考虑不均匀沉降影响的多厢互联预应力渡槽安全评估研究

多厢互联式渡槽是针对南水北调输水量大而专门提出的一种新型渡槽结构型式,与传统单厢渡槽相比,这种新型渡槽纵向与横向尺寸相差不大,并采用三向预应力设计,导致其横向刚度与纵向刚度相差不大,承载以后的受力表现更像板而不是梁,这种结构挠度变形很小,但对不均匀沉降变形异常敏感。为此,以某三厢互联预应力渡槽为例,通过对现有沉降变形监测资料进行分析,提出了两种不同类型不均匀沉降变形模式,即"一头倒"和"扭麻花"沉降变形模式,并指出实际不均匀沉降是上述两种的复合模式。同时,当不均匀沉降发生时,将会改变槽身受力状态,对渡槽安全运行产生不利影响;随着不均匀沉降变形增大,槽身内壁及外壁应力状态逐渐恶化,内壁受拉区范围逐渐增大,最大拉应力值也逐渐增大;该不均匀沉降变形达到当前状态的1.5倍时,槽身内壁环向正应力将超过1.70 MPa,内壁存在很大的开裂风险。

Uneven settlement effect-considered study on safety assessment of multi-trough interconnected and prestressed aqueduct

The multi-trough interconnected aqueduct is a new type of aqueduct structure，which is specially proposed for the large water conveyance amount of the South-to-North Water Transfer Project． Compared with the traditional trough aqueduct，no large difference is there between both the longitudinal and transverse dimensions of this new type aqueduct，for which a 3D prestressing design is adopted; which makes no large difference is there between the traverse stiffness and longitudinal stiffness of it and leads its stress performance to be more like a plate than a beam after loading． The deflection of this type of structure is quite small，but is very sensitive to uneven settlement deformation． Therefore，a tri-trough interconnected and prestressed aqueduct is taken as the study case，and then two kinds of the uneven settlement deformation modes，i． e． one-end tilting and twisting，are put forward through the analysis made on its existing settlement deformation monitoring data，while it is indicated that the actual uneven settlement is just a compound mode of both the modes mentioned above． When the uneven settlement deformation occurs，the stress state of the aqueduct body is to be changed，which has an adverse effect on the safe operation of the aqueduct． Along with the increase of the uneven settlement deformation，the stress states of both the inner wall and the outer wall are to be gradually deteriorated with the gradual increase of the tensile zone of the inner wall and the gradual increase of the maximum tensile stress． When the uneven settlement deformation reaches 1. 5 times that of the current state，the circumferential normal stress of the inner wall of the aqueduct body is to exceed 1. 70 MPa，thus a great cracking risk is there for the inner wall． The study result can provide the relevant engineering references for the similar project concerned．