Measuring Hydraulic Conductivity Using Geotechnical Centrifuge

Abstract

This study investigated the validity of hydraulic conductivity value using Mini Column Infiltration Test. Granitic residual soils from Broga Selangor, Malaysia were tested to obtain the hydraulic conductivity value in relatively shorter time. Soil samples were physically characterized before being tested using Centrifuge Mini Column Infiltration Technique. A normal 1-g Falling Head Permeability Test (K_f) was also being performed as a comparison with hydraulic conductivity value from Centrifuge Test (K_cen). For centrifuge test (K_cen), there were three factors involved; rotation speed, soil thickness and type of solution (single or mixture solution). Hydraulic conductivity value from Centrifuge Test (K_cen) also was highly depending on the Scale Factor Value (SFV). The results from Centrifuge Test showed that the higher rotation speed, the lower SFV would be. Hydraulic conductivity was decreasing with an increasing of rotation speed. The increment of soil thickness also contributed to the decrement of SFV and hydraulic conductivity value. Thus, the hydraulic conductivity value would be more accurate when higher rotation speed and higher soil thickness were applied. Hydraulic conductivity, K_cen for a single solution also showed higher values compared to mixture solutions. However, some of hydraulic conductivity value (K_cen) showed overestimated values due to the presence of cracks in the soil (mudcakes). Most of the scale factors gave low values (x<1.00) which meant x values were close to unity. The value of hydraulic conductivity for 1-g Permeability Test (K_f) was 2.08×10-6 m/s. While for 10mm soil thickness and 2500 RPM (1440 -g) velocity of a single solution, the value of hydraulic conductivity (K_cen) was 6.82×10^-4 m/s. Since the scale factor obtained was less than 1 (x = 0.74), the value of K_cen could be used as a valid number to replace the value of K_f from 1-g Permeability Test. This study concluded that by using scale factor, the relationship between HCV from Centrifuge Tests and Falling Head Permeability Tests could be known; thus, Centrifuge modeling could be developed as a valid method in determining the hydraulic conductivity of the soils.