钢板-混凝土组合结构加固盾构隧道衬砌结构极限承载力足尺试验

提出钢板-混凝土组合结构加固盾构隧道衬砌结构的加固方法,该方法采用钢板作为加固材料,钢板与原衬砌结构的界面黏结采用栓钉、植筋、化学锚栓和钢纤维混凝土组合而成的物理界面黏结。其中,焊接于钢板表面的栓钉作为钢板与钢纤维混凝土之间界面的抗剪连接件,植入原混凝土衬砌内表面的植筋作为原混凝土与钢纤维混凝土之间界面的抗剪连接件,化学锚栓提供钢板与原混凝土之间的径向抗剥离力,而采用钢纤维混凝土作为钢板与原混凝土衬砌之间的填充材料,其具有良好的抗裂性能与耐久性。这种界面黏结形式相比传统盾构隧道加固方法中由环氧树脂形成的化学界面黏结,提高了界面的强度、延性以及耐火性,改变了传统盾构隧道加固方法中,结构破坏源自局部界面黏结脆性破坏的破坏模式。以通缝拼装盾构隧道为加固对象,对加固试件进行模拟上部堆载作用下考虑二次受力的整环足尺静力加载试验,分析结构整体的受力过程、破坏模式和极限承载力等,探究钢板-混凝土组合结构加固法对于提高结构受力性能的作用,并将试验结果与内张钢圈加固法进行比较。研究表明:采用钢板-混凝土组合结构加固法加固盾构隧道,保证了界面黏结的有效性,极限承载力状态下,界面黏结良好,使得加固材料与原混凝土衬砌结构能够共同工作,提高了各类材料(钢板、螺栓等)的利用率,结构整体破坏模式具有良好的弹塑性;相比于内张钢圈加固法,钢板-混凝土组合结构加固法的钢材用量减少了29.4%,而结构极限承载力提高了31.1%,结构延性增加501%。

Experiment of Deformed Shield Tunnels Strengthened by Steel Plate-concrete Composite Structure

A new strengthening technique for a deformed shield tunnel, called the steel plate-concrete composite structure (SPCCS) strengthening technique, was proposed. In this technique, the steel plate is employed as the strengthening material, and a combination of struts, planting reinforcing bars, chemical anchors, and steel fiber-reinforced concrete are used to create the bond between the steel plate and tunnel lining. The struts welded to the surface of the steel plate are employed as shear connectors of the interface between the steel plate and steel fiber-reinforced concrete; the planting reinforcing bars are employed as the shear connectors of the interface between the tunnel lining and steel fiber-reinforced concrete; and the chemical anchors are used to provide the radial force resistance between the tunnel lining and steel plate. Fiber-reinforced concrete has high durability and high crack resistance properties. It replaces the bond established by epoxy in traditional strengthening techniques, which increases the strength, ductility, and fire resistance of the bond, and changes the failure mode of traditional strengthening techniques for shield tunnels such that structural failure is initiated from bond failure. A full-scale static loading test was conducted under the overburden secondary loading scheme. The whole process of structural behaviors, failure mode, and ultimate bearing capacity were investigated. A comparison between the SPCCS strengthening technique and epoxy-bonded steel plate strengthening technique was conducted. The results show that for the shield tunnel strengthened by the SPCCS strengthening technique, the effectiveness of the bond increased, which made the strengthening material work more efficiently with the tunnel lining and made full use of every material (steel plate, bolt, etc.). The failure mode of the strengthened structure has high elastoplasticity. Compared with traditional steel plate strengthening, the SPCCS strengthening technique decreases the quantity of steel by 29.4%, but increases the ultimate bearing capacity and ductility by 31.1% and 501%, respectively.