Investigations on Geotechnical Aspects for TBM Specification on the Tabriz Metro Line 3, Iran

Abstract

In order to perform a successful mechanized tunnelling, detailed surface and subsurface investigations on ground are key factors for proper TBM selection and design of machine technical specification. Adverse geological conditions encountered by boring machine during tunnelling, provides a great challenges and may trigger serious hazards especially in urban areas. This paper focused on investigation of geotechnical properties and relevant issues for mechanized tunnelling in the Tabriz metro line 3. Geological units of the tunnel alignment consist of alluvium deposits (fine to coarse grained with some cobble and boulder) in south and north parts and alternation of layers of soft rocks (marlstone, sandstone and mudstone) in the middle portion. Principal objects including detailed assessment of physical and mechanical parameters, soil grain size distribution, percentage of fine-grain content, equivalent quartz content, permeability and consistency have been investigated. Main geotechnical problems are occurrence of oversized rock particles, mixed face condition, soil abrasivity and clogging in the tunnel alignment and basically clear subsurface geological models to study these problems are constructed. Finally based on obtained data the proper TBM type and additional conditioning material for each section of the tunnel are suggested. In order to perform a successful mechanized tunneling, detailed surface and subsurface investigations on ground are key factors for proper TBM selection and design of machine technical specification. Adverse geological conditions encountered by boring machine during tunneling, provides a great challenges and may trigger serious hazards especially in urban areas. This paper focused on investigation of geotechnical properties and relevant issues for mechanized tunneling in the Tabriz metro line 3. Geological units of the tunnel alignment consist of alluvium deposits (fine to coarse grained with some cobble and boulder) in south and north parts and alternation of layers of soft rocks (marlstone, sandstone and mudstone) in the middle portion. Principal objects including detailed assessment of physical and mechanical parameters, soil grain size distribution, percentage of fine-grain content, equivalent quartz content, permeability and consistency have been investigated. Main geotechnical problems are occurrence of oversized rock particles, mixed face condition, soil abrasivity and clogging in the tunnel alignment and basically clear subsurface geological models to study these problems are constructed. Finally based on obtained data the proper TBM type and additional conditioning material for each section of the tunnel are suggested.