How does rock mechanics help engineers better understand how rocks will react to tunneling projects?

Tunneling into rock is a relatively complex process, requiring careful project planning and analysis of site conditions. While rock may seem solid, it contains numerous cracks, fissures, faults, folds, and discontinuities, all of which can trigger tunnel collapse.

In addition to the faults and discontinuities mentioned previously, the physical condition of the rock, the number and type of layers, their orientation (strike and dip), water table elevation, etc., all affect the mechanical properties of the rock formation, which in turn influence the feasibility, trenchless construction methods, and stability of the tunnel design.

Rock mechanics, as its name suggests, is the study of the mechanical behavior of rocks and rock masses. It is a theoretical and applied science field that is concerned with how rock structures respond when subjected to various forces in their physical environment.

In terms of engineering applications, it specifically deals with the design of structures built in, around, or from rock. In addition to civil engineering and construction, rock mechanics is commonly used in other industries, such as mining, nuclear and petroleum engineering.

Geological Engineering professionals who specialize in rock engineering and tunnel design typically use a variety of numerical and 3D analysis, geological tools, and fundamental principles to assess rock properties and behavior to design safe and economical tunneling solutions.

These tools, combined with testing of in-situ stress conditions, allow engineers to approximate the stresses present in the rock and determine any potential strains which may arise due to tunnel excavations. Once the appropriate analyses have been performed, engineers can establish the following:

• The overall feasibility of the tunnel project given the properties of the existing rock properties.
• The estimated cost of the project, taking into consideration various factors, such as time, labor and permanent/temporary structural supports.
• The types of stability measures required.
• The optimum geometry and dimensions of the tunnel based on the properties of the rock.