Title:
Circumferential Cracking of Concrete
Linings in Soft Ground Tunnels
Author(s):
Glenn E. Noble
Publication:
Concrete International
Volume:
6
Issue:
10
Appears on pages(s):
31-34
Keywords:
concretes; cracking (fracturing);
placing; temperature; tunnel linings.
inspection.
DOI:
Date:
10/1/1984
Abstract:
Twenty-seven miles (43.4 km) of concrete-lined sewers carrying sanitary sewage were inspected, and the findings and resulting analyses are presented, The inspection revealed excessive circumferential and longitudinal cracking. The tunnels were constructed during a 5 year period under 11 separate contracts, The age of the concrete lining at the time of inspection varied from five to nine years. The concrete lining varied from 24 to 12 in. (600 to 300 mm) in thickness for the 12.75 to 8.75 ft (3.8 to 2.6 m) internal diameter tunnels. Tunnel depths ranged from 100 to 50 ft (30 to 15 m) below ground surface, Tunnel excavation was performed by tunnel boring machines. Temporary support systems were installed behind the machines and the cast-in-place concrete lining followed. Two concrete mixes were furnished to provide a design strength of 3500 psi (24 MPa). Records were reviewed for documentation of varia-tions in construction methods, temporary earth support, concrete strengths, and methods of placement. The inspection findings and review of the construction records conclude that circumferential cracking is directly related to lining placement length and concrete temperature at time of placement.*