Bimodal SWCC and Bimodal PSD of Soils with Dual-Porosity Structure

Abstract

The soil–water characteristic curve (SWCC) and pore-size distribution (PSD) are fundamental characteristics of soils that determine many physical and mechanical properties. Recent studies demonstrate that both SWCC and PSD sometimes exhibit a bimodal feature. In this paper, soils with bimodal SWCCs are mainly divided into three categories: gap-graded soils, compacted clayey soils, and natural dual-porosity structural soils, from the perspective of microporosity structure. Based on the Fredlund and Xing unimodal SWCC equation, a bimodal SWCC equation is presented. The bimodal PSD equation d v / d log r for mercury intrusion porosimetry (MIP) is derived theoretically, according to the relationship between the mercury intrusion process in MIP and the water desorption process along the drying SWCC. These two associated equations have the same set of parameters, so the corresponding relationship between the bimodal SWCC and bimodal PSD can be directly shown. Three main presenting forms of PSD in MIP tests are summarized. Regression analysis results show that the proposed PSD equation can well fit bimodal PSD experimental data of various soils in the literature, and the SWCCs are predicted at the same time.

Determining the Bimodal Soil–Water Characteristic Curve of Fine-Grained Subgrade Soil Derived from the Compaction Condition by Incorporating Pore Size Distribution

“…Thus, the relationship between PSD and SWCC is further investigated. Previous studies indicated that the MIP test is believed to be accurate in the low and medium suction range (i.e., medium and large pores) and is used in related studies to determine For water in the unsaturated soil, a similar relationship exists for matric suction s and pore diameter d, as shown by Equation (3).…”

“…The soil-water characteristic curve (SWCC) is an essential relationship between soil suction and water content in unsaturated soils [1,2]. Besides the water retention capacity, SWCC could be used to investigate and predict several geotechnical properties of unsaturated soils, including the unsaturated shear strength [3][4][5][6][7], stress-strain relationship [8,9] and unsaturated permeability [10][11][12]. The SWCC of soils with different soil types and particle characteristics differs significantly.…”

Effect of Initial Conditions on the Pore Structure and Bimodal Soil–Water Characteristic Curve of Compacted Granite Residual Soil

“…With the development of microscopic structure detection techniques, it was found that the pore structure of unsaturated soils could be influenced by the initial conditions, and thus affected the SWCC [18]. To obtain the pore structure information, two methods are commonly used: the scanning electronic microscope (SEM) and mercury intrusion porosimetry (MIP) [19,20]. Through MIP tests, the pore structure characteristic can be quantitatively obtained.…”