The demand for efficient new infrastructure systems is increasing and automatically leads to the underground as living space above ground is becoming more and more scarce. This also applies to the mechanical construction of tunnels, which is almost completely carried out in underground thanks to the tailor made tunnelling technology made by Herrenknecht. Mechanized tunnel excavation has entered new dimensions in terms of size, length, geological complexity and depth of underground constructions. It sets the standards regarding safety, profitability and environmental protection – in Traffic Tunnelling projects as well as in the trenchless construction of Utility Tunnels, such as sewer, water, cable tunnels and oil and gas pipelines. Different machine types and working principles have been developed to master the geological and hydrological requirements of tunnelling projects worldwide. This paper gives an overview on state-of-the-art hard rock tunnelling equipment and project possibilities but will also highlight the innovative and current design approaches to overcome the difficult specific project conditions of hard rock projects of today. Reference projects and experiences world wide show the feasibility of tunnel visions and the infrastructure importance for the respective area.


The tunnel projects of today are increasingly constructed in more complex conditions. In soft ground the current challenges are projects in heterogeneous soil conditions, tunnel construction in urban areas with low overburden and conditions with very high ground water pressures above 10 bar. In hard rock the project demands are characterized by long tunnel drives, high overburden and abrasive rock masses such as the conditions faced with the project for the rail crossing of the Alps in Switzerland, the Gotthard Base Tunnel. These high standards on tunnel projects also demand safe and economical tunnelling technology which is provided by mechanized tunnelling. In hard rock tunnelling there are, depending on the rock quality, two groups of hard rock tunnel boring machines. The Gripper TBMs are used in solid rock conditions and the Shielded TBMs (Single or Double Shielded TBMs) are used in stable and unstable rock conditions. The success of each tunnelling system depends on the excavation process, the rock support concept and the mucking system and logistical system of the applied technique. The following chapters give an overview of these hard rock tunnelling systems and will focus on representative project examples.

Hard Rock tunnelling systems
Gripper TBM

This machine type is typically used in stable and massive rock conditions with low water ingress. The cutterhead of the Gripper TBMs is a flat face design. It is equipped with disc cutters to suit the rock conditions. Buckets which are arranged at the circumference of the cutterhead are responsible for the removal of excavated 754 material. They are supported by additional backscrapers on the rear side of the cutterhead. In addition to drilling technology, efficient and economical material transport is also a key requirement for successful TBM tunnelling.

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