TABLE OF CONTENTS Saturated cohesive and organic soil can be susceptible to a large amount of settlement from structural loads. It is usually the direct weight of the structure that causes settlement of the cohesive or organic soil (i.e., first basic category of settlement, see Sec. 7.1). However, secondary influences such as the lowering of the groundwater table can also lead to settlement of cohesive or organic soils. The settlement of saturated clay or organic soil can have three different components: immediate settlement, primary consolidation, and secondary compression.
Immediate settlement ( also known as initial settlement, s i). In most situations, surface loadings causes both vertical and horizontal strains, and this is referred to as two- or three-dimensional loading. Immediate settlement is due to undrained shear deformations, or in some cases contained plastic flow, caused by the two- or three-dimensional loading (Ladd et al., 1977; Foott and Ladd, 1981). Section 8.3 will be devoted to immediate settlement.
Primary consolidation s c. The increase in vertical pressure due to the weight of the structure constructed on top of saturated soft clays and organic soil will initially be carried by the pore water in the soil. This increase in pore water pressure is known as an excess pore water pressure ( u e). The excess pore water pressure will decrease with time, as water slowly flows out of the cohesive soil. This flow of water from cohesive soil (which has a low permeability) as the excess pore water pressures...
