Stability of long unsupported twin circular tunnels in soils

Sahoo, Jagdish Prasad and Kumar, Jyant (2013) Stability of long unsupported twin circular tunnels in soils. In: TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY, 38 . pp. 326-335.

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Abstract

The stability of two long unsupported circular parallel tunnels aligned horizontally in fully cohesive and cohesive-frictional soils has been determined. An upper bound limit analysis in combination with finite elements and linear programming is employed to perform the analysis. For different clear spacing (S) between the tunnels, the stability of tunnels is expressed in terms of a non-dimensional stability number (gamma H-max/c); where H is tunnel cover, c refers to soil cohesion, and gamma(max) is maximum unit weight of soil mass which the tunnels can bear without any collapse. The variation of the stability number with tunnels' spacing has been established for different combinations of H/D, m and phi; where D refers to diameter of each tunnel, phi is the internal friction angle of soil and m accounts for the rate at which the cohesion increases linearly with depth. The stability number reduces continuously with a decrease in the spacing between the tunnels. The optimum spacing (S-opt) between the two tunnels required to eliminate the interference effect increases with (i) an increase in H/D and (ii) a decrease in the values of both m and phi. The value of S-opt lies approximately in a range of 1.5D-3.5D with H/D = 1 and 7D-12D with H/D = 7. The results from the analysis compare reasonably well with the different solutions reported in literature. (C) 2013 Elsevier Ltd. All rights reserved.

Item Type:	Journal Article
Publication:	TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY
Publisher:	PERGAMON-ELSEVIER SCIENCE LTD
Additional Information:	copyright for this article belongs to PERGAMON-ELSEVIER SCIENCE LTD,ENGLAND
Keywords:	Finite elements; Limit analysis; Optimization; Stability; Tunnels; Upper bound solution
Department/Centre:	Division of Mechanical Sciences > Civil Engineering
Date Deposited:	08 Jan 2014 06:05
Last Modified:	08 Jan 2014 06:05
URI:	http://eprints.iisc.ac.in/id/eprint/48157

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