Tunnel Construction Monitoring And Back Analysis Of Rock Parameters From Measured Displacements

With the wide use of New Austrian Tunneling Method (NATM) in tunnel engineering in our country, the site monitoring and measurement is as one of the three pillars of NATM and gets more and more attention. Tunnel monitoring can reflect the dynamic changes of the system of rock and supporting, and the processing of the site data measuring timely can provide the basis for the parameters adjustment of the initial supporting and lining. It can play an important role as"eyes"during the tunnel construction. Also, the monitoring measurement can play the role of information feedback, and provides basis for the adjusting rock mass. Usually, in order to obtain the mechanical parameters of rock, laboratory and in-situ tests are taken. Because of the heterogeneity and non-continuity of rock mass, it is difficult to reflect the parameters of the rock mass properties, and applied in mechanical calculation. On the other side, using the displacement back analysis method can overcome these shortcomings, and the operation is simple.Based on project of Pingyikou Tunnel in Yiba Highway, the tunnel monitoring measurement is introduced and the monitor data analysis is carried on the regression method. The back analysis of the displacements is used to determine the mechanical parameters of the rock mass. The main contents of the thesis are as follows.Firstly, the background of Pingyikou Tunnel is introduced, including the geographical environment, the engineering geology, the hydro-geological, the design of the tunnel entrance and the design of tunnel lining.Secondly, the principle and objective of the tunnel monitoring measurement is introduced.Thirdly, the obligatory test and the chosen test items of Pingyikou Tunnel are determined. The actual monitoring results are studied, and the monitor data analysis is carried on the regression method. The final deformation of the rock and the reasonable time of the lining construction are predicted using the regression analysis.Finally, the back analysis method is summarized and classified, and the principle of the golden section method is introduced. Using the monitoring data of Pingyikou Tunnel, the mechanical parameters of the rock mass is back analyzed with the help of FLAC3D. The calculation process is optimized using the cyclic variable method and golden section method in the process of back analysis. The efficiency of the back analysis is improved, and the results of the back analysis are verified. It indicates that the precision of the method is high enough, and this method meets the requirement of back analysis.