A thesis submitted in partial: fulfillment of the requirement for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1980

The settlement and pore pressure- time variations of a test embankment on sand drains were analyzed by an explicit finite difference technique. The embankment was built in two stages and extended over three test sections, namely one without sand drains and the other two with drain spacings of 1.5 and 2.5 m. The soft clay had a depth of about 17 m and numerous piezometers had been installed to monitor pore pressures. Analysis, however, was carried out only for points at the center of each test section!, but at various depths. Soil parameters were obtained from laboratory oedometer tests. The analysis could take into account a multilayer soil profile, two-dimensional water flow, time-dependent loading, stress distribution varying with depth and undrained deformations. The method of analysis proved to be effective in predicting settlements and pore pressures, although in the non-sand drain area the agreement with the observed ·values was poor, the measured settlements being much larger than the observed and measured pore pressures dissipated considerably faster than the predicted ones. The closest prediction was obtained for the section with 2.5 m drain spacing. A back analysis was then carried out by fitting the predicted and observed pore pressure - time relationships at different depths. For the sand drain sections pore pressure isochrones were also established which .provided a better insight into the effect of the coefficients of consolidation for vertical and horizontal drainage during the pore pressure dissipation phase.