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Hofmann K.,Tiefbauamt | Schmitt D.,Beratende Ingenieure fur Grundbau und Felsbau GmbH | Wittke W.,Beratende Ingenieure fur Grundbau und Felsbau GmbH
Geotechnik | Year: 2010

The planned Rosensteintunnel is part of the development of the main traffic artery B10 in Stuttgart. The planned two tube tunnel runs under the Rosensteinpark and the grounds of the Wilhelma Zoo. The two tubes both with two lanes per direction will be constructed by mining method for approximately 750 m and per cut and cover method for approximately 250 m of length. It is planned to use geothermal energy to heat and cool the operation rooms. According to a feasibility design of the geothermal facility, the use of geothermal energy in the tunnel is economical and can be achieved at comparatively low cost and effort. To verify this, the thermal conductivity of the ground was evaluated with the aid of "thermal response tests". The results of these tests were back analyzed by means of heat transport analyses according to the finite element method. In this way, the analysis model could be calibrated.

Erichsen C.,Beratende Ingenieure fur Grundbau und Felsbau GmbH | Wittke W.,Beratende Ingenieure fur Grundbau und Felsbau GmbH
Geotechnik | Year: 2010

Successful construction means an economic design, a building according to standards, no cost overrun and completion in time. Successful construction in jointed rock requires a comprehensive exploration and an adequate description of the rock mass as well as a quantitative consideration of the stress-strain behavior and - if the construction takes place under the groundwater level - of the water permeability of the rock mass. Stability analyses have to take into account the stress-strain behaviour, the seepage and the interaction between structure and rock. The results of early phases of design are the basis for tendering and construction. Therefore the early design should be carried out to an adequate extent and with high quality. Modifications of the design during construction usually lead to cost overrun and delays in construction and therefore should be avoided.

Different views exist with regard to the design of support systems for tunnels. The description of the ground with the aid of realistic rock mechanical models and stability analyses in which these models are implemented have proven to be particularly successful for the design of structures in rock. A design on the basis of a rock mechanical model and an adequate analysis procedure is economic and save provided that there is sufficient experience available with respect to the development of rock mechanical models, the corresponding mechanical parameters, the performance of stability analyses and the check of their results during construction with the aid of monitoring. Since several decades, the proponents of classification systems attempt to develop design methods on the basis of rock mass ratings which are suitable for practical use. However, the application of these classification systems involves risks, since these systems reveal substantial deficiencies which often lead to an unsave and uneconomic design. Using these systems, the rock mass properties are described by one single value and parameters having a decisive influence on the required safety measures are not or only insufficiently considered. As a consequence, the complex rock mass behavior is oversimplified and the assessment of the rock mass properties is ambiguous.

Wittke M.,Beratende Ingenieure fur Grundbau und Felsbau GmbH | Wittke-Gattermann P.,Beratende Ingenieure fur Grundbau und Felsbau GmbH | Wittke W.,Beratende Ingenieure fur Grundbau und Felsbau GmbH
Geotechnik | Year: 2010

In the past, large heavings of the invert and damages of the internal lining frequently occurred in tunnels constructed in the gypsum Keuper containing anhydrite. Therefore, WBI has developed an analysis procedure in which the models describing the stress-strain behaviour, seepage flow, water uptake and swelling are coupled in order to allow a safe and economic design of tunnels in swelling rock. This analysis procedure was calibrated on the basis of test results and back analyses of monitoring results. As shown in this paper by means of analysis results, the swelling pressure acting on a tunnel's internal lining designed according to the principle of resisting support, remains limited, if the tunnel is driven at a considerable distance to the water-bearing, leached rock mass overlying the swelling rock. This is due to the existence of a tight zone at the transition from the leached rock to the swelling rock which keeps the rock mass dry to a large extent. However, if a tunnel is located in this transition area, water may seep into the tunnel and the swelling process will be initiated. As a consequence, heaving of the invert and in case of insufficient dimensioning of the internal lining damages may occur. This can be verified by means of a number of case histories. It therefore is concluded that a tunnel in swelling rock should be driven at a considerable distance to the leaching front. Otherwise displacements due to swelling and large swelling pressures acting on the internal lining are to be expected. In both cases, the analysis procedure developed by WBI is a powerful tool to enable a safe and economic design.

Wittke-Schmitt B.,Beratende Ingenieure fur Grundbau und Felsbau GmbH | Schmitt D.,Beratende Ingenieure fur Grundbau und Felsbau GmbH | Wittke W.,Beratende Ingenieure fur Grundbau und Felsbau GmbH
Geotechnik | Year: 2010

During excavation of a tunnel in jointed rock with a shield machine, rock blocks may fall from the temporary face, the sidewalls and the roof, if the tunnel contour is not stable. In such cases, the temporary face and the tunnel contour in the shield area must be stabilized. For this purpose, an earth pressure balanced shield (EPB shield) can be applied. However, this requires that the excavated rock can be transfered into an earth mud which is able to support the temporary face. This is not always possible. Therefore, the existing rock must be investigated in this regard before the decision on the TBM type is taken. In the given paper, a test is presented which is able to simulate the processes in the excavation chamber of an EPB shield in a comparatively realistic way. Moreover, a conceptual model is elaborated for the evaluation of the conditionability of the investigated rock on the basis of the test results. For a large number of preliminary investigations, a simple pilot test can easily be carried out. In addition, mineralogical investigations, slake durability tests and soil mechanical tests should be carried out.

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