隧道与斜井交叉段用钢纤维砼支护受力研究

空间交叉结构受力复杂性及其支护结构适应性是近年来长大公路隧道亟待解决的关键技术问题。采用喷射钢纤维混土做永久衬砌以替代复合式衬砌,可满足交叉结构承受弯曲应力作用下强度要求,同时从根本上解决了支护结构的施工性问题。从钢纤维混凝土(SFRC)抗拉韧性性能研究入手,通过四点弯曲试验,获得了钢纤维混凝土的裂缝宽度w与裂缝高度关系以及钢纤维混凝土开裂后拉应力随裂缝宽度增加而降低的拉伸软化曲线。在有限元计算中,引入应变软化模量以及剪切滞后因子两个特征参数,对云山隧道与斜井(3#)钢纤维混凝土交叉支护结构进行三维有限元数值模拟,探明了钢纤维混凝土支护隧道交叉连接段局部范围内位移变形、裂缝分布、接触应力等演化的施工力学行为,研究结果可为采用钢纤维混凝土做永久结构设计、施工以及合理支护参数选择提供有益参考。

Study on Mechanical Characteristics of SFRC Lining at Intersection of Inclined Well and Tunnel

Mechanical characteristics of intersection structure of long highway tunnel and adaptability of its supporting structure are the key technical issues at present. Spraying steel fiber reinforced concrete taken as the permanent lining instead of composite lining at intersection structure can satisfy the strength requirement of supporting under the action of bending stress, and the problem of retaining structure construction can be fundamentally solved in the intersection construction between two tunnels. Based on analysis of SFRC(steel fiber reinforced concrete) tensile toughness, the relationship between the crack width (w) and crack height is obtained by four-point bending test. Furthermore, the tensile softening curve is got in this paper which reflects that the stress of concrete decreases with the increase of crack width after SFRC cracking. Through introducing the stress-strain softening curve and shear softening curve, the mechanical behavior of intersection of inclined well and long highway tunnel is studied by using 3D finite element numerical simulation. The research provides a useful reference to construction and the reasonable supporting parameters in the design taking SFRC as permanent structure of the tunnel.