Ground support and underground Engineering are important aspects of building infrastructure. They help to control displacements within an excavation and protect structures.
These supports include liner-plate tunnels, full-face method of advance, Mechanical rock bolts, and sound-wall blasting. To understand how these supports work, it is helpful to understand the primary support and secondary support.
Ground support is an essential part of any major underground engineering project, such as the construction of roads, railways, or tunnels. Without reliable ground support structures, the underlying earth, rock layers, and can quickly erode due to heavy traffic or exposure to moisture, compromising the stability of a structure and potentially leading to serious accidents.
In order to maintain strong and stable ground support, engineers typically use a combination of techniques including bulk compaction, anchored material lagging panels, deep foundations, grouting, shotcrete reinforcement systems, anchor rods and cables, soil nails, and geocell walls.
Whether building a new subway line to connect different neighborhoods in a city or creating an underground highway system for easy access between suburbs and urban areas, a robust ground support system is key to ensuring safety and long-term success.
Liner-plate tunnels are an effective and reliable way to support ground during underground engineering and construction. This method uses steel lining to distribute the load. The ring of liner plates is shaped to deflect outward and inward when a load is applied. This deflection is resistive and the force developed is balanced between the lining and the surrounding ground.
Full-face method of advance
The full-face method of ground support and underground engineering involves excavating the entire tunnel diameter. This method is most suitable for tunnels with strong ground. It is also a good option for smaller tunnels. The top-heading-and-bench method, on the other hand, involves excavating a smaller tunnel (called a top heading), then immediately below it a bench excavation. This way, the engineers can gauge the stability of the rock.
Mechanical rock bolts
Mechanical rock bolts are an effective ground support system used in various construction projects. To design a mechanical rock bolt system, engineers need to have a good understanding of the geological characteristics of a given area. They also need to decide on the strength and type of support required. Once the desired strength is determined, engineers will determine the diameter of rock bolts, the suitable rock drill bits, and the spacing between them. Additional reinforcements may also be required.
In underground projects, the geometrical constraints and boundary conditions are not identical to those on the open ground, and this makes the design of blasting techniques for underground structures extremely complex. As a result, the PPV of the sound-wall blasts for underground structures differs from those of surface blasting. The lack of a mechanical model and formula for describing the PPV of underground sidewalls has limited the field of research.
Mesh and screens
Mesh and screens are used in underground engineering and ground support applications to protect against ground collapse. They can be made of welded wires or chain-link for better contouring. They are also used to prevent smaller rocks from falling during excavation.
Long timber members
Long timber members are a versatile type of ground support. They can be used in the construction of underground structures to hold up a rock mass. They can be either forged or threaded. The threaded end allows for adjustment to the rock face and provides more flexibility. Forged ends are less flexible and have limited flexibility.