ADECO full-face tunnel excavation of two 260 m super(2) tubes in clays with sub-horizontal jet-grouting under minimal urban cover
With a cover of 5-30 m, a 260 m super(2) cross-sectional area, and a 4-m wide pillar, the Cassia twin road tunnels underpass Cassia road (main road to/from Rome), the remnants of a 2000 year-old Roman villa, and two existing tunnels. Stiff silty clay dominates the alignment. According to the Analysi...
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Published in | Tunnelling and underground space technology Vol. 26; no. 2; pp. 253 - 266 |
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Main Author | |
Format | Journal Article |
Language | English |
Published |
01.03.2011
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Subjects | |
Online Access | Get full text |
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Summary: | With a cover of 5-30 m, a 260 m super(2) cross-sectional area, and a 4-m wide pillar, the Cassia twin road tunnels underpass Cassia road (main road to/from Rome), the remnants of a 2000 year-old Roman villa, and two existing tunnels. Stiff silty clay dominates the alignment. According to the Analysis of Controlled DEformations (ADECO) principles, each tube was excavated full face to 260 m super(2). Compared to Sequential Excavation Method (SEM), this highly simplifies construction, leads to construction industrialization, and allows for full control of the ground ahead of the face, which is used as a stabilization measure. In order to pre-confine the tunnel core, Trevi roto-injection technique was used to create an umbrella of overlapping sub-horizontal reinforced jet-grouting columns ahead of the face, while avoiding up heave of the ground or emptying of the columns. Stiff preliminary lining sitting on sub-horizontal jet-grouting columns, final invert close to the tunnel face, and final lining no more than 50 m behind the face ensured that the pre-confinement ahead of the tunnel face became effective confinement around the cavity. The tunnels were finished on schedule and within budget with a mere 1 cm of settlement. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 content type line 23 ObjectType-Feature-1 |
ISSN: | 0886-7798 |
DOI: | 10.1016/j.tust.2010.09.006 |