singapore involved 21 m deep excavations within underconsolidated marine clay. The lateral earth support system comprised 1 m thick diaphragm walls socketed into the underlying Old Alluvium and 4 levels of preloaded cross-lot struts. Deep soil mixing (DSM) and jet grouting piles (JGP) were used to improve up to 15 m thickness of the marine clay formation. Field monitoring data showed that these ground improvement processes caused large outward deflections of the diaphragm wall panels at some locations prior to the excavation and may have caused yielding within the wall panels. In this paper, the impacts of these prior wall deformations on the subsequent performance of the excavation support system are investigated. The measured performance at two indicative cross sections is compared with results from simplified 2D finite element analyses. The analyses simulate the effects of ground improvement through prescribed boundary pressures and represent the yielding of the diaphragm wall panels through zones of reduced bending stiffness. We show that large outward wall deflections and curvature observed during jet grouting at one contribute to higher inward wall movements and strut loads measured during excavation, while smaller movements (and curvature) prior to excavation at a second similar cross cause negligible change in the performance of the temporary earth retaining system. The results highlight (1) the importance of controlling ground movements associated with ground modification processes such as jet grouting, (2) the uncertainties in estimating mechanical properties for the improved soil mass, and (3) the need to improve the representation of non-linear, flexural properties (M-kappa) of reinforced concrete diaphragm panels.

This paper presents a 3D finite element analysis of deep soil mixing column-supported embankments (CSEs) with a geosynthetic platform. The numerical model simulated the CSE for the expansion (approximate to 1.0 km) of the existing runway at the Salgado Filho International Airport, in the city of Porto Alegre. The numerical model using Abaqus software was calibrated by comparing numerical calculations with good quality instrumentation data. Deep Soil Mixing (DSM) columns were used to improve the soil foundation. A novel approach to modeling the geosynthetic is also presented based on the mechanical properties of this material. The load transfer mechanisms and deformation of the column-supported embankments were analyzed by means of numerical and field results. Additional aspects such as the critical height and the pattern of vertical stress distribution in the columns and embankment as well as the stress distribution in the geosynthetic reinforcement were also investigated. The numerical model reproduces the vertical stress measured by the total stress cells installed above the columns and between the columns. The numerical model shows that the soil reaction of the thick compacted layer used as a work platform reduced the arching and membrane effect in the embankment.