Study On Application Of Total Station In Highway Tunnel Deformation Measurement

The monitoring of tunnel surrounding rock deformation is an important means of studying the stability of surrounding rock and support structure, and the indispensable and important work for ensuring construction safety and confirming reasonable support parameter of tunnel, also the connection point and essential step of tunnel design and construction. At present, Although total station has been used in monitoring tunnel surrounding rock deformation, the accuracy problem is not to be well solved comparing to the traditional measurement, so total station non-contact measurement is not to be widely used. To evaluate the measured accuracy of total station non-contact measurement, this paper takes comprehensive analysis of total station measured accuracy with two methods of field comparative test and accuracy calculation based on the projects of Dunliang tunnel and Yuanjiabian tunnel. The main research contents and results are as follows:(1) It takes arch crown comparative field measurement test based on Dunliang tunnel, and measurement methods of which includes contact measurement of level, RDM of total station and three-dimensional coordinate measurement of total station. It takes convergence comparative field measurement test based on Yuanjiabian tunnel, and measurement methods of which includes contact measurement of convergence meter, and RDM of total station and three-dimensional coordinate measurement of total station.(2) Monitoring results show that using total station to measure tunnel surrounding rock deformation can monitor the surrounding rock deformation which contact measurement is unable to do before the core soil excavated. Before the core soil excavated, the value of arch crown is 19.7mm, which is 17.7% of total arch crown in construction stage, and the value of clearance convergence is 11.1mm, which is 28.8% of total clearance convergence in construction stage; After the core soil excavated, the average monitoring windage of non-contact measurement of RDM of total station and level is 1.9mm, which is 1.7% of total arch crown in construction stage; the average monitoring windage of non-contact measurement of RDM of total station and convergence meter is 0.83mm, which is 2.3% of total clearance convergence in construction stage; the measured accuracy of RDM of total station is better than that of three-dimensional coordinate measurement of total station. (3) Accuracy calculation and analysis is carried on the tunnel construction process with the application of error propagation law of RDM of total station. The analysis results show that when measured accuracy of total station is up to " ms=2+2ppm, ma=1" ", and horizontal distance of backsight datum mark and monitoring section is between 50～150m, and also horizontal distance of monitoring station point and monitoring section is between 40～60m, monitoring accuracy of arch crown can be 0.43～0.68mm and monitoring accuracy of clearance convergence can be 0.47～0.79mm.(4) Through using total stations with different accuracy to monitor tunnel surrounding rock deformation, it shows that when measured accuracy of total station is up to " ms=2+2ppm, ma=2" ", monitoring accuracy of surrounding rock deformation can be less than 1mm.By comparing on-site monitoring data and calculation of accuracy, it shows that the non-contact measurement accuracy is within the allowable range. It makes station position more flexible, improves work efficiency, and can make parallel working with supporting procedure. The monitoring result is ideal.