Tunneling and underground engineering are an essential part of modern construction. They not only help us break through geographical barriers, but also provide many conveniences for human life.
What are tunneling and underground engineering?
Tunneling and underground engineering encompass the construction of passages and various underground structures within rock masses or soil. These structures include railways, roads, canal tunnels, underground railways, and underwater tunnels, all designed for transportation purposes. Additionally, underground works serve municipal, air defense, mining, storage, industrial, and civil production needs. Military applications involve the creation of national defense tunnels, while underground power plants support water conservancy and power generation projects. Various water tunnels are also part of this extensive domain. These projects are planned, surveyed, designed, constructed, and maintained through research and construction, a branch of civil engineering.
Construction methods of tunneling and underground engineering
The construction methods of tunneling and underground engineering include the cut and cover method, undercutting method, immersed tube method, pipe jacking method, and the new Austrian tunneling method.
- The cut-and-cover method is mostly used for constructing shallow tunnels or urban railway tunnels. In this process, construction begins with digging foundation pits or trenches into the ground. Subsequently, the lining is built, followed by backfilling to complete the structure.
- The undercutting method is constructed by digging holes underground. The mining method and shield tunneling method are both underground excavation methods.
- The immersed tube method is a construction method for building tunnels underwater. Tunnels built using this method are called immersed tube tunnels.
- The pipe jacking method is an underground excavation construction method used when tunnels or underground pipelines pass through various obstacles such as railways, roads, rivers, or buildings.
- The new Austrian tunneling method employs the principles of rock mass mechanics theory. It centers on preserving and leveraging the inherent self-supporting capability of the surrounding rock. Rock bolts and shotcrete are used as the primary means of support, offering timely reinforcement to manage the deformation and relaxation of the surrounding rock. It makes the surrounding rock an integral part of the support system and guides the methods and principles of tunnel construction and underground engineering design and construction through the measurement and monitoring of the surrounding rock and support.
In conclusion, the construction process of tunnel and underground engineering is realized through two steps of excavation and support, no matter which construction method is chosen, in addition to considering the geological conditions of the project, environmental requirements, engineering requirements, and other factors, it is also very critical to choose the right construction tools.
Construction tools for tunneling and underground engineering
The construction tools for tunneling and underground engineering are mainly rock drilling tools and rock bolts. Rock drilling tools are used for excavation, while rock bolts are used for support.
Application of rock drilling tools in tunneling and underground engineering
In the past, the rock drilling and blasting technology used in tunnel excavation and shaft engineering excavation was a shallow hole rock drilling and blasting method. Rock drilling tools used were air-leg light rock drills and H22mm tapered drill rods, 38-42mm chisel bits and four-tooth and five-tooth button bits. From the point of view of drilling and blasting rock drilling technology, this way of tunneling is not only slow and inefficient but also easy to causes damage to the rock when blasting. At the same time, the labor intensity of the construction personnel is high, the working conditions are harsh, and the working safety environment is poor. Therefore, it is a construction method that has long been eliminated in industrially developed countries.
Nowadays, the development direction of rock drilling in tunnels and shafts is to use hydraulic rock drilling rigs, full-face tunnel boring machines and raise drilling rigs for mechanized construction. The main rock drilling tools used are R/T38-H35-R32 structure with lengths of 3090 mm, 3700 mm, 4310 mm, 5525 mm drill rods and diameters of φ45 mm, φ48 mm, φ51mm, φ54 mm with seven and nine tooth button bits, R32-H28-R28 structure with lengths of 2700 mm, 3050 mm drill rod for coal and rock roadway drill jumbo, diameters of φ41 mm, φ43 mm seven-tooth button bits, etc.
Application of rock bolts in tunneling and underground engineering
The supporting effect of rock bolts mainly depends on the adhesion strength and shear strength between the rock bolt and the surrounding rock. To improve the adhesion and shear strength of rock bolts, measures such as appropriately increasing the diameter of rock bolts (increasing the adhesion area), appropriately changing the surface shape of rock bolts can be used.
Rock bolts are effective due to the deformation and sliding of surrounding rocks, generating tensile and shear forces. But in soft surrounding rocks showing continuous dynamics and medium-hard rocks with developed joints, the stresses generated in rock bolts are different because of different deformation patterns.
Except for excavation and support operations, other operations are auxiliary, such as transportation, drainage, ventilation, measurement, geological forecasting. However, these operations are also the key to the success of the support and cannot be ignored.
The emergence of tunnels and underground engineering has changed people’s perception of space, and this transformation is inseparable from the support of rock drilling tools. By using rock drilling tools, people not only improve the efficiency of excavation but also reduce the labor intensity of workers, providing unlimited possibilities for our development in underground space. Looking ahead, we anticipate witnessing further innovations and applications in rock drilling tools aimed at more effectively supporting the advancement of human society.
