Abstract
Calcareous sand is developed by the fracture of marine biological skeleton under the impact of seawater. Calcareous sand is not transported in the process of deposition. Therefore, calcareous sand retains the characteristics of marine biological skeleton, low strength, and porous. In order to study the effect of nanoclay and cement on the modification of calcareous sand, a series of tests were carried out on the modified cement calcareous sand (CCS) with different content of nanoclay. In this study, the triaxial mechanical properties and failure modes of nanoclay and cement composite modified calcareous sand (NCCS) were studied through the triaxial UU test. Then, SEM tests were carried out on CCS and NCCS samples, and the micromechanism of nanoclay and cement composite modified Nanhai calcareous sand was analyzed. The results showed that (1) the shear properties of CCS could be improved by adding nanoclay. The optimum admixture ratio of nanoclay was 8%, and its peak stress was 23%-39% higher than that of CCS. (2) The peak stress and strain of NCCS showed a linear correlation. (3) Compared with CCS, the internal friction angle and cohesion of NCCS were increased by 5.2% and 52%, respectively. (4) Nanoclay could improve the compactness and structure of cement calcareous sand, and the macroscopic performance is the improvement of peak stress and cohesion.
Highlights
calcareous sand (CCS), the internal friction angle and cohesion of nanoclay and cement composite modified calcareous sand (NCCS) were increased by 5.2% and 52%, respectively
Calcareous sand is the accumulation of pieces of carbonate materials, which are usually developed from shell fragments and skeletal debris of marine organism [1, 2]
Wang et al [18] studied the effect of cement content on the shear performance of calcareous sand through the triaxial test, and the result showed that the addition of cement could improve the shear strength of calcareous sand
Summary
Calcareous sand is the accumulation of pieces of carbonate materials, which are usually developed from shell fragments and skeletal debris of marine organism [1, 2]. ≤3 studied the influence of different cementitious materials on calcareous soil shear performance via triaxial test, and the result showed that compared with calcite powder and gypsum powder, the cementation degree of silicate cement to calciferous sand was better. Wang et al [18] studied the effect of cement content on the shear performance of calcareous sand through the triaxial test, and the result showed that the addition of cement could improve the shear strength of calcareous sand. Li et al [28] explored the effect of nanoclay on the shear performance of soft clay through the direct shear test, and the result showed that the addition of nanomontmorillonite can increase the shear strength and internal friction angle of the clay. We hoped that the outcomes of this study will provide convincing evidence on the role of nanoclay in a mixture, but can serve as a useful reference for engineering applications of NCCS in offshore engineering and for relevant theoretical developments
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