钢壳-混凝土组合沉管结构抗剪试验

深中通道隧道段采用钢壳-混凝土组合沉管结构(简称SSC组合结构)作为其主结构，隧道横断面抗剪性能成为该结构关键问题。为揭示该结构抗剪机理，基于深中通道沉管顶板局部构造及尺寸，以钢隔板间距、钢腹板间距为变化参数，设计3个缩尺比例为1∶2.5的SSC组合结构试件，开展抗剪试验及数值模拟分析。结果表明：与钢壳格室长高比2.20的试件相比，长高比1.10的试件抗剪极限承载力提高约21.3%;与格室宽高比1.88的试件相比，宽高比0.94的试件单宽抗剪承载力提高约43.4%,减小钢腹板间距、隔板间距能够提高SSC组合结构抗剪承载力；格室长高比2.20的试件破坏为混凝土腹部出现多条从支点到加载点的对角斜裂缝，并伴随加载点和支点处局部混凝土压溃；长高比为1.10的结构破坏为近跨中格室混凝土对角斜压破坏；SSC组合结构抗剪承载力主要由钢腹板和混凝土两部分分担，当长高比从2.20减小至1.10时，钢腹板分担的剪力几乎不变，但混凝土主压应变角度从约29.4°增大至约37.6°,混凝土分担剪力明显增加；钢腹板间距减小后，靠近腹板40%～50%截面高度范围内混凝土的主压应力增大，该范围以外的应力基本不变，表明...

Shear Experiment of Steel Shell-concrete Composite Structure in Immersed Tunnel

The steel shell-concrete composite structure (referred as SSC composite structure) is applied as the main structure in the immersed tunnel of Shenzhen-Zhongshan Link Project. The shear resistance in the transverse direction of tunnel is crucial to safety and rationality.To reveal shear mechanism of SSC composite structure, based on local details of the tunnel top slab, three SSC composite specimens with 1∶2.5 scale were tested and simulated under shear, considering different steel web spacing and steel diaphragm spacing. Results show that compared to the length height ratio of 2.20, the ultimate shear capacity of the specimen with the length height ratio of 1.10 is increased by 21.3%. For the width height ratio, compared to the ratio of 1.88, the ultimate shear capacity per width of the specimen with the width height ratio of 0.94 is increased by 43.4%.The specimen with length height ratio of 2.20 fails due to local compressive failure after diagonal cracks, while the specimen with length height ratio of 1.10 fails due to diagonal concrete compression crush in the midspan steel shell. The shear capacity of SSC composite structure is mainly shared by the steel web and concrete. When the length height ratio is decreased from 2.20 to 1.10, the shear force shared by the steel web is close to each other, while the shear force carried by the concrete increases significantly as the angle of concrete compressive principal strain increased from about 29.4° to 37.6 °. When the steel web spacing reduced, the principal compressive stress of concrete could be increased in the range of 0.4-0.5 times the section height near the steel web, and the stress out of the range remained the same, indicating that the composite effects between steel web and filled concrete could be exerted, resulting an improvement of concrete capability. Based on the mechanism analysis, the shear model of SSC composite structure in immersed tunnel is proposed, with the composite effects taken into consideration.