Geotechnical Investigations

Geology plays a dominant role in many major decisions made in designing and constructing a tunnel, from determining its feasibility and cost to assessing its performance. In tunnels, unlike other structures, the ground acts not only as the loading mechanism, but as the primary supporting medium as well. When the excavation is made, the strength of the ground keeps the hole open until supports are installed. Even after supports are in place, the ground provides a substantial percentage of the load-carrying capacity. Thus, for the tunnel designer and builder, the rock or soil surrounding a tunnel is a construction material. Its engineering characteristics are as important as those of the concrete or steel used in other aspects of the work.