富水隧道施工期及运营期衬砌结构力学特性研究

以米亚罗3号隧道为依托工程,首先通过现场实测应力监测数据,对米亚罗3号隧道施工期支护结构应力的演变规律进行了分析研究;然后进一步借助数值分析软件,对不同初始水头高度下,米亚罗3号隧道运营期间围岩和衬砌结构的力学特征进行了研究。应力监测结果表明:隧道上台阶开挖后,拱顶和拱肩处的围岩-初支接触压力、钢拱架应力和外水压力迅速增大,约在30~40d后趋于稳定;下台阶开挖后,拱腰处的接触压力、钢拱架应力和外水压力快速增长,约在30~50d后趋于稳定;随着下台阶的开挖,拱肩处的围岩-初支接触压力再度缓慢增长,而钢拱架应力则明显下降;二衬施作后,其内力快速增长,并在20d后趋于稳定。数值模拟结果表明:当初始水头高度增加时,运营期间米亚罗3号隧道的洞周位移、二衬内力和外水压力均成一定比例的增加;隧道变形主要为竖直和水平方向的挤压变形,最大位移发生在拱底;相对于无地下水的情况,地下水的存在会影响衬砌弯矩分布,导致弯矩最大截面从拱顶转移至拱脚;衬砌所受外水压力在拱底处最小,其余部位分布较为均匀;随着初始水头的增大,拱腰和拱脚背后围岩的塑性区范围会明显增加。

Research on Mechanical Characteristics of Lining Structure for Enriched Water Tunnel During Construction and Operation Period

In this paper,based on the Miyaluo No.3 Tunnel,the evolution of the stress of supporting structure in the construction duration of Miyalo No.3 tunnel is analyzed and studied by the field measured stress data.Then,numerical analysis software is used to study the mechanical characteristics of surrounding rock and lining structure during the operation of Miyaluo No.3 Tunnel under different initial water head height.Stress monitoring results indicate that the contact pressure between surrounding rock and primary support,the stress of steel arch and the external water pressure at vault and spandrel increase rapidly after the excavation of upper bench,and tend to be stable after about 30-40 days.After the excavation of lower bench,the contact pressure,the stress of steel arch and the external water pressure at haunch increase rapidly,and tend to be stable after about 30-50 days.With the excavation of the lower bench,the contact pressure between surrounding rock and primary support increases again slowly,while the stress of the steel arch decreases obviously.The internal forces of secondary lining increase significantly after application and become stable after 20 days.The results of numerical simulation indicate that the peripheral displacement of tunnel,the internal forces of secondary lining and the external water pressure increase in proportion when the initial water head.Tunnel deformation is mainly compression deformation in the vertical and horizontal directions and the maximum displacement occurs at the arch bottom.Compared with the absence of groundwater,the presence of groundwater will affect the distribution of the bending moment of the lining,resulting in the cross-section of the maximum bending moment being transferred from the vault to the arch springing.The external water pressure is the smallest at the arch bottom and more evenly distributed on the other sections.With the increase of the initial water head,the extent of the plastic zone of the surrounding rock behind the haunch and arch springing will expand significantly.