地基沉降引发输水盾构隧道复合结构受弯分析

Foundation settlement-induced bending analysis of composite structures in water-conveying shield tunnels

结合混凝土、螺栓和钢管的弹塑性变形特性,基于纵向等效连续模型和平截面假定,建立衬砌管片、输水钢管及在衬砌管片与输水钢管之间填充混凝土的受弯分析模型.求解该模型,得到地基沉降作用下盾构隧道纵向接缝张开量、最大混凝土压应变及最大钢管拉应变等关键参数.将所建模型应用于杭州某输水盾构隧道工程,结果表明:地基沉降引起隧道受弯,隧道结构将产生7类临界状态,且先后顺序为螺栓达到屈服应力、环缝张开2 mm (螺栓和管片混凝土被侵蚀)、钢管达到屈服应力、环缝张开6 mm(钢管和填充混凝土被侵蚀)、管片混凝土开始受压屈服、填充混凝土开始受压屈服、螺栓达到破坏应力.当钢管紧贴衬砌管壁时,隧道结构处于最不利工况,容易导致钢管腐蚀和隧道脆性破坏.

Combining the elastic-plastic deformation characteristics of concrete,bolts,and steel tube,a model for bending analysis of tunnel lining segments,water-conveying steel tube,and concrete filled in between tunnel lining segments and water-conveying steel tube was established based on the longitudinal equivalent continuous model and the plane cross-section assumption.The key parameters for the shield tunnel under the influence of ground settlement were obtained by solving the model.These parameters include the longitudinal joint opening of shield tunnels,the maximum concrete compressive strain,and the maximum steel tube tensile strain.The established model was applied to a water-conveying shield tunnel project in Hangzhou.The results indicate that ground settlement causes the tunnel to bend,leading to seven critical states in the tunnel structure.The sequence of these critical states is as follows:bolts reach yield stress,2 mm opening of circumferential joints(bolts and segment concrete are eroded),steel tube reaches yield stress,6 mm opening of circumferential joints(filled concrete-steel tube is eroded),segment concrete begins to experience compressive yield,filled concrete begins to experience compressive yield,and bolts reach failure stress.When the steel tube is in close contact with the lining wall,the tunnel structure is in the most unfavorable condition,which can lead to steel tube corrosion and tunnel brittle failure.