Which type of soil is considered the least stable?

Type C soil is classified as the least stable type of soil in excavation and construction contexts. This classification is based on the properties and characteristics of the soil, which include its cohesion, moisture content, and the size of soil particles. Type C soil typically includes granular soils that do not exhibit any cohesive strength, such as sand and gravel, and can include soils that are highly disturbed or have a mixture of different particles. These properties make Type C soil more susceptible to shifts or collapses, particularly when subjected to external forces or environmental changes, such as rainfall or vibrations from machinery.

Understanding soil classifications is crucial for safety in excavation work and helps in determining the necessary precautions and support systems required to ensure stability. In contrast, Type A and Type B soils are considered more stable, with Type A being cohesive and capable of maintaining structure better, while Type B is somewhat stable but less so than Type A.