A landslide is defined as the rapid movement of landmass over a slope. When a natural slope or man-made slope becomes unstable, a landslide results. The main causes of landslides are:
- groundwater table changes
- earthquakes or other vibrations
- construction on top of slope, etc.
(Courtesy Huge Landslide)
The resistance to a landslide is offered by the type of soil and the geometry of the slope. Preventive and remedial measures include modifying the geometry of the slope, controlling the groundwater, constructing tie backs, spreading rock nets, etc.
Although landslides may not be preventable, their devastating effect on humans and their property is avoidable and can be mitigated.
For this post, let us discuss landslide causes in detail.
The basic cause of a slope failure is when the driving forces (forces causing the downward movement) exceed the resisting forces. When heavy rains occur, the rain water infiltrates into the soil and groundwater table is raised. The pressure exerted by the water thus increases, causing the driving force to exceed the resisting force, hence resulting in a landslide. In an extreme case, the soil may become so saturated with water, that it behaves as a fluid and flows downwards. This is called a mudslide.
(Courtesy Daily Bruin)
Earthquakes cause vibrations and ground shaking, which induce landslides. Other man-made vibrations such as movement of traffic, opertions of heavy machinery, pile driving and other construction-related vibrations may also cause landslides. Particularly, if these man-made vibrations occur on top of the slope, a landslide could be triggered.
(Courtesy Landslide at Kobe)
Copyright Kshitija Nadgouda.