angle of rest

(engineering) The maximum slope at which a heap of any loose or fragmented solid material will stand without sliding, or will come to rest when poured or dumped in a pile or on a slope. Also known as angle of repose.

The maximum angle with the horizontal at which a mass of material, as in a cut or embankment, will lie without sliding; the angle between the horizontal and the maximum slope that a soil assumes through natural processes.