Restrained shrinkage and early age crack in tunnel construction

Title: Restrained shrinkage and early age crack in tunnel construction
Author(s): Y. Cai, Y. Yuan
Paper category : conference
Book title: International Conference on Advances in Concrete and Structures
Editor(s): Ying-shu Yuan, Surendra P. Shah and Heng-lin Lü
Print-ISBN: 2-912143-41-1
e-ISBN: 2351580176
Publisher: RILEM Publications SARL
Publication year: 2003
Pages: 286 - 291
Total Pages: 6
Nb references: 5
Language: English

Abstract: 
It is very popular that lining concrete cracks during construction period in Japan, which is a potential threat to its service life. Restrained shrinkage initialed by different reasons such as temperature, autogenous or drying shrinkage, is the main cause for cracking. However, time effect is often neglected because of its complexity. A mechanical model is proposed in this paper to calculate the initial stress in circular lining concrete for different kind of shrinkage at early age. Time-dependent effect is considered in the model and the concept of restrained degree of circular tunnel structure is defined. Analysis shows that restrained degree of rock substrate is determined by the deformation modulus of rock mass and the geometry of tunnel lining. The higher deformation modulus will induce large initial stress in concrete lining. With the time passing by, restrained degree decreases while initial stress increases. Based on the classification of rock mass, the restrained degree of circular tunnel is suggested. When internal radial of tunnel equals 4.5m and lining thickness is 0.2m. Decreasing restrained degree of tunnel is insignificant when deformation modulus of rock mass is larger than 5.0GPa.

Online publication: 2003-08-10
Publication type : full_text
Public price (Euros): 0.00