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 ?
Poor working conditions inside coal mines in Balochistan claim the lives of miners on an almost daily basis in Harnai, Sowrange, Dukki, Mach and other parts of the province, but often go unreported.Coal mining is considered much more hazardous than hard rock mining due to flat-lying rock strata, generally incompetent rock, leakage or explosion of poisonous gases and coal dust, collapsing of mine stopes or general mechanical errors from improper use and malfunctioning of mining equipment, it added.
The major cause of the slump and earth flow in the investigated area is because of water saturation in the regolith Gharbina meandering stream and the underlying incompetent rocks of the Kurram Formation/group.
(4) A possible mechanism for deformation of the Gachsaran Formation is flow of salt and of other incompetent rocks (members 2-5).