Determination of organic soils permeability using the piezocone dissipation test

The hydraulic conductivity, which is among other parameters, needed to predict time-dependant settlement, can be estimated using a piezocone dissipation test. This test is commonly used together with cone penetration tests (CPTs), soil borings and laboratory tests in foundation site investigations. The piezocone dissipation test is based on the fact that the rate of decay of the large excess pore water pressures generated during penetration of the piezocone through saturated clays and silts depends on the hydraulic conductivity of the material. However, interpretation of the dissipation curve is often problematic as existing methods of analysis assume a continuous decrease of pore pressure with time, whereas actual dissipation curves often exhibit non-standard behavior, the interpretation of which is more complex.
This paper presents a new method of interpretation that can be used to estimate the hydraulic conductivity regardless of the shape of the dissipation curve. Examples of results using the new analysis method are compared with results obtained using laboratory oedometer testing.