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Effect of Water-Cement Ratio and Liquidity Index on the Deep Mixing Method using Cement Slurry: A Case Study of Kaolin Clay Powder SOME, Donzala David; USUI, Hirofumi; MITSUSE, Kimihiro; SINDETE, Mathiro Jose; PASTOR, Jose Luis; HINO, Takenori
Lowland Technology International Vol 24 No 4 (2024): Lowland Technology International Journal
Publisher : International Association of Lowland Technology

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.0001/ialt_lti.v24i4.1714

Abstract

The liquidity index is a crucial factor in geotechnical engineering used to assess soil behavior under varying loading conditions. It provides valuable information about a soil's deformability when subjected to loads, which is vital for structural and foundation design. In the domain of soil-cement, especially within the deep mixing method (DMM), various factors influence the strength of cement-stabilized soft soils. These factors include water content, cement content, water-cement ratio (W/C), and soil consistency. Notably, a lower W/C ratio tends to result in higher unconfined compressive strength (). In the case of the Saga lowland, where soft cohesive soil with high compressibility and low strength is prevalent, the standard practice employs a W/C ratio of 1.0 with a cement content of 110 kg/m³ for most projects. However, this research introduces an innovative approach: utilizing a W/C ratio of 1.5 with the same cement content of 110 kg/m³, through laboratory experiments. It investigates the effects of the Liquidity Index (IL), instead of soil sensitivity, and the water-cement ratio on the unconfined compressive strength of specimens prepared using commercial kaolin clay powder. These specimens are prepared with varying initial water content (), determined based on the liquid limit value (), to achieve different soil states. As a result, there is a slight reduction in strength, but it is more uniformly distributed. This approach is designed to bolster support for the existing infrastructure in the Saga lowland. The significance of this study in the field of DMM lies in advocating for an increased W/C ratio to ensure not only the quality of the mixture but, more importantly, the uniformity of strength within the columns. In this context, the optimal ratio depends on a soil candidate consistency parameter, such as its IL.
Consideration of quality control standards through splitting tensile strength evaluation of plate-like improved soil SINDETE, Mathiro Jose; Usui, Hirofumi; Hino, Takenori
Lowland Technology International Vol 24 No 4 (2024): Lowland Technology International Journal
Publisher : International Association of Lowland Technology

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.0001/ialt_lti.v24i4.1739

Abstract

The Saga lowlands in Kyushu, Japan, face significant settlement issues in embankments due to the high compressibility, sensitivity, and low permeability of Hasuike and Ariake clays. To address these challenges, a combination of columnar and plate-like ground improvement techniques is used. However, natural disasters, such as earthquakes, have revealed the inadequacies of current quality control methods, leading to structural failures. This study aims to enhance quality control for plate-like improved soil constructed using slurry methods by organizing field data based on design standard tensile strength (σtk), field standard tensile strength (σtf), and lab standard tensile strength (σtl). It also investigates the relationship between unconfined compressive strength (qu) and splitting tensile strength (σt) through laboratory experiments. Hasuike clay was treated with varying binder dosages and a water-cement (W/C) ratio of 1, to evaluate the strength ratio (α) between qu and σt after 28 days of curing. Key findings show that setting σtl at 2.0 times σtf effectively minimizes the risk of falling below σtk, thereby enhancing soil performance. Laboratory results indicate that the strength ratio α for Hasuike clay varies with cement content, showing mean values between 0.12 and 0.15, with optimal combinations yielding values from 0.21 to 0.28, which is higher than the empirical standard of 0.1. Conversely, less favorable combinations with minimum values resulted in α values between 0.05 and 0.07, which should be carefully considered when designing plate-like improved soil. These results underscore a statistical and systematic approach to quality control in ground improvement projects to ensure the durability and stability of soil structures in challenging environments like the Saga lowlands.