Subsection 1: Landslides and falling rocks.

In all underground structures, the risks of landslides or falling boulders are prevented, using methods appropriate to the height of the structure: 1° Either by means of a supported or suspended support and a lining appropriate to the nature of the ground; 2° Or by means of monitoring, probing and methodical purging of the facing and crown.

The walls of shafts and underground galleries, the roofs of the latter, as well as any consolidation work carried out or support systems put in place, are examined: 1° Upon resumption of each work shift, over the entire height of the shafts and over the entire length of the galleries; 2° After each blast, over a length of at least 50 metres behind the blast face. These examinations are carried…

When an underground shaft or gallery is to be lined with masonry or concrete, the elements of the support system are removed only as the work progresses and only insofar as, having regard to the stability of the ground through which the work is to be carried out, such removal cannot be detrimental to the safety of the workers. Similar precautions are taken when carrying out lateral felling and backfilling…