Rock Tools in Tunnelling

Introduction

A tunnel is an engineering building buried in the ground, a form of human use of underground space. Tunnels are divided into traffic tunnels, hydraulic tunnels, municipal tunnels, mine tunnels, and military tunnels according to the function of use. The structure of the tunnel includes two parts, the main building, and the auxiliary equipment. The main building consists of cavern body and door. Auxiliary equipment includes the shelter, fire fighting facilities, emergency communication and drainage prevention facilities, and special ventilation and lighting equipment for long tunnels.

Tunnel Excavation and Support

Tunnel construction is a process of stress release and stress control. This process is usually achieved through two steps of excavation and support. That is the original state of the surrounding rock – excavation – support – the formation of long-term stable structures.

The so-called control technology here refers to how to control the deformation within the allowable range during excavation and support and ensure the long-term stability of tunnel structural system.

Excavation is the method of releasing stresses, and the process and degree of stress release vary with different excavation methods.

Support is a method of stress control, and similarly, the process and degree of stress control differ for different support methods.

Application of Rock Drilling Tools in Tunnelling

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 Tunnelling

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.

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