Study On Monitoring Technology For Underground Tunnel And Dynamic Model For Surface Settlement

In this dissertation, the modem monitoring technology based on the advanced theories on underground tunnel is provided; the precision control methods and measures are systematically discussed; the direction guidance system of shield tunneling and the dynamic forecasting models of ground settlement are introduced. The main contents are as follows:(1) The measurement data processing theory and the design scheme of GPS tunnel control network are introduced; A wavelet analysis technique that can efficiently reduces the multi-path effects caused by tall buildings is presented; Finally, the factor sources of transfixions errors of underground tunnel and limit error distribution method which depends on unequal influence principle are proposed.(2) The technology, accuracy, reliability of underground monitoring and control surveying are discussed. The influence factors and optimal scheme of connected-triangle surveying with shaft is analyzed in detail. The formula for calculating the lateral transfixion errors of underground traverse with added gyro orientation line is derived strictly, the calculation results show that the accuracy can be increased obviously by the way of orienting added gyro lines. The optimal position of added a gyro orientation line and increment rate of accuracy is provided.(3) The precise direction guidance system of shield tunneling is studied. The direction guidance system plays an important part in the shield excavation, such as the prevention of snake motion, the reduction of ground settlement of tunnel construction and the insurance of tunnel quality etc. Based on the principle of guidance system, a precise direction guidance system with high accuracy, high efficiency and more reliability is developed, it has the advantages of less times of surveying, real time positioning and shield behaviors monitoring. The accuracy estimation methods of the guidance system are discussed in detail. The practical application in underground tunnel shows the system availability and great practical value.(4) The dynamic data forecasting model of ground settlement is studied, a new prediction model of grey-time serial with time-varying parameters characters is proposed. Based on the analysis of the shortcoming of the classic grey model, an improved grey model with time varying parameters is presented. An improved AR model is studied, which established by the combination normal order time serial and contrary order data in case the observations are less, and then, the combination model with improved grey and time serial is introduced. It can reflect not only the deformation tendency, but also the stochastic characters. It is very suitable to be applied to deformation analysis and prediction. Finally, the effectiveness and accuracy of ground settlement predicting in a practical underground construction with the combination model are validated.(5) The NN(Neural Network) prediction model of ground settlement in the shield tunneling is proposed. Firstly, the shortcomings of the back propagation algorithm, such as slow learning speed and local minimum points, are discussed. Then an improved hybrid model with fast convergence rate, good performance based on combination of the genetic algorithm and the BP algorithm is presented by improving real coding, genetic operators etc. Finally, the prediction models of NN and FNN(Fuzzy Neural Network) are tested in shield tunneling, and the experimental results show the model has the higher forecasting accuracy. Then the conclusion is drawn that this method is an effective way of solving prediction problem of tunnel construction.