Long-Term Settlement Prediction of Ground Reinforcement Foundation Using a Deep Cement Mixing Method in Reclaimed Land

Abstract

The greenhouse foundation method requires a lower allowable bearing capacity compared to general buildings, but the high-spec and expensive prestressed high-strength concrete (PHC) pile reinforcement method is mainly applied. Therefore, the deep cement mixing (DCM) method, which is one of the ground reinforcement foundations that replaces the PHC piles and secures structural safety suitable for the greenhouse foundation, was considered. To verify the structural safety of the DCM method, a geotechnical survey and soil test were conducted, and a long-term settlement monitoring system was established. The specifications of the DCM foundation were designed to be 0.8 m in diameter, 3 m × 3 m in width and length, and 3 m in depth. Based on the settlement monitoring data, long-term settlement was predicted considering the greenhouse durability of 15 years. For long-term settlement prediction, the Log S–T, hyperbolic, Asaoka method, Schmertmann theory, and the finite element method (FEM) analysis were performed. In the case of the Log S–T, hyperbolic, and Asaoka method based on actual measurement data, the settlement amount was predicted to be 12.18~20.43 mm, and in the case of the Schmertmann empirical formula, it was predicted to be 19.66 m. The FEM analysis result was 8.89 mm. As the most conservative result, the DCM foundation method designed in this paper had an allowable bearing capacity of 310 kN/m2 and a long-term settlement of 20.43 mm. This is the result of satisfying both the allowable bearing capacity of 100 kN/m2 and the allowable settlement range of 25.4 mm as a foundation. Through this study, it was proven that long-term structural safety can be sufficiently secured when the DCM foundation is constructed on a soft ground through a design that considers the required service life and allowable bearing capacity of the structure. In addition, it was confirmed that the Hyperbolic, Asaoka, and FEM analysis method adopted in this paper can be applied to the long-term settlement behavior analysis of the DCM foundation method.

Experimental and Numerical Investigations of Mixing Performance of Mixing Agitators of Deep Cement Mixing Ships

“…Figure 1 shows a schematic diagram of a DCM ship. At present, most of the research on DCM technology focus on the quality of pile formation [2][3][4] and the bearing capacity of the improved soft foundation [5,6]. To the best of the authors' knowledge, there are no existing publications that have studied the mixing behaviors of agitators.…”

Strength Properties of Cement-Solidified Dredged Sludge Affected by Curing Temperature

“…Currently, the dredged sludge is often abandoned in cofferdams, occupying a large amount of land resources for a long time, which leads to social conflicts and environmental pollution [7]. In order to transform the sludge into suitable engineering materials, achieve waste utilization and sustainable economic development, chemical solidification technology using cementitious materials such as cement and lime is generally proposed and has been already applied in some construction projects, such as ports, road subbases and airports [8][9][10][11][12][13][14][15][16].…”