incompetent rock

incompetent rock

[in′käm·pəd·ənt ′räk]
(engineering)
Soft or fragmented rock in which an opening, such as a borehole or an underground working place, cannot be maintained unless artificially supported by casing, cementing, or timbering.
References in periodicals archive ?
4) A possible mechanism for deformation of the Gachsaran Formation is flow of salt and of other incompetent rocks (members 2-5).