What are the factors that affect the stability of earthwork slopes?

1. Factors affecting slope stability: After the excavation of a foundation pit, the collapse of the slope occurs when the shear stress within the soil of the slope exceeds the soil’s shear strength. The shear strength of soil, in turn, derives from the internal friction and cohesion of the soil. Therefore, anything that can affect the shear stress, internal friction, and cohesion in the soil can influence the stability of the slope. (1) Influence of soil category. Different types of soil have different internal friction and cohesion. For example, sandy soil has zero cohesion and only internal friction; it is this internal friction that maintains the stable equilibrium of the slope. Clay soils, on the other hand, possess both internal friction and cohesion; therefore, the maximum slope at which slopes made of different types of soil can remain stable varies. (2) Influence of the degree of soil wetting. The higher the water content in the soil, the greater its wetness, which leads to a lubricating effect between the soil particles, resulting in a decrease in both internal friction and cohesion. The shear strength of the soil decreases, making the slope prone to instability. At the same time, the increase in moisture content raises the self-weight of the soil, generating hydrostatic pressure in the cracks and increasing the shear stress within the soil. (3) The influence of climate softens the soil; processes such as freezing and thawing in winter, along with weathering, can also reduce the shear strength of the soil. (4) The effect of additional loads or external forces on the slope of the foundation pit can increase the shear stress in the soil, sometimes even exceeding the soil’s shear strength, which causes the slope to lose stability and collapse.