隧道高强钢管格栅与钢筋格栅承载特性室内模型试验

强化初期支护使之快速干预围岩应力状态是保障隧道施工及运营期安全稳定的有效途径之一。基于此,从“及时支护,强支护”理念内涵入手,对高强无缝钢管代替螺纹钢筋,以增强初期支护结构承载能力,从而实现变形控制的作用机理进行了研究。通过开展钢筋格栅和钢管格栅在单独受荷,与混凝土共同受荷条件下的室内加载试验,对2种支护结构的破坏形态、变形特征、极限承载力、全过程应力及裂缝发展规律等方面进行了系统分析。研究结果表明：2种支护结构的用钢量基本相同,但钢管格栅最大允许变形量和极限承载力分别为钢筋格栅的1.6倍和1.8倍,验证了高强度无缝钢管可以有效改善格栅结构的承载性能;钢筋格栅表现出折线形压弯破坏,而钢管格栅表现为平滑曲线形破坏,且卸载后回弹变形量更大;钢管格栅混凝土试件具有与钢筋格栅混凝土试件相近的抗弯刚度,极限承载力较钢筋格栅混凝土试件提高了22.5 %;钢筋格栅自身承载力有限,与混凝土形成组合结构后方能具备较高的承载能力;钢管格栅具有高强度高韧性的特点,结构受力合理,可以及时、有效地对围岩提供径向支护力,适合于软弱破碎、早期变形速度快的围岩条件。

Model Tests on Bearing Characteristics of High-strength Steel Tube Grid and Lattice Girder in Tunnel

Strengthening the primary support to quickly intervene the stress state of surrounding rock was one of the effective ways to ensure the safety and stability of the tunnel during construction and operation periods. Starting from the connotation of "timely support and strong support", the mechanism of high-strength seamless steel tubes instead of threaded reinforcement to enhance the bearing capacity of primary support structure to realize deformation control was studied. This paper carried out laboratory loading tests of steel tube grids and lattice girders under the conditions of single load and common load with concrete. The failure forms, deformation characteristics, ultimate bearing capacity, complete stress process, and crack development laws of the above structures were systematically analyzed. The results showed that steel consumption of the two supporting structures was basically the same, but the maximum allowable deformation and ultimate bearing capacity of the steel tube grid were 1.6 times and 1.8 times than that of the lattice girder, respectively, which verified that the high-strength steel tubes can effectively improve the bearing performance of this structure. The lattice girder exhibited broken-line bending failure, but the steel tube grid represented smooth curve failure, and the rebound deformation was greater after unloading. The flexural rigidity of steel tube grid concrete member was essentially the same as that the lattice girder member, and the ultimate bearing capacity was 22.5 % higher than that of lattice girder concrete member. The bearing capacity of lattice girder itself was limited, and it had a higher bearing capacity after forming a composite structure with concrete. The steel tube grid had the characteristics of high strength and high toughness, and the structural force was reasonable. Additionally, it could provide radial support to the surrounding rock in a timely and effective manner, and it was more suitable for weak and broken surrounding rock conditions with rapid early deformation.