The Integrated Application Of Time Series Analysis To Measurement Of Displacements In A Tunnel

Monitoring control and survey is an important component in NATM tunnel construction, which can provide basis for estimating design scheme, investigating changes of surrounding rock and confirming supporting structural forms, also in good time propose secure information about stability degree of surrounding rock and supporting structural reliability to foresee accident and danger. Displacement monitor of tunnel is a part of main contents in monitoring control and survey, so it plays an important role in tunnel construction and optimum design. Based the method of time series analysis, monitoring data of tunnel displacement is modeled and analyzed, from which the main studying productions are listed as follows:â‘ Mixed model that is suitable for monitoring data of tunnel displacement is established. It not only incarnates physical meaning of studying object, but also contains system's characteristic.â‘¡In view of the fact that estimate of model's parameters is the most critical part in time series, model estimate precision and good or bad results determine straightly choice of model and prediction accuracy. Aim to characteristics of nonlinear parameter estimation in autoregressive moving average model, it is brought forward that parameter estimation is divided into two steps: the first step is parametric preliminary estimation, the second step is parametric precision estimation. Firstly MALAB self-made program on parametric preliminary estimation and parametric estimation program of EViews software are applied respectively; parametric estimation value of which has less RSS is selected as new preliminary estimation. Then MALAB self-made program on parametric precision estimation is used to solve parametric precision estimation value.The result indicates that the method improves precision of parametric estimation and predictive effect largely.â‘¢Selection of model includes two parts: model's order determination and diagnostic test. Through adopting various order selection criteria and statistical tests, the best model is found out. When analyzing example, different modeling methods of time series are used to model, whose results are analyzed and compared, then it is the most possible to choose low-order model having less parameters.â‘£Monitoring data of tunnel displacement is analyzed in terms of time series model with this method, meanwhile short-term predict, recovery of data and comparison of models are carrying out, finally appropriate model of time series is gained, which has better approximation effect, goodness of fit and accuracy, also provides the basis for instructing construction practice and modifying design of support system.