Highway Tunnel Structure Engineering Properties

In view of poor researches on stress characteristics of soil and lining in the loess highway tunnel, the paper analyses the performances of stress and deformation of soil and lining structure, the process of tunnel construction, and water infiltration influences, and makes field observation of stress features of lining structure and theory research of surrounding rock pressure.Directed against stress properties of lining structure of loess highway tunnel, the paper selects three loess highway tunnels as relying engineering according to buried depth and soil properties, and takes field observation synthetically for the first time, which pays more attention to researches on the change regulations of pressure acting on first lining and invert, axial force of lattice girder, contact stress between first and second lining, concrete strain of second lining verse the time and distributions in different positions. The observation results reveal the difference between surrounding rock pressures of shallow tunnel calculated by exiting methods and test results is large, pressure figure seems cat ear, surrounding rock pressure of deep tunnel belongs to clastic pressure, the test result is consistent with result by modified KAKE formula, the invert stress properties of shallow tunnel and deep tunnel are different, the axial force of lattice girder is at pressure in majority, and the stress of second lining is relatively small in loess highway tunnel.According to the properties of tunnel construction, the paper compiles the FEM program of numerical simulation, which reflects the excavation effects of tunnel construction and the contact properties between first and second lining. The paper analyses the influences of soil parameters in Duncan-Zhang model, lining concrete strength, lining size, concrete age and buried depth of tunnel on performances of soil and lining. The results show the calculating results are sensitive to soil parameters such as internal friction angel, cohesion, rigidity parameter k and initial tangential Poisson ratio, the influences of concrete strength on the soil and lining are not large, there is rational and economical thickness of the lining, concrete age has large effect on lining axial force. The paper researches the effect difference of excavation length at one time on surrounding soil within the possible range of bench cut method through the compiled program.By use of the compiled program, the paper dynamically simulates the construction process of relying engineering, and compares these results synthetically, the results comprehensively reveal the influences of soil strength and buried depth on soil and lining. Selecting the shallow tunnel as engineering background, the paper adopts two simulation methods to analyze tunnel engineering properties in the situation of water infiltration, The results show water infiltration results in the increase of surrounding rock pressure, and deteriorates the safety condition of the lining, which is the main reason of loess tunnel diseases.On the basis of field observation results and effect properties analysis of the buried depth, the paper points out some problems with the exiting demarcation criterions of buried depth when they are used to loess highway tunnel, and firstly puts forward new thought and method through change regulation of soil lateral pressure coefficient in the center line, which is proved feasible by two engineering cases. In view of the large difference among the surrounding rock pressures calculated by different methods in the shallow soil tunnel, the paper draws the calculating formula of the pressure, and compares the results by the formula with the observation results of relying engineering, which proves the formula feasible.