盾构隧洞多层复合衬砌力学特性及其影响因素

Mechanical characteristics of multilayer composite lining of shield tunnel and their influencing factors

为了探索高内水压作用下盾构隧洞多层复合衬砌力学特征,文章以广州西江引水工程盾构隧洞为工程实例,分析多层复合衬砌承载及相互作用机制,建立复合衬砌盾构施工精细的计算模型,揭示复合衬砌力学特性及其影响因素,并以此为基础,评价复合衬砌防渗效果。研究表明:该实例多层复合衬砌可采用以压剪为主、局部抗压的相互作用模型;外管片在手孔处应力集中,局部出现了微裂缝,其他区域应力水平较低,复合衬砌能满足承载要求;外管片在内水压作用下接头张开,最大张开量小于接头极限变形值与张开量控制值,管片接头不会出现外水内渗;内衬自密实混凝土最大拉应变小于极限拉应变,也未形成贯通的塑性区,混凝土未出现裂缝,因而满足抗渗要求;内水压作用下内衬钢板产生的最大应力远小于屈服强度,这说明钢板仍然处于弹性承载阶段,其强度与刚度未被削弱;内衬钢板可有效地抑制内水压引起的衬砌外张,内衬混凝土应力随着钢板厚度的增加而减小;内衬轻质垫层的布置边界需避开外管片手孔、接头等部位,以减缓管片结构应力集中;不同内衬自密实混凝土厚度对衬砌应力影响较小,在隧洞净空允许的前提下宜取相对大的厚度。

In order to explore the mechanical characteristics of the multilayer composite lining of shield tunnel under high internal water pressure, the bearing and interaction mechanism of the multilayer composite lining were analyzed based on Guangzhou Xijiang Water Diversion Project. The refined model of the composite lining was established to reveal its deformation characteristics, and on this basis, the anti-seepage effect was evaluated. The results show that the interaction mode of the composite lining is mainly compression shear and local compression. The stress concentration in the outer segment appears in the hand hole and the micro-cracks appear locally. The stress level in other areas is low and the bearing capacity of composite lining meets the requirements. The outer segment joint opens under the internal water pressure, and the maximum opening is less than the control value and deformation limit of the joints, so the outer segment joint will not be infiltrated by water. The maximum tensile strain of the inner lining self-compacting concrete is less than the limit strain, the through plastic zone is not formed and the concrete has no crack, which meets the anti-seepage requirement. The maximum stress of inner lining steel is far less than the yield strength under internal water pressure, indicating that the steel is still in the elastic bearing stage, so its strength and rigidity are not weakened. Steel can effectively inhibit the lining deformation under internal water pressure and the concrete stress decreases with the increase of steel thickness. The gasket layout should avoid the hand hole and joint of the outer segment, so as to reduce the stress concentration. The thickness of self-compacting concrete has little influence on the lining stress, and the relatively large thickness should be selected when the tunnel clearance is allowed.