Study on dry shrinkage crack of invert-filling in the shield tunnel at mesoscale based on virtual element-finite element coupling method
Jin Hao1Zhou Yuliang2
1. Southeast University, Nanjing 211189, China;
2. The Key Laboratory of Road and Traffic Engineering of Ministry of Education, Tongji University, Shanghai 201804, China
Abstract：To explain dry shrinkage cracking phenomenon of invert-filling in the shield tunnel, the mechanism of crack formation caused by dry shrinkage of new concrete after pouring was studied. The stiffness matrix format of aggregate with the shape of arbitrary polygon was deduced based on virtual element, and the coupling calculation of finite element and virtual element was realized by UEL subroutine. The numerical test results of beams in pure bending show that the coupling method is more efficient than the finite element method and has better stability. On that basis, the dry shrinkage numerical model of new and old concrete was consequently established at mesoscale, and the model parameters were verified by the disk drying shrinkage model. The stress distribution of aggregate and mortar, the relationship between internal humidity and crack development, and the stress development of new and old concrete surface and their interface were studied. The results show that: ①during the shrinkage process, the aggregate is mainly subjected to compressive stress, and the mortar along the tangent direction of the aggregate boundary is subjected to the aggregate constraint so that shrinkage cracks are easily formed. A large number of micro-cracks appear on the surface of the new concrete first, followed by the debonding at both ends of the interface. ②Restricted by the aggregate below the surface, the surface tensile stress of new concrete presents a “hump” distribution. After cracking, the surface is divided into several contraction zones, the boundary and the internal of the contraction zone are subjected to tensile stress and compress stress, respectively;③The tensile and shear stresses of the interface begin to increase from both sides and move inward gradually with the increase of the interface debonding. The local compressive stress and shear stress may increase due to aggregate constraint in the bonding region inside the interface.
金浩 周瑜亮. 基于虚拟元-有限元耦合的隧道内道床干缩裂缝细观研究[J]. 土木工程学报, 2022, 55(4): 109-119.
Jin Hao Zhou Yuliang. Study on dry shrinkage crack of invert-filling in the shield tunnel at mesoscale based on virtual element-finite element coupling method. 土木工程学报, 2022, 55(4): 109-119.
