Using the Effective Void Ratio and Specific Surface Area in the Kozeny–Carman Equation to Predict the Hydraulic Conductivity of Loess

Many modified Kozeny–Carman (KC) equations have been used to predict the saturated permeability coefficient (Ks) of porous media in various fields. It is widely accepted that the KC equation applies to sand but does not apply to clay. Little information is available to clarify this point. The effectiveness of the KC equation will be evaluated via laboratory penetration tests and previously published data, which include void ratio, specific surface area (SSA), liquid limit (LL), and permeability coefficient values. This paper demonstrates how to estimate the SSA of cohesive soil from its LL. Several estimation algorithms for determining the effective void ratio (ee) of cohesive soil are reviewed. The obtained results show that, compared to the KC equation based on porosity and geometric mean particle size (Dg), the KC equation based on the SSA and the ee estimation algorithm can best predict the Ks of remolded loess. Finally, issues associated with the predictive power of the KC equation are discussed. Differences between measured and the predicted Ks values may be caused by the uniformity of the reconstructed specimen or insufficient control of the test process and errors in the SSA and ee.

Method of Designing Bentonite/Sand Mixture to Achieve the Target Permeability

Bentonite/sand mixture is expected to be an effective component of barriers for radioactive waste disposal facility. Impermeable mixture can be obtained through enrichment of the bentonite content,but it is difficult to estimate a permeability of bentonite/sand mixture before permeability test. At designing of bentonite/sand mixture, we have to decide which sand to be used, and what bentonite content is. But.this means that designing will be a time-consuming task. In this report, we made many kinds of bentonite/sand mixtures using some kinds of sand with different bentonite content, and permeability tests were conducted for these mixtures. After examination of the permeability tests results, the effective void ratio of bentonite/sand mixture which was obtained by compaction test, is an efficient parameter for estimation of the permeability. Last of all, we propose the method of designing bentonite/sand mixture using the effective void ratio.