What is the most common factor leading to slope instability?

The most common factor leading to slope instability is the removal of lateral support. This occurs when materials that provide structural integrity to a slope, such as soil, rock, or vegetation, are removed or eroded, causing the slope to lose its stability. The lateral support is essential for holding the mass of the slope in place; without it, gravity can start to overpower the cohesion and frictional forces that keep the materials stable, leading to landslides or slope failure.

Factors like excessive rainfall, soil saturation, and earthquake activity can certainly contribute to slope instability, but removing lateral support is often the primary trigger. For instance, when trees are cut down or when excavation is performed, the lateral support is diminished, and the slope can become more prone to failure. Recognizing the significance of lateral support removal aids in understanding the primary mechanisms behind slope dynamics and is crucial for effective land use planning and engineering practices.