Abstract：The surface electrical conductivity (?s) of natural clay deposits was caused by the presence of double electric layers, which caused by its own mineral structure, around the clay particle. Different clay particle has different double layer structure, which makes the mixed conductivity (?mix) more complicated. Therefore, the aim of this study is to evaluate/estimate the influence of surface conductivity on the mixed conductivity of bentonite-kaolinite mixed soils with varying weight fraction of bentonite particles (BF=0~70%). The electrical conductivity formulas, including the effective media conductivity model used for surface conductivity assess, were reviewed, and a number of electrical conductivity measurements on bentonite-kaolinite mixtures were performed in this study using a developed oedometer cell equipped with a 4 electrodes conductivity probe. The results of this study demonstrate that the measured ?mix and surface electrical conductivity ?s of tested bentonite-kaolinite mixed soils increases considerably with an increase in BF. The comparison between the experimental results of this study and the effective media estimating formulas for mixed soils demonstrates that the modified effective media equation gives the most dependable estimate of ?mix of tested bentonite-kaolinite mixed soils. Finally, the matrix conductivity in the modified effective media equation is compared with other
related literature research data in this study.
