Evaluating the Influence of Specimen Preparation on Saturated Hydraulic Conductivity Using Nuclear Magnetic Resonance Technology

Abstract

Core Ideas Specimen preparation methods have a significant influence on hydraulic conductivity. The difference caused by different methods can be large as one order of magnitude. Soil pore structure should be considered in predicting hydraulic conductivity. A pore‐information‐based model is presented to predict hydraulic conductivity. The new model is more accurate than traditional particle information based models. A series of laboratory tests were performed to investigate the influences of specimen preparation on pore size distribution of soil and saturated hydraulic conductivity (Ks). Nuclear magnetic resonance technology was used to measure the pore size distribution of the saturated samples of silty soil, which were prepared by three different kinds of methods: Proctor compaction, static compaction, and the consolidation method. The Ks of the samples was measured by the falling head permeability test. The results show that the difference in Ks caused by different specimen preparations can be large as one order of magnitude, as the measured Ks varied from 3.09 × 10−3 to 3.36 × 10−4 cm s−1. The consolidated specimen tended to have the greatest Ks value, followed by those prepared by Proctor compaction and static compaction. The observed difference highlights the importance of pore structure in determining Ks. This study also presents a pore‐information‐based theoretical approach for predicting Ks. A comparison of measured data shows that the proposed model performs better than the traditional void‐ratio‐based models.

Experimental Study of Water Transfer and Ice Accumulation in Freezing Soils under Different Conditions

“…Besides, the other typical soil types, including calcareous sand, SSL soil, red clay in Changsha, are adopted to make a comparison of the efficiency of the vapor transfer. eir properties are available in the literature [12,18,19].…”

“…In addition, another reason is the difference in permeability of the soil sample under different initial water content. According to the study of [19], the soil sample of lower water content normally has higher permeability, which then results in a larger amount of water transferred. Furthermore, the difference in the total water in the three soil samples after tests is relatively minimal.…”

A Numerical Model of Vapour Transfer and Phase Change in Unsaturated Freezing Soils

“…A theoretical model is established to formulate the coupled thermal and hydrological process by COMSOL, where the vapour flow governs the mass transfer process. A series of laboratory test results, which are published on Geotechnique [17], are used to validate the numerical formulations/codes.…”

“…is assumption is made on the basis of the cognition that (1) neglecting the vapour flow could largely simplify the numerical computation and (2) it is truly insignificant for the vapour flow in the soil of having a continuous liquid phase. Considering that more evidence has revealed the complexity in soil freezing process, a large number of sophisticated models or parameterizations have been presented during the following several decades [13][14][15][16][17]. Some of these studies take the contribution of vapour flow and its phase change into account, while others choose to neglect yet.…”

A mathematical model of tortuosity in soil considering particle arrangement

“…The soil hydraulic conductivity is of great importance in the study of the percolation process in porous media (Bear, 1988; He, Teng, Sheng, & Sheng, 2017; Sheng, Zhang, Niu, & Cheng, 2014; Teng, Kou, Zhang, & Sheng, 2019a), consolidation and settlement of soils and foundations (Ren et al., 2016; Rodriguez, Giacomelli, & Vazquez, 2004; Zhang, Sheng, Zhao, Niu, & He, 2015), migration of pollutants from waste disposal facilities (Malusis, Shackelford, & Olsen, 2003; Yanful & Choo, 1997), and other geotechnical engineering problems. Theoretical and empirical equations relate hydraulic conductivity to soil properties like soil texture and structure, pore geometry, and chemical properties of the pore fluid (Costa, 2006; Ren et al., 2016; Teng, Shan, He, Zhang, & Sheng, 2019b; Teng, Zhang, Zhang, Zhao, & Sheng, 2019c).…”