Analysis On The Stability Of Surrounding Rocks And Its Safety Guarantee Measures In Qingdao Close Overlapping Underground Engineering

As an important topic in the net wise of the urban subway, the surrounding rocks and the tunnels' stability and safety in close overlapping underground engineering were discussed in this paper. Based on the classical geometry conditions and construction environment ofQingdao overlapping tunnel engineering, by the application of theory analysis and numerical simulation methods, the construction technology problems are studied from four aspects: affecting factors of displacement, deduce of model formulation, displacement control measures and optimization of the construction method. The exact content of the four aspects are described in detail next. Firstly, the factors affecting the stability of the surrounding rocks and the displacement of the tunnel liners in the close overlapping engineering were analyzed and also sorted by their importance, which identify the affecting degree of each factor and the affecting laws of them. And the calculation formulation of the deformation trough at the liner bottom of the existing tunnels was fitted, which compared with the simulation results demonstrated that it can function as a substitute for the numerical simulation program to estimate the maximum settlement of the liner bottom of the existing tunnel. Secondly, based on the deformation features of the existing tunnel of close overlapping ones, by the application of flexible foundation beam theory, a new model was brought up and the calculation formulations of the settlement at the point of inflection of the existing tunnel liner and the maximum slope angle of settlement were deduced, which complement the present deformation theory of the existing tunnel liner in the close overlapping underground engineering, and their reliability and fair has been proof-tested by the numerical analysis. Thirdly, the deformation and destruction law of the close overlapping tunnels were summarized, according to which five consolidating engineering measures, as well as their separate consolidating effects and consolidating features, were simulated and analyzed. Then, by optimum combination, the engineering measures controlling the deformation of tunnels were proposed and the location of the movement joint in the existing tunnels was determined. Finally, by the simulation of the dynamic construction process of the new tunnel line respectively by three methods, the deformation features of the surrounding rocks and tunnel liners by each method were studied, and it was suggested to apply the step-CRD-step construction process to excavate the new line. and it was suggested to apply the step-CRD-step construction process to excavate the new line. And the step settlement control indexes of the liner crown of the existing tunnel by CRD method were made up, which will offer theory basis and technology support for the engineering construction.By all of the work done, the basic technical problems confronted during the passing process of the new tunnel across the existing one were nearly all covered. The deformation law of the surrounding rocks and liners of the engineering alike was concluded, and engineering measures and excavating methods that can effectively control the deformation were also listed. All of them offer advice and theory reference for the deformation control, support structure design and optimization of the excavation, assuring the safety of the construction and operation of overlapping underground engineering.