What type of soil is referenced in the short term maximum allowable slope for excavations according to OSHA?

The short-term maximum allowable slope for excavations as referenced by OSHA is specifically related to Type A soil. Type A soil is characterized as the most stable type of soil for excavation purposes, typically consisting of clay, silty clay, and clay with high cohesion. Because of its cohesive properties, Type A soil allows for a greater slope when excavating, reflecting its increased stability and reduced risk of collapse.

Under OSHA regulations, the angle of repose (the steepest angle at which a sloped surface remains stable) is gentler for Type B soil, which is less stable than Type A, and allows for a more conservative approach to excavation. However, the short-term allowable slope is less steep for less cohesive materials, such as sand or non-cohesive soils, as these generally have a higher risk of failure under similar conditions. Thus, recognizing the properties of Type A soil emphasizes its suitability for deeper, short-term excavations while maintaining safety standards.