American Society of Civil Engineers


Microporosity Structure of Coarse Granular Soils


by L. M. Zhang, (corresponding author), M.ASCE, (Associate Professor, Dept. of Civil and Environmental Engineering, The Hong Kong Univ. of Science and Technology, Clear Water Bay, Hong Kong E-mail: cezhangl@ust.hk) and X. Li, (Associate Professor, School of Civil Engineering, Beijing Jiaotong Univ., Beijing, China. E-mail: gipsy456@gmail.com)

Journal of Geotechnical and Geoenvironmental Engineering, Vol. 136, No. 10, October 2010, pp. 1425-1436, (doi:  http://dx.doi.org/10.1061/(ASCE)GT.1943-5606.0000348)

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Document type: Journal Paper
Abstract: To date the microporosity structures of coarse soils with various coarse/fines contents are still not fully understood. In this study, the pore-size distributions (PSDs) of five types of soil varying from gravel to clay were characterized using mercury intrusion porosimetry. The soil with a coarse content below 70% (i.e., fines content above 30%) is found to have a fines-controlled microstructure, which is sensitive to water content changes. Such soil forms a dual-porosity structure due to compaction, in which both intraaggregate pores and interaggregate pores are dominant. After saturation, the dual-porosity structure evolves into a unimodal porosity structure dominated by the intraaggregate pores. During drying, such soil exhibits a significant reduction of total volume. The soil with a coarse content above 70% instead has a coarse-controlled microstructure, which is stable upon water content changes. Such soil maintains dual-porosity structures no matter if the soil is compacted, saturated, or dried. As an example of application, the measured PSDs are used to predict the soil water characteristic curves (SWCCs) for the test soils and the predictions are consistent with the SWCCs measured in the laboratory.


ASCE Subject Headings:
Coarse-grained soils
Hydraulic conductivity
Microstructures
Porosity
Soil compaction
Unsaturated soils

Author Keywords:
Coarse-grained soils
Hydraulic conductivity
Microstructure
Microporosity
Soil compaction
Unsaturated soils