Damage mechanism of shield tunnel under unloading based on elastoplastic damage model of concrete

被引：0
|
作者：
Liu J. [1 ]
Shi C. [1 ]
Lei M. [1 ,2 ]
Peng L. [1 ]
Wang Z. [1 ]
机构：
[1] School of Civil Engineering, Central South University, Changsha
[2] MOE Key Laboratory of Engineering Structure of Heavy Haul Railway, Central South University, Changsha
来源：
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | 2021年 / 52卷 / 03期
基金：
国家重点研发计划; 中国国家自然科学基金;
关键词：
3D discontinuous contact model; Elastoplastic damage model of concrete; Multiscale mixed modelling technology; Shield tunnel; Unloading stress;
D O I：
10.11817/j.issn.1672-7207.2021.03.010
中图分类号：
学科分类号：
摘要：
Engineering activities in the vicinity of dense metro traffic network caused large longitudinal differential deformation of the underlying shield tunnel, which adversely affected the service performance and traffic safety of the metro system. Previous relevant studies were mostly carried out within the framework of elastic or elastoplastic theory, despite the influence of structural damage caused by longitudinal deformation of shield tunnel. The nonlinear damage characteristics of concrete material were considered, and a novel positive/negative decomposition of stress tensor in energy norm was introduced to consider the asymmetric tensile/compressive material behavior of concrete. Secondly, a bi-scalar damage constitutive model of concrete was further developed. Finally, to investigate the damage and degradation mechanisms of shield tunnel under unloading, 3D discontinuous contact model in conjunction with multiscale mixed modelling technology was employed to develop tunnel-soil numerical model. The results show that when shield tunnel suffers unloading stress, localized tension damage dominates while compression damage is minor. The severest tension damage is observed at the inner sides of tunnel crown and bottom, outer sides of tunnel waist, and bolt connections. Tunnel heave is induced by unloading process, ellipticity of tunnel cross section varies along the longitudinal direction, and the maximum convergence deformation is observed at the segmental ring near the inflection point. The unloading-induced maximum additional shear force appears near the inflection point, while the peak bending moment is observed at the model center. The damage and degradation of concrete materials will reduce the tunnel bearing capacity, longitudinal and circumferential stiffness, whilst the elastic-based model will overestimate the integral structural stiffness. According to the investigated cases herein, the segmental rebar is hard to yield, while the longitudinal coupling bolts on the tunnel upper half are easier to yield. It should be noted that the segmental rings near the inflection point are most seriously damaged, and bear large shear forces and bending moments. © 2021, Central South University Press. All right reserved.
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页码：758 / 769
页数：11
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