ABSTRACT
Eighteen plane strain model tests were carried out on a rigid footing resting on an extended uniform collapsible soil formed of well graded sand mixed with 20% Kaolinite by weight. The tests were performed in a special rig allowing for increments of vertical loads to be applied to the footing. A uniform flow of water across the whole width of the model could also be achieved in both downward and upward directions, soaking pressures (which is defined as the pressure at inundation) of 50,100,200 and 400 kN/m2 were applied to the footing and the corresponding collapse settlement of the footing as well as surface movements were measured for both cases of downward and upward flow. Two cases of soil treatment were also studied under the above conditions, namely soil replacement with and without geogrid reinforcement. It was found that collapse settlement increases with the increase in soaking pressure. The collapse settlement increases as the depth of wetting increases in case of downward flow but the strain is less at lower levels Generally, the maximum collapse strain in case of downward flow was greater than that of upward flow. Soil treatment using sand replacement with and without reinforcement resulted in a significant reduction in collapse settlement.
