Technical note: Geotechnical conditions and hazards of urban tunneling in Tehran, Case Study: Motevaselian Tunnel

Engineering Geology and geotechnical parameters assessment is of the most important issues in successful tunnel design and construction operation. In urban areas, exact and complete reconnaissance of these parameters and site investigations are more critical as a result of the intensified effect of settlement and failure of the tunnels. Geotechnical parameters and hazards in tunnel route also affect the tunnel boring machine (T.B.M) selection and so they are challenging and very important issues. Shahid Motevasselian tunnel with a length of 10 Km. connects Shahid Sayyad Shirazi highway south wards (from north of Sepah Sq.) to Azadegan highway. There is a high geological diversity in geological units as a result of North- south direction of the tunnel and so it is too complicated to assess the parameters. In this study, as a good experience, the method of dealing with the complexities to achieve a reliable assessment of geological and geotechnical conditions is considered and also the possible hazards in different parts of the tunnel is determined. According to the geological and geotechnical situation, tunnel rout is divided to 3 distinct parts (northern part, middle part and southern part) and introducing the different soil types in terms of Geotechnical parameters, range of different parameters in any soil type is determined by combining the results of field and laboratory investigations, and finally, the material properties of each soil type determined as well as possible hazards likely in different parts of the tunnel route.