The increased use of pipe roof umbrella systems as a pre-support method necessitates the need for a standardized approach to determine the basic design parameters during design. The knowledge gained by in situ measurements using in place inclinometer chains were used to identify key influencing factors and guide 3-D numerical investigations. These simulations acknowledged and advanced the geotechnical model based on the in situ measurement data. Due to this it is possible to calculate the estimated deformations and to determine the design parameters of a pipe roof umbrella system with numerical simulations. To control the ground ? support interaction and adapt the support to the actual rock mass quality the developed measurement system can be additionally used in sections that are very sensitive to subsidence. Using this knowledge an appropriate modeling scheme allows the determination of the required support. With a continuous adaptation of the support system to the encountered ground behavior during construction a safe end economical construction process is assured.
The modernization of urban, as well as regional infrastructure has resulted in increased tunneling activities in soil and weak rocks within developed areas. A safe and economical construction is always desired even though the conditions of the ground may not be optimal. This often results in critical sections, especially in urban areas, being supported with cost intensive and time consuming pre- support systems like freezing or jet grouting to protect surrounding infrastructure from damages.
Over the last decades technological developments have led to the increased use of different presupport technologies to help prevent undesirable events. The pipe roof support method is one of the pre-support concepts that nowadays is much used in conventional tunneling and has even been included in TBM support systems. This method of supporting potentially unstable ground ahead of the face provides a high degree of flexibility and can be easily adapted to the encountered conditions. However, in our opinion there is a significant lack of knowledge about the ground?support interaction associated with this method and thus objective design criteria are currently not available.
In order to obtain a better understanding of this support system, in situ measurements with inclinometer chains installed parallel to the pipe roof support were performed. The measurements of the inclinometer chain were linked to the geodetical displacement measurements taken inside the tunnel and on the surface. These measurements display the longitudinal distribution as well as the magnitudes of the settlements in the crown region of the excavation area [1].
Laboratory investigations on the rock mass materials and the pipes were performed to develop input parameters for numerical simulations. With this study a geotechnical model and the way to transfer it into a numerical model is investigated.
