Final answer:
a. During consolidation, effective stress decreases. b. Compression index can be less or greater than the swelling index. c. The larger the coefficient of consolidation, the faster is the consolidation process. d. High plastic clays have higher coefficient of volume consolidation (cv) than low plastic ones. e. The stiffer the clay, the lower is the coefficient of consolidation.
Step-by-step explanation:
a. During consolidation, effective stress decreases. Consolidation is the process by which soil settles under the action of loading. As the load increases, the void spaces in the soil get reduced, causing the soil particles to rearrange, and this results in a decrease in effective stress.
b. The statement 'compression index can be less or greater than the swelling index' is true. Compression index measures the compressibility of a soil when it is subjected to an increase in pressure, while swelling index measures the increase in volume when the soil absorbs water. These indices can have different values depending on the characteristics of the soil.
c. The larger the coefficient of consolidation, the faster is the consolidation process. Coefficient of consolidation represents the rate at which water drains out of the soil during consolidation. A higher coefficient of consolidation indicates faster drainage and thus a faster consolidation process.
d. High plastic clays have higher coefficient of volume consolidation (cv) than low plastic ones. Coefficient of volume consolidation measures the rate at which soil consolidates under loading or pressure. High plastic clays have smaller void spaces and can retain water, leading to higher cv values.
e. The statement 'the stiffer the clay, the lower is the coefficient of consolidation' is false. Stiffer clay refers to clay with higher stiffness or resistance to deformation. The coefficient of consolidation depends on the permeability and drainage characteristics of the clay, and it is not directly related to its stiffness.