Deformation rule of loess highway tunnel with two lanes

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 of 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.