Daylight Envelope

Where a plane dips at a flatter angle than the face, it is said to "daylight" on the face and has the potentially for sliding. Conversely,where a plane dips more steeply than the face, it does not daylight and sliding is not possible .

Similarly, where a discontinuity set dips into the face, it is not possible for sliding to occur, but toppling is possible. The position of these poles in relation to the slope face may show that the poles of all planes that daylight (and are potentially unstable) lie inside the pole of the slope face. This area is known as the Daylight Envelope and can be used to quickly identify unstable blocks. *

A daylight envelope is a useful indicator of bench or slope stability, as poles that lie within the daylight envelope could be considered as potentially unstable. This information can be supported with the implementation of a friction cone to further highlight the stability levels of the encapsulated poles. You can add a friction cone using the Cones tab.

*Information derived from Rock Slope Engineering: civil and mining; Duncan C. Wyllie, Christopher W. Mah, Evert Hoek.