A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand

Thesis (M.Eng. ) - Asian Institute of Technology, 1978

In order to evaluate the coefficient of consolidation for horizontal drainage, ch, in Porn Prachul clay, a variety of laboratory tests were conducted. These included lever-arm and Bishop oedometer tests on 2.5 inch diameter samples with a central drain as well as tests on 6 inch diameter samples in a Rowe cell. All samples were taken from a depth between 5.0 and 5.5 m. For the Rowe oedometer tests four different drain diameters were used and pore pressures were measured at the base either at two diametrically located points or at four points with different distances from the drain. The coefficient of consolidation for radial drainage was evaluated from compression-time curves in case of the lever-arm and Bishop oedometer tests and from pore pressure dissipation in case of the Rowe oedometer tests. The degree of consolidation as a function of the radial distance from the drain was compared with Barron's equal strain solution. A fair agreement, however, was only observed for intermediate degrees of consolidation. The coefficient of consolidation was also evaluated from constant head permeability tests. The values of Ch obtained by the difference tests varied from about 5 to 20.10-8 cm2/sec, with the Rowe cell tests yielding the lowest values. An analysis of settlement plate observations under a test embankment revealed that the field value of Ch could be about 5 times higher than the value obtained from the Rowe oedometer.