THE HYDRAULIC CONDUCTIVITY OF SINGAPORE MARINE CLAY AT CHANGI

The hydraulic conductivity of Singapore Marine Clay at Changi was stud ied by both in situ and laboratory methods. In situ tests, such as the Cone Penetration Test (CPT), Dilatometer Test (DMT), Self-boring Pres suremeter Test (SBPT) and BAT permeameter test were carried out. Rowe Cells and oedometers were used to determine the horizontal hydraulic c onductivity and vertical hydraulic conductivity respectively. Hydrauli c conductivity values were found to range between 10(-10) m/s and 10(- 9) m/s. Hydraulic conductivity values in the horizontal direction meas ured from laboratory Rowe Cell tests were found to be about twice the vertical hydraulic conductivity from oedometer tests. Horizontal hydra ulic conductivity values measured from Rowe Cell tests were also highe r than those measured from BAT and SEPT but about the same order as va lues obtained from CPTU and DMT. Most hydraulic conductivity values ev aluated indirectly from in situ dissipation tests were higher than dir ect measured values from BAT permeameter tests. DMT and CPTU gave the highest horizontal hydraulic conductivity values and SEPT yielded valu es in between. However CPTU, DMT and SEPT dissipation tests were found to be suitable alternative methods for estimating the hydraulic condu ctivity of clay. The variation of vertical hydraulic conductivity was characterized by the relationship between void ratio and hydraulic con ductivity change index which, based on oedometer results, is only C-kv = 0.3e(o).