Abstract

This study aimed to investigate the influence of loosely bound water (LBW) on the compressibility of compacted fine-grained soils and accurately determine the soil’s compression index. Four fine-grained soils (i.e., heavy clay, heavy silt, lean clay, and lean silt) and a coarse-grained soil were examined. The volumetric flask method was used to measure the LBW contents of the five soils. X-ray diffraction (XRD) analysis was then performed to test the mineral compositions and help explain the reason why the LBW content varied between different soils. A concept of modified void ratio was proposed by assuming that LBW is a part of the solid phase in soil. Subsequently, consolidation tests and permeability tests were conducted on saturated compacted specimens. The results show that the compression indexes or permeability coefficients tend to be the same for the soils with identical initial modified void ratios. Consolidation tests were also carried out on the unsaturated compacted heavy silt of four different dry densities prepared at a water content higher than the optimum. They show that the compression of unsaturated soil occurs if pore air is discharged when the water content is less than the LBW content. This confirms the previous assumption that LBW can be regarded as a part of the soil solid phase. A modified compression index was deduced and implemented to predict the settlement of a road embankment. The result suggests that the modified compression index is capable of calculating the compression of fine-grained soils, whose water contents are higher than their LBW contents.

Highlights

  • Fine-grained soils are commonly encountered in the practice of geotechnical engineering, making it crucial to understand and predict their engineering behaviors, which are strongly dependent on water contents

  • Soil compression characteristics have consistently been the focus of attention in engineering design and construction, as the postconstruction soil settlement significantly affects the safety and stability of superstructures. erefore, it is theoretically and practically important to study the effect of loosely bound water (LBW) on soil compression characteristics

  • Since LBW is usually hard to remove from soil [25, 30], it can be regarded as a part of the solid phase in soil when the water content is greater than the LBW content

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Summary

Introduction

Fine-grained soils are commonly encountered in the practice of geotechnical engineering, making it crucial to understand and predict their engineering behaviors, which are strongly dependent on water contents. E void ratio that greatly affects the compression process of soil is a key parameter in the determination of Cc [6, 7]. TBW is tightly adsorbed on the surfaces of soil particles, and it gradually turns into LBW with weakening action of the electric double layer. Erefore, one objective of this study was to determine the LBW contents of different fine-grained soils using the volumetric flask method and to analyze the effects of LBW on the consolidation characteristics of soil specimens. The modified compression index (Cc′) was calculated by the proposed equation and compared with the conventional Cc value and the theoretical value determined based on the work of Sridharan and Jayadeva [10]. The settlement of a road embankment was predicted using Cc′ and verified with field data

Modification of Void Ratio
Experimental Program
Results and Discussion
Full Text
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