Parametric studies on the interaction between existing and new bored tunnels

In Singapore, the increase of underground tunnel infrastructure implies a need to make rational and efficient use of underground space. Therefore, new tunnels have to be constructed more often in close proximity to the existing tunnels to accommodate transportation system and utility networks such as water supply and sewerage system. Prediction of stresses induced in existing tunnels due to the excavation of new adjacent tunnels is therefore crucial to ensure that excessive stresses are not developed in the lining of the existing tunnels. A numerical study has been performed to investigate the effect of a new bored tunnel on the stresses induced in the lining of an existing adjacent tunnel. The two-dimensional finite element method program PLAXIS was adopted in the investigation. In the analysis, typical lining and soil parameters of the North-East line MRT Tunnel in Singapore were adopted. Results of the study demonstrate that the position of the new bored tunnel relative to the existing tunnel, the distance between the new and existing tunnels, the volume loss, the depth of burial and the lining thickness have significant effect on the bending moment induced in the existing tunnel after interaction with the new adjacent tunnel. When the new tunnel is excavated above the existing tunnel, there is a decrease in the maximum bending moment induced in the lining of the existing tunnel. For cases of small percentage of volume loss (less than about 0.5%), the excavation of the new tunnel below the existing tunnel leads to an increase in the bending moment in the lining of the existing tunnel. For cases of volume loss greater than 0.5%, the excavation of the new tunnel beside the existing tunnel may lead to significant increase in the bending moment of the existing tunnel. Besides, the decrease of distance between tunnels may lead to substantial increase in the bending moment induced in the existing tunnel for cases of volume loss greater than 0.5%. The critical distance between the two tunnels below which the bending moment increases substantially is about five times of tunnel radius (centre-to-centre). As the volume loss increases, the bending moment induced in the lining of the existing tunnel increases. The lining flexibility of both the new and existing tunnels plays an important role in the value of the induced bending moment after interaction. The increase in maximum bending moment after interaction is larger for stiffer lining. It has been shown that the interaction mechanisms between two tunnels in close proximity are highly complex. The results obtained from this study are believed to be useful for interpretation of field measurements and design considerations. (A). "Reprinted with permission from Elsevier". For the covering abstract see ITRD E124500.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/08867798
• Authors:
  • HEFNY, A M
  • CHUA, H C
  • ZHAO, J
• Publication Date: 2004-7

Language

• English

Media Info

• Pagination: p471
• Serial:
  • TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY. UNDERGROUND SPACE FOR SUSTAINABLE URBAN DEVELOPMENT. PROCEEDINGS OF THE 30TH ITA-AITES WORLD TUNNEL CONGRESS SINGAPORE, 22 - 27 MAY 2004
  • Volume: 19
  • Issue Number: 4-5
  • Publisher: Elsevier
  • ISSN: 0886-7798

Subject/Index Terms

• TRT Terms: Conferences; Stresses; Transportation; Tunnels
• Geographic Terms: Singapore
• ITRD Terms: 8525: Conference; 8101: Singapore; 5575: Stress (in material); 1155: Transport; 3374: Tunnel
• Subject Areas: Bridges and other structures; Construction; Transportation (General); I54: Construction of Tunnels;

Filing Info

• Accession Number: 01011628
• Record Type: Publication
• Source Agency: Transport Research Laboratory
• Files: ITRD
• Created Date: Dec 19 2005 3:22PM