Investigation on the efficiency of different methods for evaluation of ground settlement due to excavation of Tabriz metro tunnel, line 2

Document Type : Research Article

Authors

1 Department of Civil Engineering, Seraj Institute of Higher Education, Tabriz, Iran

2 Department of Mining Engineering, Faculty of Engineering, Urmia University, Urmia, Iran

Abstract

Mechanized shallow tunnelling in urban areas and soft grounds leads to horizontal and vertical displacements at the host materials of the tunnel and causes the ground settlement due to tunnelling which can have undesirable and even destructive impacts on surface structures and subsurface Facilities. In the present study, ground settlement induced by the mechanized excavation of Tabriz Metro tunnel, Line 2, is considered as a case study using semi-experimental, analytical and numerical methods, and the impact of different factors will be investigated. For this purpose, a section of the studied tunnel was selected for evaluating the settlement via mentioned three methods, and the results were analyzed and compared with the real settlements, measured during the tunnel excavation. The results show that the semi-empirical method releases relatively higher values of settlement because of intrinsic and fundamental specifications of the method while the analytical and, especially, numerical methods generally provide logical and reliable outcomes because of the utilization of more parameters of tunnel and host soil such as geotechnical characteristics of host soil and geometrical properties of the tunnel. In this regard, to emphasize the valuable capabilities of numerical methods, the effect of several factors on the amount of settlement was studied via FLAC 2D software. The outcomes showed that the ground settlement increases when the elasticity modulus of grout and the elasticity modulus of soil decrease as well as when the surface load increases and the groundwater level is dropped.

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