Collapsible soil, in general, can be termed as soil that suffer or may susceptible to sudden and large volume changes under change in moisture content. The volume change is always reduction and change in moisture content means get wet of this soil.
The determination of collapse potential of collapsible soil, geotechnical properties and performance under rainfall etc. were discussed in our previous posts.
As discussed in last post collapsible soil induced foundation settlement is considered secondary foundation settlement as they can suffer settlement without increasing load or overburden pressure.
The common types that are found in United States are of two:
- Fill deposit
- Natural soil
1. Fill deposit:
Here we are concerned with uncontrolled fill, now what is uncontrolled fill?
Uncontrolled fills are that
- Not documented under compaction test while fill materials are placed including
- dumped fills
- under water dumping of fill materials
- fills placed hydraulic
- Fills compacted but have not documented about testing or effort types or amount of required compaction. The effort type is important as same compaction mechanism have different efficiency in different soils.
Uncontrolled fill is observed now in rural areas having less care in inspection or structures which were built in many years ago when rigorous compaction requirements were not developed.
In loose deposit reduction in negative pore water pressure do the harm to foundation soil. Dear reader in next part we will learn about mechanism of collapse of filled deposit and natural deposit as will; please stay with us.