Strength and Deformation Characteristics of Calcareous Sands Improved by PFA
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pISSN 1226-7988, eISSN 1976-3808 www.springer.com/12205
DOI 10.1007/s12205-020-0458-7
Geotechnical Engineering
Strength and Deformation Characteristics of Calcareous Sands Improved by PFA Qing-Sheng Chena, Wan Penga, Gao-LiangTaoa, and Sanjay Nimbalkarb a
Hubei Provincial Ecological Road Engineering Technology Research Center, Hubei University of Technology, Wuhan 430068, China School of Civil and Environmental Engineering, University of Technology Sydney (UTS), Ultimo NSW 2007, Australia
b
ARTICLE HISTORY
ABSTRACT
Received 16 March 2020 Revised 19 July 2020 Accepted 13 August 2020 Published Online 9 November 2020
Calcareous sand is widely distributed in the islands of the South China Sea, which could be promisingly used as the construction materials. However, particle breakage commonly occurs in calcareous sands, which may significantly influence their mechanical characteristics. To address these issues, an eco-friendly agent, i.e., polyurethane foam adhesive (PFA) is proposed to improve the engineering properties of calcareous sands, compared to the commonly used alkaline stabilizing agents (e.g., lime, cement). The objective of this work is to examine the effectiveness of using PFA in improving the strength-deformation properties of calcareous sand. A series of laboratory tests including direct shear tests, unconfined compression tests, and oedometer tests were performed on the calcareous sands improved by PFA. In addition, A scanning electron microscope (SEM) was conducted to reveal microstructural analysis of using PFA for calcareous sand. The experimental results provided insights into the shear strength, deformation modulus, as well as the micro-structural characteristics of improved calcareous sands with various PFA contents and particle size distributions.
KEYWORDS Calcareous sand Polyurethane foam adhesive Particle size distribution Strength Deformation
1. Introduction Calcareous sands usually refer to granular materials containing more than 90% calcium carbonate. It is widely distributed in the continental shelf and coastline between 30° north and 30° south latitude, including the Southern China Sea islands and reefs, the continental shelf in Western Australia, the Red Sea and the Bath Strait. Calcareous sands particles are the products of fragmentation, transportation and stacking of the wreckage and shell of herbaceous organisms. Since, most of these particles have not been transported and deposited for a long time during the formation process, the original organism and the biological skeleton with fine pores are preserved, and the fine pores are retained directly in the particle skeleton. Therefore, calcareous sands particles are generally highly porous, irregular shape, easy to break and bond and other physical properties, which are obviously different from the engineering mechanical properties of general terrestrial and marine sediments (such as quartz sand, river sand) (Wang et al., 2011, 2017; Meng et al., 2014; Yu, 2017; Shen et al., 2018). Due to these physical properties, particles b
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