Report No. : GEO Report No. 193

Report Title : Laboratory Measurement of the Coefficient of Permeability Functions of Selected Hong Kong Soils (2006), 106 p.

Author : J.K.M. Gan & D.G. Fredlund

Abstract

This project is part of a study on the application of permeability functions to the stability of slopes. The study is being sponsored by the Geotechnical Engineering Office (GEO) in Hong Kong

The coefficient of permeability function is an important soil parameter in the study of problems related to potential slope instability. The coefficient of permeability directly affects the infiltration of water into a slope as well as the transmission of water through the soil comprising the slope. The coefficient of permeability decreases when the degree of saturation (or water content) of a soil decreases. In turn, the degree of saturation of a soil decreases in response to an increase in soil suction.

In this study, the coefficient of permeability functions for five selected soils from Hong Kong were measured in the laboratory. Initially, a method developed by Huang (1994) using a triaxial permeameter, was proposed for measuring the coefficient of permeability functions. Numerous attempts during the initial stages of testing showed that the method proposed by Huang (1994) would be difficult, if not impossible to use for the selected Hong Kong soils. In particular, the preparation (i.e., trimming) of suitable triaxial soil specimens for the Hong Kong soils was difficult.

A new method was therefore developed for measuring the coefficient of permeability of the Hong Kong soil specimens at various suction values. The methodology and test procedure for the new method are described in the following section.

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