EPB tunneling challenges in bouldery ground: a new experience on the Tabriz metro line 1, Iran

Underground construction of the Tabriz metro line 1 involved boring twin tunnels with two earth pressure balance machines in alluvial deposits. Although this type of machine is recommended for excavation in fine soils, its performance was evaluated in this project where part of the ground consists o...

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Bibliographic Details
Published in:Bulletin of engineering geology and the environment 2014-05, Vol.73 (2), p.429-440
Main Authors: Barzegari, Ghodrat, Uromeihy, Ali, Zhao, Jian
Format: Article
Language:English
Subjects:
Alluvial deposits
Boring machines
Drilling & boring machinery
Earth and Environmental Science
Earth pressure
Earth Sciences
Environmental risk
Excavation
Foams
Foundations
Geoecology/Natural Processes
Geoengineering
Geological engineering
Geology
Geotechnical Engineering & Applied Earth Sciences
Grounds
Hydraulics
Laboratories
Landslides
Nature Conservation
Original Paper
Overburden
Permeability
Rock
Shear strength
Soil conditioners
Soils
Subways
Tunnels (transportation)
Underground construction
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Summary:Underground construction of the Tabriz metro line 1 involved boring twin tunnels with two earth pressure balance machines in alluvial deposits. Although this type of machine is recommended for excavation in fine soils, its performance was evaluated in this project where part of the ground consists of alluvial deposits with particle size ranging from silt to boulder and even rock blocks. It was found that the tunnel boring machine (TBM) performance was highly reduced due to the variation in ground conditions. Many types of problem were observed during the excavation in coarse grained alluvial deposits including high cutter-head torque, excessive wear of tools, breaking of TBM parts and ground instabilities in the form of large settlement and ground collapse. A trial effort was implanted to stabilize the overburden ground by the injection of cement grout, but this proved to be unsuccessful. In both cases, the excavation operation was delayed. With the experience gained from the excavation of the first tunnel and use of foam with a high foam expansion ratio as a soil conditioner in closed mode, the performance of the TBM in the second tunnel improved.
ISSN:1435-9529
1435-9537
DOI:10.1007/s10064-013-0490-7