Shotcrete-Technology ´06

Structural design of temporary shotcrete tunnel linings under consideration of
physically nonlinear material behaviour wth special reference on the new
German Standard DIN 1045-1

Prof. Dr.-Ing. Karl Schikora, Dr.-Ing. Bernhard Thomée, Fachgebiet für Baustatik, TU Munich, Germany

In the case of shotcrete methods the tunnel section is driven in recurring construction phases and subsequently supported by shotcrete. This results in a three-dimensional load carrying behaviour of the surrounding soil where the stress state changes with each excavation phase. At a distance from the heading of one to two times the tunnel diameter things are different. Here the load carrying behaviour is approximately plane. This knowledge can be used to develop a computational model that simulates the excavation process by a plane strain problem. Determining the stress resultants in the tunnel lining, using a physically nonlinear analysis according to German standard DIN 1045-1, shows that the bending moments at the ultimate limit state will decrease due to cracking to a value not exceeding moments under service load. This result can be used to determine the load bearing capacity of the tunnel lining from the stress resultants in the serviceability limit state without performing an expensive nonlinear analysis.