Slope stability

A previously stable slope can be affected by a number of predisposing factors or processes that make the safety factor decrease - either by increasing the shear stress or by decreasing the shear strength - and can ultimately result in slope failure.

Real-life failures in naturally deposited mixed soils are not necessarily circular but, prior to computers, it was far easier to analyze such a simplified geometry.

At the other extreme, slab-shaped slips on hillsides can remove a layer of soil from the top of the underlying bedrock.

Again, this is usually initiated by heavy rain, sometimes combined with increased loading from new buildings or removal of support at the toe (resulting from road widening or other construction work).

The angle of repose is related to the shear strength of geologic materials, which is relevant in construction and engineering contexts.

It is important for many civil and geotechnical engineers to know the angle of repose to avoid structural and natural disasters.

[5] However, water saturation can result in a decrease in the slope's stability since it acts as a lubricant and creates a detachment where mass wasting can occur.

Smaller surface area also leads to more capillary action, more water retention, more infiltration, and less runoff.

[7] The presence of vegetation does not directly impact the angle of repose, but it acts as a stabilizing factor in a hillslope, where the tree roots anchor into deeper soil layers and form a fiber‐reinforced soil composite with a higher shear resistance (mechanical cohesion).

Vegetation also stabilizes the slope via hydrologic processes, by the reduction of soil moisture content through the interception of precipitation and transpiration.

It is performed to assess the safe design of a human-made or natural slopes (e.g. embankments, road cuts, open-pit mining, excavations, landfills etc.)

[10][11] Successful design of the slope requires geological information and site characteristics, e.g. properties of soil/rock mass, slope geometry, groundwater conditions, alternation of materials by faulting, joint or discontinuity systems, movements and tension in joints, earthquake activity etc.

[15] Choice of correct analysis technique depends on both site conditions and the potential mode of failure, with careful consideration being given to the varying strengths, weaknesses and limitations inherent in each methodology.

A new slope can then be designed in the ‘reference’ rock mass with compensation anticipating further damage due to excavation and future weathering.