Pore water pressure profile development through soil water characteristics curve determination utilizing the continuous pressurization method

In order to improve the efficiency of the Soil Water Characteristics Curve (SWCC) determination and shorten the testing time, a new SWCC obtaining method utilizing the Continuous Pressure Method (CPM) was developed. The newly developed system allows continuous measuring of the suction by pressurizing the sample and continuously measuring the developing pore water pressure using a micro-tensiometer installed at the center of the sample. The suction (s) is defined as the difference between the applied air pressure and the measured pore water pressure at the center of the specimen (s = u_a - u_w , where ua = air pressure, u_w = pore-water pressure). Both the drying and wetting (SWCC) can be obtained in 2 to 3 days. It is found that the SWCC under both the drying and the wetting phases obtained using newly developed apparatus are in well agreement with those obtained using the conventional multi-step flow method. In addition, the optimum pore-water pressure measuring point was clarified by measuring the pore water pressure at four different levels and comparing the results. Where it was found that the SWCC obtained considering the pore-water pressure being measured at different levels agree well with SWCC obtained considering the pore-water pressure being measured at the center of the specimen. Finally, it was concluded that the pore-water pressure measured at the center of the specimen can be considered as a representative point for obtaining reliable SWCC.