There are two common modes of settlement of non-free-draining soils (fine-grained soils, fine sand, and medium sand with fines greater than 10%). One is the natural drainage of water from the soil due to a hydraulic gradient. This is called self-weight consolidation. The other is the application of a load that immediately increases the porewater pressure above its current value. This is called excess porewater pressure. When this excess porewater pressure drains from the soil, the soil internal structure is forced into a denser configuration.