两车道公路黄土隧道变形规律

Deformation rule of loess highway tunnel with two lanes

依托国道主干线GZ35青岛至银川高速公路陕西境内吴堡至子洲沿线上7座单洞两车道分离式黄土隧道,现场测试了隧道施工变形,并对测试结果进行了回归分析。分析结果表明:台阶法施工过程中黄土隧道拱部沉降远大于净空收敛;黄土隧道变形大致经历了急剧变形阶段(开挖初期)、持续增长阶段与缓慢增长阶段;黄土隧道的变形规律符合对数函数规律,由于对数函数具有发散性,故无法由此预估围岩的最终位移,围岩变形将长期处于缓慢增长状态;按照规范规定的最终速率值预估二次衬砌施作时机不符合工程实际要求,不能保证隧道围岩和支护结构的稳定和施工安全,因此,在黄土隧道的施工中,需要以控制拱部的沉降来控制隧道的变形。施工中必须秉承"快挖、快支、快封闭"的原则,采取加强初期支护,增设锁脚锚杆,仰拱和二次衬砌边墙基础紧跟,二次衬砌适时施作的措施,避免拱部围岩发生过大的沉降,确保隧道结构稳定。

Relying on seven single-tunnel double-lane loess tunnels at Wubu to Zizhou section in Shaanxi Province on national main trunk line GZ35 from Qingdao to Yinchuan, the constructing deformations were messured by in-situ test method, and the regression analysis of test results was carried out. Analysis result shows that in the constructing process by using bench method, the arch settlements are far bigger than the clearance convergences. The tunnel deformation of surrounding rock experiences three stages： rapid deformation stage at the initial stage of excavation, sustainable growth stage and slow increasing stage. The deformation rule of loess tunnel accords with logarithmic distribution, but the logarithmic function is divergent, so the final displacement is not predicted. The deformation of surrounding rock is slowly increasing for a long time. It is not in accordance with the actual requirements and can not guarantee the stabilities of tunnel surrounding rock and supporting structure, and construction safety when the constructing time of secondary lining is estimated by using norms. So the deformation of tunnel should be controlled by using arch settlement in the constructing process of tunnel. The constructing principle o{ rapid excavating, rapid supporting and rapid closing is put forward for loess tunnel. Strengthening initial supporting, adding crus-locking anchors, quick constructing side walls and timely constructing secondary lining are carried out to avoid large settlement of arch surrounding rock and to ensure the stability of tunnel structure. 6 tabs, 17 figs, 12 refs.