Weak Rock Tunnel Dynamic Construction Design And Construction Methods

The design concept of tunnel structures based on the principles applicable to ground works is limited and some technical parameters determined by engineering analogy is blind due to complicated hydro-geological condition characterized by tunneling and underground works. The observational design is a kind of method for tunneling design just under such background. It is necessary for its theory and practical technique studying to be carried out further since the observational design has being developed as a whole. The main contents of this studying cover the following aspects by taking the design theory, method and practical technique into consideration:(1)Some key problems existing in observational design and practical technique are studied, such as information collecting and processing, programming of monitoring technique, establishing of data database for engineering analog and classifying of surrounding rock. In addition some opinions and suggestions are put forward.(2) Prediction model of measured deformation is established with mathematic statistics, time series analysis and grey system model. Least square method is adopted in regression analysis, AR(n) model in time series analysis and GM(1,1) model in grey system prediction.(3) Grey system model for rock stability classification is established with grey correlation analysis. In this model, the reference number series are composed of stability indices of surrounding rock to be classified; while comparison series are composed of standard indices for classification. Based on this model, procedure for stability classification of surrounding rock is programmed and applied in Songjie-ya II tunnel, with the classification results basically tally with the measured at site.(4) According to the principle of tunnel dynamic construction design, a real projection was designed. Due to complex geohydrologic environment, there are many uncertainty influencing factor in tunnel, therefore, it is necessary and feasible to adopt dynamic design and construction in tunnel. In addition, due to the complexity of engineering environment and construction, and the inherent defaults of fitting functions, it is less accuracy and more error to fit some data. In this paper, section fitting was used and the accuracy was improved.(5)Field monitoring is a good way to keep engineering construction succeed, and also an effective method to perfect engineering design and construction supervision. With in-situ monitoring data and supporting parameters of JieShenPo tunnel, this paper silmulates the informatization and construction procedures. Application process shows it is necessary and feasible.(6) The dynamic construction procedures of gross section method, underhand bench method and CD method had been simulated in numerical methods. The results show that the CD method should be adopted in priority to other methods; the next is underhand bench method; it should take cautions to gross section method.In the end, it introduces the main conclusion and existing problems as well astechnical expectation. Furthermore some viewpoints and opinions are presentedherewith.