Soil settlement part 1
Soil deformation
When a soil mass is subjected to loading, such as loads due to embankment, soil settlement occurs. Regarding the time of soil deformation, settlements can be divided into 2 categories including elastic settlement and soil consolidation. Short term settlement occurs immediately after loading in all kinds of soils. Consolidation is a phenomenon that happens only for saturated and nearly saturated soils.
On the other hand, soil settlement can also be categorized into elastic and plastic settlements based on a structural point of view. Elastic deformation is reversible by unloading, while plastic deformation causes a permanent settlement. A brief summary of different technical terms has been categorized below:
- Short term settlement
- elastic settlement
- non-elastic settlement due to air going out of soil
- non-linear settlement due to water immediately going out of soil
- long term settlement
2-1 primarily consolidation
2-2 secondary consolidation
For most of geotechnical projects we need to calculate the amount of elastic settlements as well as primary and secondary consolidations.
Soil consolidation
One-dimensional consolidation is divided into three steps including initial compression, primary consolidation, and secondary consolidation. Since the compressibility of pore water is trivial, the amount of initial one-dimensional compression of saturated clay is negligible. Primary consolidation is usually identified by a S-shaped curve to compare settlement vs. log time. And finally soil secondary consolidation, also known as soil creep, happens over a long period of time.
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