隧道双层预支护力学分析模型

Mechanical analysis model for double layered pre-support in tunnel

为了研究隧道施工双层预支护体系的协同作用机制和作用效果,考虑管棚、旋喷桩、注浆等预加固方式的协同作用,将双层预支护结构等效为梁单元,将预支护结构之间的土体视作弹簧单元,支撑预支护两端的连续墙采用弹性支座模拟,采用不同的梁单元刚度模拟隧道施工过程中结构抗弯刚度的变化,建立隧道施工双层预支护体系的力学分析模型。推导分析模型的耦合挠曲微分方程组,结合边界条件,得到挠曲理论解。以广佛(广州—佛山)环线城际铁路东平一号隧道为背景,选取下层预支护结构拱顶纵向中间位置的沉降进行对比分析。研究结果表明:中间位置沉降的理论计算值、有限元计算值和实测值分别为4.0,3.7和3.9 mm,误差在可接受范围内,验证了模型的可靠性;中间土体弹簧与水平旋喷桩直径分别对体系的协同作用、挠曲变形有较大影响。

In order to research the synergistic mechanism and effect of the double layered pre-support system during tunnel construction,considering the synergistic effect of pipe roof,swirling pile and grouting,the double layered pre-support structures were equivalent to beam elements,the soil which was between the pre-supports was regarded as spring element,the underground diaphragm wall which supported the pre-support structures was simulated with elastic support,various bending stiffness values were used to simulate the change of structural flexural rigidity during construction,and the mechanical analysis model of double layered pre-support system for tunnel construction was established.Coupled differential equations of the double layered pre-support analysis model were derived,and theoretical solutions were obtained combined with boundary conditions.Under the background of Dongping No.1 tunnel in Guangdong-Foshan Ring Intercity Railway,the point which was located at the longitudinal middle position of the crown of the lower pre-support structure was selected for settlement comparative analysis.The results show that the settlement of theoretical computing,finite element calculation and measurement of this point are 4.0,3.7 and 3.9 mm,respectively.The error is acceptable,and reliability of the model is verified.The middle soil spring stiffness and the diameter of the horizontal jet grouting pile have great influence on the synergistic effect and the flexural deformation of the system,respectively.