Abstract
The air-entry value (AEV) is a fundamental parameter of the soil-water characteristic curve (SWCC). AEV is the minimum matric suction value required for entry of air into soil voids. The primary objective of this research work is to assess the impact of geotechnical index properties, swelling properties, mineral composition on AEV of compacted heaving soils, and discuss how they affect AEV. Soil properties were investigated through lab tests such as grain size distribution (GSD), specific gravity, Atterberg limits, linear shrinkage, free swell index, free swell ratio, X-ray diffraction, compaction test, and soil suction measurement. SWRC Fit program was used to perform non-linear fitting of the SWCC based on models VG, DB, FX, LN, and BL. Surface plot of data was used to characterize the impact of soil properties on AEV. It was observed that AEV is ranging from 10 kPa to 20.20 kPa, models DB and BL gives the best fitting SWCC. The percent of smectite mineral exhibits a significant impact on AEV. Swelling properties such as free swell index and free swell ratio influence the AEV with a respective determination coefficient of 85.72%, 88.68%. The plasticity index, linear shrinkage, specific gravity, and dry unit weight impact the AEV with a respective determination coefficient of 95%, 95.45%, 90.43%, 94.29%. The fine-grained content, clay fraction, void ratio, and water content influence the AEV with a respective determination coefficient of 97.95%, 84.89%, 80%, 94.31%. The finer the soil, the higher the AEV. The activity of clay and percent of illite mineral exhibit a marginal effect on the AEV.
Highlights
Introduction and BackgroundReference [1] defined the air-entry value (AEV) as the matric suction value where the air begins to enter the largest pores in the soil
The analysis reveals that the AEV relies upon the soil-water characteristic curve (SWCC) when the soil suction increases and the void ratio of the shrinkage graph displays a significant impact on SWCC
The AEV is a fundamental factor of the SWCC in unsaturated soil mechanics
Summary
Reference [1] defined the air-entry value (AEV) as the matric suction value where the air begins to enter the largest pores in the soil. Reference [7] studied the SWCC of compacted heaving soils at the various dry unit weights. Reference [4] reported that the dry unit weight influences the SWCC. [9] analyzed the impacts of initial dry unit weight on the SWCC of loose soil utilizing a pressure plate. Reference [12] investigated the impact of the initial amount of water and void ratio on SWCC. Reference [13] reported the impact of the initial void ratio on the SWCC, specimens were set up in a modified oedometer apparatus for non-saturated soils. These studies do not specify the type of correlation between the void ratio and the AEV or SWCC. An investigation of the impact of geotechnical properties, swelling properties, and soil mineralogy on AEV of compacted heaving soils is essential
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