Effect of confining pressure on soil-water characteristic curves of dual porosity soil

Abstract

Soil with two subcurves of Soil – Water Characteristic Curve (SWCC) (dual-porosity soils) might be found within various residual soils. Soils located in different depths have different confining pressure. Residual soils are found in unsaturated zone due to deep groundwater table. There is linear correlation between the hydraulic properties of the soil in the unsaturated area and that of its unsaturated properties.

This project aims to examine the influences of the confining pressure towards the SWCC of dual porosity soil.

The scope of this project involves measurements of drying and wetting soil-water characteristic curve (SWCC) using Tempe cell, pressure plate and advanced Triaxial apparatus. In this study the mathematical equations were developed to explain the effect of confining pressure on SWCC.

The experimental results indicated that dual porosity soil exhibits bimodal characteristics for the drying curve of SWCC and it exhibits unimodal characteristics for the wetting curve of SWCC. As the confining pressure increases, the air entry values, the inflection points and the standard deviation of drying SWCC increases too. In addition, the hysteresis of SWCC is becoming smaller with the increasing confining pressure.