ABSTRACT
This paper analyses the load-bearing behaviour of pipe umbrellas by means of 3D numerical calculations considering the interaction among pipes, ground, temporary support and face reinforcement or improvement. With the purpose of validating a numerical model, data from an in-place chain-inclinometer in a Swiss tunnel is evaluated and interpreted numerically. The limitations of the measurements and potential sources of error in the evaluation of the monitoring data are discussed. The numerical simulation results map the observed pipe behaviour reasonably well. Face reinforcement or improvement is found to considerably affect the ground deformations ahead of the tunnel face and thus also the loading of the pipes. Furthermore, the numerical analyses indicate that the degree of structural utilization of the pipes is rather low in the present tunnel case, meaning that safety against failure is high and confirming the applied simplified design models to be conservative.
