What type of soil poses a greater risk during excavation?

Soft clay poses a greater risk during excavation primarily because of its inherent properties, which can lead to instability and significant hazards as work progresses. This type of soil is characterized by its high moisture content and low shear strength, making it susceptible to collapsing or heaving when disturbed. During excavation, the weight of the surrounding soil can exert pressure on the walls of the excavation site, leading to potential cave-ins.

Additionally, soft clay may hold water and become plastic or slushy when wet, further increasing the risk of unstable conditions, particularly in excavated trenches that can easily be undermined. Safe excavation practices require careful attention to the characteristics and behavior of soil types like soft clay, and appropriate measures must be taken to support walls or use shoring techniques to prevent accidents.

In contrast, stable soil has a lower risk profile due to its cohesive and structured nature, while granite is a hard rock type that typically stays stable during excavation. Sandy soil, although it can be tricky due to its tendency to shift when dry, is usually less susceptible to sudden collapse compared to soft clay, which can become exceedingly dangerous without proper precautions.