Study On Tunnel Face Stability In Dry Sand

Shield method on the basis of their economic, efficient, and the advantages of the minimum impact on the environment in the construction of urban subway tunnel and underground engineering is widely used. Carried on the tunnel construction by shield method, the reasonable control of the excavation face support pressure, guarantee the excavation face stability is the key to the design and construction. So for shield tunnel excavation face stability research has certain practical significance.The dry sand tunnel face stability by 1g model test and theoretical study and the comparison of practical engineering to evaluate with Particle Image Velocimetry was studied in this paper. The following aspects were included in the main contents:(1)Introducing the Particle Image Velocimetry(PIV), and based on the MATLAB platform to develop a new MPIV image processing software, and the principle of PIV technology and MPIV software is described in combined MPIV analysis software for the back of the model test to provide technical support.(2)The stress and strain gauge and MPIV image processing software, the buried depth ratio 0.5, 1.0 and 2.0 of surface subsidence rule of three conditions, excavation surface load and limit support pressure, excavation surface buckling shape and mode of study. Test used symmetric model and the non-instrusive measurement, by moving the piston displacement controlling experimental study.(3)By using FLAC3 D three-dimensional finite difference numerical simulation software, the small size of 1 g model test results validated the analysis. By comparing the verification, to prove and desirability of model test of the reliability of the numerical model and parameters selection. By using GEO limit analysis numerical simulation software, the excavation surface buckling shape and instability mode and safety coefficient are studied.(4)Based on the limit equilibrium method through the use of 3D wedge body model to simulate the excavation surface limit support pressure calculation, and use the relevant software writing formula to explore different embedded depth of C, heavy, angle of internal friction and cohesion of c and the influence of the surface P for the limit support pressure overload, general conclusions.