Thirty-seven-year investigation of quicklime-treated soil produced by deep mixing method

Abstract

The deep mixing method was developed in Japan and Scandinavian countries in the 1970s. Subsequently, considerable research studies have been carried out on the strength characteristics of treated soil, the interaction of treated soil and surrounding soils, the development of new binders, the development of new execution machines and techniques, the establishment of design procedures and so on. However, long-term changes in the properties of treated soil have not yet been clarified. Two columns of in situ quicklime-treated soil in a soil tank for more than 37 years were analysed in this study. Laboratory tests were conducted on them at curing periods of 11, 27 and 37 years. This paper presents the change of wet density, water content, unconfined compressive strength and calcium content. Additionally, needle-penetration resistance, pH and electrical conductivity were measured in order to reveal the deterioration properties from the surface exposed to soil for more than 37 years. The results showed that the strength of the in situ quicklime-treated soil remained, even after 37 years. However, the deformation modulus tended to decrease and the treated soil deteriorated from the surface.

Effect of curing conditions on long term mechanical property of improved surplus soils

“…It was reported in the previous studies that leaching of Ca with a decrease in pH value caused the decline in strength of the improved soils [1][2][9][10]. As introduced more in detail by the authors [8], it was also known that there were several possible states of Ca in the improved soils.…”

“…As schematically shown in Fig. 1, effect of water infiltration caused by rainfall and ground water would not be negligible on the mechanical property of the improved soil, whose binder content is smaller and permeability is higher than the improved soils by deep mixing method [1][2][3][4]. In general, it is well known that the strength of the improved soils increase with the curing period under controlled laboratory conditions, due to the chemical reactions between soil and binders.…”

Numerical Modeling of Sandy Subgrade Reinforcement by Deep Soil Mixing from Ceramic Industries Wastewater Additive

“…Takahashi, at al. mentioned the use of Sodium meta-silicate alkaline wastage as cemented in deep soil mixing for stabilization and increasing soil strength (Takahashi, Morikawa, Fujii, and Kitazume, 2018). Saberian et al studied dimensions and distance of elements or load-carrying columns in road pavement by modeling in PLAXIS 3 (Saberian, Moradi, Vali, and Li, 2018).…”

A Method of Settlement Calculation of Ground Improved by Floating Deep Mixed Columns Based on Laboratory Model Tests and Finite Element Analysis

“…Deep mixing (DM), a method that forms strong columns by mixing soil and cement to improve soil bearing capacity, is a widely used method to deal with soft soil [1][2][3]. In practice, due to the deep soft soil layer, or the small upper load intensity, the mixing cement column only penetrates the thick soft soil partially and a certain thickness of soft soil under the stabilized layer usually remains [4][5][6].…”