Principles and Practice of Engineering (PE) Civil: Structural Practice Exam

Secondary consolidation settlement is primarily associated with the long-term changes in the soil structure that occur after the primary consolidation has taken place. This process involves the gradual, ongoing rearrangement of soil particles as they settle under the effects of sustained loads. Over time, the soil continues to deform even after the excess pore pressures from previous loading have dissipated, reflecting its long-term behavior.

This restructuring of soil particles occurs due to several factors, including the redistribution of stress, the gradual expulsion of water, and the ability of the soil to accommodate further compression. It highlights the plastic nature of soil behavior beyond its immediate elastic deformation under load.

In contrast, immediate expulsion of water pertains to the rapid dissipation of pore water pressures during the initial stages of loading, while elastic deformation refers to temporary changes dependent on the applied stress that revert once the load is removed. An increase in pore pressure is typically associated with the initial consolidation phase rather than the long-term secondary consolidation settlement process.