Effect of Initial Compaction State on Near-Saturated Hydraulic Conductivity

• Published in: Journal of irrigation and drainage engineering 2019-12, Vol.145 (12)
• Main Authors: Ghosh, Biplab, Pekkat, Sreeja
• Format: Article
• Language: English
• Subjects: Cohesive soils; Compaction; Dry density; Gravimetry; Hydraulic conductivity; Hydrology; Infiltration; Moisture content; Pressure head; Regression analysis; Saturation; Soil; Soil compaction; Soil types; Soils; Statistical analysis; Technical Papers; Water content
• ISSN: 0733-9437; 1943-4774
• DOI: 10.1061/(ASCE)IR.1943-4774.0001428

AbstractQuantification of water infiltrating into the subsurface is mandatory for hydrological modeling of irrigation and drainage projects. Infiltration is influenced primarily by the soil type and initial compaction conditions (dry density and water content). However, few studies have investigated the effect of initial compaction condition on infiltration characteristics of soils and their quantitative relationship. Recent developments such as the portable mini disc infiltrometer (MDI) permit controlled, nondestructive and nonintrusive infiltration measurements in the laboratory, thereby allowing experiments under known initial compaction condition. Based on these measurements, this study developed multiple linear regression (MLR) equations relating near-saturated, near-surface hydraulic conductivity (k), and initial compaction state (dry density, γ; and gravimetric water content, w), with and without consideration of negative pressure head (h) for a cohesive and a noncohesive soil. The developed relationship was found to be statistically significant. For a particular initial w, the infiltration and k decreased with an increase in γ. For a particular γ, the k determined from infiltration measurements decreased with an increase in initial w for both soils. The developed MLR equations were used to study the effect of input variables (w, γ, and h) on k by using the method of difference. It was found that k is more sensitive to initial γ than to w and h, which have comparable influence. The role of sorptivity on the determination of k was investigated by comparing analysis methods from the literature. For lower k values (≤15  mm/h for noncohesive soil and ≤8  mm/h for cohesive soil), the effect of sorptivity on k was found to be negligible. The influence of sorptivity was predominant when initial saturation was less than 30% for which the variation of k was within 10%.