What is the depth threshold, in meters, above which work in unstable ground requires support?

• A. 1.0 meters
• B. 1.5 meters
• C. 2.0 meters
• D. 2.5 meters

Answer: (B)

The depth at which unstable ground must be supported is determined by the increasing risk of rock falls and collapses as you go deeper. As overburden pressure grows and weaknesses in the ground—such as joints, fractures, or loose material—become more influential, supports are needed to keep the excavation safe. In this context, 1.5 meters is the threshold above which working in unstable ground requires supporting the face or sides. Installing timber, steel supports, rock bolts, or other stabilization methods beyond this depth helps prevent collapses and protects workers. The shallower depths listed are not the standard point at which support becomes required, and deeper thresholds would generally imply even more stringent stabilization needs.