| The construction of the Sichuan-Tibet Railway is of great significance for improving the conditions of the transportation infrastructure along the line and promoting the economic and social development of Tibet.There are many tunnels with a length of more than 30 km,and some tunnels are even longer than 40 km.At present,there is no experience in control measurement of more than 40 km railway tunnel construction for our country.In view of this,this thesis has carried out corresponding experimental research and discussion on some key technical issues in the plane control measurement of the super-long railway tunnel.The research content mainly includes the following aspects:First,this thesis analyzed the main sources of the angle measurement error of the horizontal control network in the tunnel,and the simulation calculation experiment of the horizontal control measurement and the lateral piercing error in the super-long railway tunnel is designed.Considering the influence of the centering error and other observational value errors,for the three types of network tunnel inner plane control networks of loop traverse network,cross traverse network and free-station linear-angular intersection network,this thesis calculates the lateral piercing errors in the tunnel for 7 kinds of lengths of railway tunnels within the range of 20～44km under the circumstance of 1 " and 1.3" horizontal angle measurement accuracy.And according to the simulation calculation results,the recommended value of the allowable value of the lateral piercing error in the tunnel are given for the seven types super-long railway tunnel of lengths of 20～44km under two angle measurement accuracy circumstances.Second,this thesis introduced the north-seeking theory of the suspended belt gyroscope,designed and carried out azimuth angle measurement experiment of the control network in the tunnel based on the CGTY-2 gyro total station,elaborated and summarized method and precautions of the gyroscope azimuth angle measurement,the internal and external coincidence accuracy of the gyro azimuth observed by the CGTY-2 gyro total station in this experiment is calculated and analyzed.The results of this study has guiding significance on how to add the gyro azimuth to the plane control network in super-long tunnel.Third,this thesis analyzed the influence of the vertical deflection on the horizontal observation value of the total station,and a simulated tunnel inner and outer plane control measurement experiment was carried out in a certain area of Tibet;the EGM2008 gravity field model was used to calculate the vertical deflection of the control points outside the tunnel.Whether considering the vertical deflection correction of the horizontal direction observation value of the total station on the connecting measurement of the tunnel or not,to analyze the influence of the vertical deflection on the accuracy of the side-point traverse network in the tunnel in the plateau area.Experiments have verified that when the height difference between the control points on the connecting measurement of the tunnel is large,it is necessary considering the vertical deflection correction of the horizontal direction observation value of the total station,to improve the accuracy of the side-point traverse network in the tunnel and reduce the lateral piercing error in the tunnel.Fourth,designed and carried out the plane control survey simulation experiment in the super-long tunnel,which mainly includes the design of the control network,the determination of the observation accuracy of the experimental control network,and the selection and burying of control points.By repeatedly measuring the cross-traverse network laid on the road of the experimental site to simulate the horizontal control network of the super-long tunnels,the actual measurement accuracy of the horizontal angle and horizontal distance of the crosstraverse network in the simulated tunnels of different lengths and the horizontal piercing accuracy after adjustment are calculated and analyzed. |
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