Shallow For High-speed Rail Tunnel Backfill Soil Deformation And Control Deformation Technology Research

With the advancement of the of national infrastructure construction, modern high-speed railway has achieved great development. During the Eleventh Five-Year period, especially in recent years, the mileage of high-speed railway has been several times of the past. As we all know, most of the western cities are built closing to the mountains and many of these cities are constructed by backfill soil. With the construction of many high-speed railways, many of the high-speed rail tunnels extend through the existing backfilled part. High-speed railway tunnels are beneath and extend through the city roads or buildings, so the study on the law of the deformation and the technology of controlling the deformation of the high-speed railway tunnels which extend through the backfilled part is particularly important.The engineering background of this paper is the Longdongbao airport tunnel in the first bid section of the project before the tie line station which connect newly built railway terminal Baiyun and Longlibei in Guiyang. We study the law of the deformation and the technology of controlling the deformation during the construction process by theoretical discussion and monitoring measurement technology at the site. The study and results of the study are showed as follows:Monitoring measurement are conducted to the backfilling shallow-buried section with V-class rock mass at the site. The data of the monitoring measurement at the site reveals the law of settlement deformation using the two-bench method and the arc heading method with big arch foot, which shows that the settlement deformation using the first method is larger than the second and the settlement deformation of the first method is2-3times larger than the second method during the construction process.The variation law of the displacement of the rock mass using the arc heading method with big arch foot. We find that the rate of deformation and the cumulative displacement of the rock mass in ultra-shallow backfill section are quite the same as the rules in the 《Standard of monitoring measurement in railway tunnel》. The deformation of the rock mass in ultra-shallow backfill section are integral, the settlement is relatively large both in the cave and on the ground.After analysing the reinforcing effect of vertical grouting of the surface and fracturing grouting inside the cave, the result is that vertical surface grouting can not effectively control surface subsidence and cave deformation inside the cave, but fracturing grouting could effectively control the cave settlement and rock mass convergence, and surface subsidence.Through on-site monitoring measurements under different construction methods (two-step method and the large arch foot curved heading method), the dates of surface settlement, the crown settlement, the rock mass convergence and arch foot settlement can be obtained in ultra-shallow segment backfill soil tunnel. These valuable information not only be used in this study but also provide some useful material and experience for other tunnel’s construction and design similar to this one.FLAC3D analysing software is used for ultra-shallow backfill soil tunnel under two different construction methods to proceed numerical simulation. The calculated results will be verified in contrast with field monitoring measurement.The above results show that the large arch foot curved heading method and the hole fracturing grouting inside the cave could control the deformation of the surface and inside the cave during construction of the Longdongbao Airport Tunnel. It also provides some experience for the future tunnel construction and design monitoring in similar ones.