Abstract
Investigating the soil-water characteristics of calcareous soil has a great significance for preventing geological disasters on island-reefs as well as maintaining the foundation stability of hydraulic-filled island-reefs. In this study, calcareous silty sands with different fines contents and dry densities were studied to reveal their effects on the soil-water characteristics of calcareous soil on hydraulic-filled island-reefs. The soil-water characteristic curve (SWCC) of the calcareous silty sand was measured using a pressure plate apparatus. Taking into account the porous meso-structure, the effects of fines content and dry density on the SWCC of calcareous silty sand were analyzed, and the applicability of existing SWCC models to calcareous silty sand was verified. A SWCC model suitable for assessing soil-water characteristic of calcareous silty sand was proposed. Results of this study provide some reference for quantifying the water-holding capacity of calcareous silty sand.
Highlights
When coral polyps die, their organic remains gradually calcify, eventually forming coral reefs that can be partially exposed above sea level
Results of this study provide some reference for quantifying the waterholding capacity of calcareous silty sand
When the soil-water characteristic curve (SWCC) in the transition state was extended upwards to intersect with the horizontal line corresponding to the initial volumetric water content, the abscissa of the intersection point represents the air entry value of the sample (Figure 5)
Summary
Their organic remains gradually calcify, eventually forming coral reefs that can be partially exposed above sea level. Calcareous silty sands with different fines contents took 4–5 days to reach an equilibrium state under different air compression stresses. By monitoring the amount of water in the container under each level of air compression stress in a realtime, this study obtained the relationship between volumetric water content and matric suction, i.e., SWCC. In the boundary effect stage, the reduction of volumetric water content of calcareous silty sand with increasing matric suction further decreased with increasing fines content. The boundary effect stage corresponded to the low matric suction state, and the quantity and distribution characteristics of large pores containing free water were primary factors controlling the sample water-holding capacity within this stage.
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