عنوان مقاله [English]
Nowadays, the necessity of implementing the underground structures in the urban areas has been increased due to the continuous increase of the spaces needed for intra-urban transports. The road and metro tunnels are among the underground spaces mostly considered in the cities. As the cities are mainly located on the soft and alluvium grounds, some difficulties associated with implementing underground spaces in these grounds may be arised. The most important difficulties in this regard are the settlement of the ground surface during construction and its effect on the surrounding structures.
The construction of large section underground spaces such as metro lines stations is essentially important. One of the factors in this regard that should be considered in the urban areas is to select the method of excavating the spaces. This fact has significant effect on the stability of surrounding tunnel spaces during excavation, surface settlement due to the excavation and long term stability of excavated space (e.g. metro station).
Methodology and Approaches
In this research, three methods including pre-supporting concrete arc, side galleries and German method have been studied and evaluated for implementing the underground stations concerning the stability of space, surface displacement of the tunnel and the settlements due to the excavation. In the other words, this research mainly focuses on the effect of using different excavation methods (with or without supporting structure) on the superficial displacements of the tunnel, settlement of ground surface and other parameters. Then, the proper method is suggested for excavating the considered station. The numerical modeling of different methods for implementing the space has been conducted using finite element method and Plaxis 3D software.
Results and Conclusions
The results obtained in this research indicate that the maximum settlement of the ground surface is seen in the side galleries and its minimum in the pre-supporting arc methods. Moreover, at the end of implementation of the first floor of the station, the settlements of ground surface have been very similar in the concrete arc and German methods. It means that these two methods can be used in the one- floor stations.