Abstract

Geotechnical engineers face serious problems when construction sites contain collapsible soils, which are known by their strength when dry and experience sudden and excessive settlement when inundated. The amount of soil collapse depends on the extent of the wetting zone and the degree of saturation reached when the surface water is the source of inundation. On the other hand, full saturation of the collapsible soil and accordingly, the maximum collapse are expected when the source of inundation is the rise of groundwater table. In this thesis, experimental investigation was carried out on prototype set-up to simulate the case of a surface rigid strip footing resting on collapsible soils. The objective of this research has been to evaluate the collapse settlement of the footing when the collapsible soils are subjected to full inundation due to the rise of ground water table. The case of footings on homogeneous collapsible soils having various collapse potentials, heights and applied stresses were first examined. Then, the case of footing resting on partially replaced collapsible soils by compacted sand was tested to establish the optimum thickness of the soil replaced on the collapse settlement of these footings. In addition, tests were carried out on these footings where geosynthetic layers were placed at the interface between the replaced and the collapsible soil layers and within the replaced soil layer. Analytical and empirical models were developed to predict the collapse settlement of these footings for a given soil / replacement layer / geotextile layer conditions. Design procedures and charts were provided for practicing use.