Effect of Soil Conditioners on the Pressure and Rate-Dependent Shear Strength of Different Clays
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 138, Issue 9
Abstract
Tunneling using the earth pressure balance machines method in clayey soils requires the addition of conditioning chemicals to reduce the torque moment of the machine and to guarantee a safe and economical excavation process. Injection of foams and polymers at the cutter head of the tunnel boring machine with subsequent remolding in the pressure chamber transforms the excavated material into a deformable soil paste with preferably low strength and adhesion. The soil becomes more compressible and can develop viscous properties, such that the pressure and rate dependency of the shear strength of the mixtures are of major importance for the proper design and analysis of the tunneling processes. In this paper, the results of vane shear strength measurements on various conditioned clays and clay-sand mixtures at various shearing velocities and applied pressures are presented and analyzed. The results clearly show the effects of the chemicals used and also point out the differences in their efficiency depending on the clay mineralogy. This allows for an improved understanding of the working mechanisms of the chemicals.
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Acknowledgments
The presented work and apparatus is part of a research project between ETH Zurich and BASF Construction Chemicals Europe, Ltd., and MEYCO Global Underground Construction, Zurich, represented by Dr. A. Walliser and H. Egli. The project has been supported by the Swiss Confederations Innovation Promotion Agency (CTI; Grant No. 8554.2 EPRP-IW). Also, the support of the staff of the IGT workshop of ETH Zurich (A. Zweidler, E. Bleiker, H. Buschor, and A. Ehrbar), who designed and manufactured the vane shear test apparatus, is highly appreciated.
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Information & Authors
Information
Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 138 • Issue 9 • September 2012
Pages: 1138 - 1146
Copyright
© 2012 American Society of Civil Engineers.
History
Received: Mar 12, 2011
Accepted: Dec 6, 2011
Published online: Aug 15, 2012
Published in print: Sep 1, 2012
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