Search

When tunneling engineers talk on NATM, they often mean different things because some of them define it as a special technique,but others as a sort of philosophy. Recently the scene has been complicated by new terms and even alternative names, when discussingcertain aspects of NATM.The NATM integrates the principles of the behaviour of rock masses under load and monitoring the performance of undergroundconstruction during construction. The NATM is not a set of specific excavation and support techniques. Based on the computationof the optimal cross section, just a thin shotcrete protection is necessary. Additionally, geotechnical instruments are installed to measurethe later deformation of excavation. Therefore a monitoring of the stress distribution within the rock is possible. This monitoring makesthe method very flexible, even at surprising changes of the geomechanical rock consistency during the tunneling work.

A basic element in the decision making process on the adequacy of the support system was a monitoring and analysis process.We consider geomonitoring as continuous monitoring of objects (e.g. of mines, tunnels, machinery, buildings and a lot of constructions)during the construction or operating phase using geodetic, geotechnical and geophysical methods.Geomonitoring is gaining increasing significance as a result of new safety aspects, from the point of view of immission controlas well as in connection with early warning and alarm systems. Specific areas covered include geological and geotechnical explorationsrequired, construction of tunnels and shafts, design considerations, geomechanical analysis, design of linings, and instrumentationand monitoring.Consequently, monitoring of many of the instrument arrays have to continue for several years after construction. Monitoringprograms must be carried out for well-defined purposes, be well planned, and be supported by competent staff through completionand implementation of results from the monitoring program.

The Bôrik Tunnel is located in an evenly forested mountain ridge, which makes up the northernmost part of the Kozie ChrbtyMountains. It borders with the hilly-to-flat Popradská Kotlina. The tunnel Bôrik has been designed such that it complies withthe requirements set for a motorway tunnel with two tunnel tubes, each for one-way motorway traffic. The Project is part of D1Motorway in Slovak republic, connecting Bratislava - Žilina - Prešov – Košice. Tunnel Borik is part of Motorway D1 Mengusovce-Janovce and is direct link to motorway section D1 Važec – Mengusovce.The support classes describe the use of tunnel primary and secondary lining structural elements, on which depends the wholeWorks’ stability. The primary lining constructed includes circumferentially and radially projecting beams in which the reinforcing barsare embedded, whereby a lining having a reinforcing structure can be constructed in a simple and economical mannerand in a shortened construction period. In recent years, it has become popular to spray a layer of shotcrete to serve as the primarylining. The shotcrete is frequently reinforced by steel meshes and, if necessary, braced by steel lattices.At present in underground construction very important role plays the line of mechanical engineering, whitch is necessaryin supporting elements of the primmary and secondary lining.