Geotechnical, structural and geodetic measurements for conventional tunnelling hazards in urban areas – The case of Niayesh road tunnel project

Abstract

Tunnelling is increasingly being seen as an environmentally preferable means of providing infrastructure such as transportation and utilities to densely populated urban areas. It is often cost-effective as an alternative to surface solutions, when the risk and cost of disruption during construction is taken into account. When excavation is conducted to lead underground connections such tunnels and galleries, the ground level is subject to subsidence impacting the infrastructures such as buildings, bridges, pipe lines and roads. Therefore a monitoring system is required to control the risk on the tunnel influence areas.In this research firstly tunnelling hazards in urban areas are introduced, and then the importance of monitoring during conventional urban tunnelling is presented. Finally the characteristics, limitations, problems, hazards and remedial measures for Niayesh road tunnel project were introduced. The Niayesh tunnel is under construction in urban area in Tehran, Iran. It was shown that the tunnelling in urban area has some major and particular characteristics and constraints compared with rural area which must be considered in the design and during construction of these types of infrastructures. The importance of geotechnical/structural/geodetic instrumentation as a practical engineering tool for systematic monitoring of tunnels and buildings in urbanized areas were shown and layout of Niayesh tunnel monitoring plan considering all requirements were planned and implemented. Based on monitoring results probable alerts, possible counter-measures and several design optimizations were given.