Abstract
Tunneling in urban areas, has raised the level of difficulty and challenge in respecting the constraints deriving from human presence and, therefore, the necessity for the study of geological and geotechnical properties and parameter, classification of the soils according to their engineering behavior, choosing the right TBM, determine groundwater level and determining possible geological hazards. In this paper some geological and geotechnical study took place along the tunnel route. This investigation is done by the result of 73 machinery borehole and 32 manual borehole that took place in the process of studying the tunnel route and continued by the result of field tests and laboratory tests and according to the result, the geological zone classified in 6 zone in tunnel route; due to the result of Cerchar abrasivity test and since Alluvial soil is the main soil in most of the tunneling route, the excavation soil classified as highly abrasive. In some part of tunneling there is a risk of clogging due to the high amount of clay. Based on the results of Lofran tests the permeability of most of the classified soils in route of the tunnel was obtained less that 10E-7 m/s.
Highlights
The north-south section of Tehran Metro Line 7 begins on the mountain road (West Side) near the Yadgar Imam highway in northwestern Tehran, and continues east-westward to the Cave Field
By studying the soil units, the ET-1 line was not suitable for drilling with the Earth Pressure Balance (EPB) machine, and it is necessary to improve the parameters of the soil by using arrangements such as adding foam, polymer and fine mineral materials especially in presence of high pressure water
According to the geological engineering section of the tunnel engineering as well as Table 4, units ET-2, ET-3 and ET-5 are respectively the most widely spread in the tunnel path, and ET-1, ET-4 mostly developed as lenses of sand and gravel lenses
Summary
The north-south section of Tehran Metro Line 7 begins on the mountain road (West Side) near the Yadgar Imam highway in northwestern Tehran, and continues east-westward to the Cave Field. The tunnel route in the Hemmat highway with torsion to the east along the Chamran highway and Navab highway to the intersection of Qazvin Street continues and connects to the easternwestern part at 7N station. Accurate and comprehensive identification is necessary in order to understand the geotechnical position of the road along the route and to investigate the hazards caused by the existence of some natural and artificial factors.
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