Location

Chicago, Illinois

Session Start Date

4-29-2013

Session End Date

5-4-2013

Abstract

The highly inhomogeneous nature of the river deposits in central Esfahan induced unforeseen problems for tunneling of 2×5 km long of middle section of the Esfahan Subway Project. A noticeable phenomenon in these course grained fluvial (river) deposits is the locally cementation of the soil particles by a calcium carbonate binder and formation of some semi-hard to hard conglomerate lenses. This unique phenomenon is named locally as “Sovord” rock and could be seen just in semi-aired regions as central Iran. Two 6.89 m diameter EPBTBM machines were employed to excavate shallow tunnels in the vicinity of fragile structures of the old city. The main unwanted impacts of this highly cohesive pseudo-rock were noticed as high vibration, temperature raising, tunnel face instability, low rate of machine’s advance, early tools damage and finally great cutter-head damage after the first major collision with this unpredicted phenomenon. We analyzed geotechnical characteristics of this material and the corresponding effects on face supporting pressure, foaming agents, soil conditioning process and operational policy. Lowering the cylinder thrust force, ≤9000KN, improving the cutting wheel rotation speed, ≥2.5RPM, using some anti-abrasive foaming agents, ABR2 lubricants, and periodic tools inspection schedule was considered as solution for the indicated problem.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Seventh Conference

Publisher

Missouri University of Science and Technology

Publication Date

4-29-2013

Document Version

Final Version

Rights

© 2013 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Apr 29th, 12:00 AM May 4th, 12:00 AM

Promotion of Tunneling Performance in Locally Semi-Hard to Hard Conglomerate Lenses, Case of Esfahan Historical City Subway Project

Chicago, Illinois

The highly inhomogeneous nature of the river deposits in central Esfahan induced unforeseen problems for tunneling of 2×5 km long of middle section of the Esfahan Subway Project. A noticeable phenomenon in these course grained fluvial (river) deposits is the locally cementation of the soil particles by a calcium carbonate binder and formation of some semi-hard to hard conglomerate lenses. This unique phenomenon is named locally as “Sovord” rock and could be seen just in semi-aired regions as central Iran. Two 6.89 m diameter EPBTBM machines were employed to excavate shallow tunnels in the vicinity of fragile structures of the old city. The main unwanted impacts of this highly cohesive pseudo-rock were noticed as high vibration, temperature raising, tunnel face instability, low rate of machine’s advance, early tools damage and finally great cutter-head damage after the first major collision with this unpredicted phenomenon. We analyzed geotechnical characteristics of this material and the corresponding effects on face supporting pressure, foaming agents, soil conditioning process and operational policy. Lowering the cylinder thrust force, ≤9000KN, improving the cutting wheel rotation speed, ≥2.5RPM, using some anti-abrasive foaming agents, ABR2 lubricants, and periodic tools inspection schedule was considered as solution for the indicated problem.