A Study On Deformation Of Tunnel Excavated In Loess

In order to study the deformation of the Loess Tunnel, based on seven Loess tunnel belonging to the main route to State Road Qing'dao to Yin'chuan Shan'xi Habitat Wu'bu to Zi'zhou of the highway N12 ~ N16, planted a lot of the vault sank surrounding displacement measuring point with the geological conditions and engineering conditions in the loess tunnel, making a site monitoring on the deformation and the stability of the tunnel. Using finite element software (MIDAS-GTS) make a simulation analysis about the construction of the loess tunnel to study the law of deformation after excavation separately in the shallow and deep buried loess tunnel. The main conclusions were given out as:1. The measured data show that in the course of the Loess tunnel construction arch settlement is much larger than the clearance convergence, so in the construction of loess tunnel, how to control the arch settlement is a key issue. This paper proposed that the constrction must be adhering to the "fast-dug," "fast-support" and "rapid closure" of support for the concept, moreover, the lock angle bolt must be executed, and the inverted arch and secondary lining sidewall basis should keep up with the construction, And the results showed that the original standards and norms can not be fully applicable to the Loess tunnel construction.2. Using logarithmic function(u=A+Blnt) and the exponential function(u=Ae-B/t) make a regression analysis for the monitoring data applied, the results show that the loess deformation of the tunnel a few more in line with the logarithmic function .3. Drawing a conclusion by simulation analysis of finite element that the deformation of the shallow tunnel in the loess was about two to three times of the tunnel deep buried loess tunnel (measured data for the results of 3.5 times), and the deformation of with-bolt is about 1.5 times of without (measured data for the results of 1.2 times).4. Combined FEM analysis and site monitoring data to calculate the initial three days'displacement and the total displacement in tunnel, determine the key process in construction according to the displacement account of the separate process for the whole displacement, which provide for the construction of the A scientific basis and guidance to ensure that the construction of the safety and quality.The paper's achievements have sucsessfully supvised the construction of the Wu'bu to Zi'zhou of the highway, and made a good example for other engineerings.