Study On Temporal And Spatial Effect In Construction Of Weak Surrounding Rock Tunnel

Excavating in the rock tunnel, it is continue to be disturbed by the construction of stress release, causing the deformation of surrounding development, and strength of support grow with time, the deformation of the rock getting more and more obviously inhibition.This article introduced the effects of temporal and spatial of geotechnical materials, rheological theory and time characteristics of concrete retaining structure (creep and elastic modulus change with time and other factors).Relying on construction works and other monitoring data tunnel to draw out the rock at different times with different load release rate, then choosing viscoelastic D-P and generalized Kelvin style model, using the finite element method soft rock tunnel construction process of the temporal and spatial effects of the numerical analysis. And the first attempt in the calculation taking into account the rheological properties of rock and concrete support growth characteristics of strength, dynamic simulation of the upper and lower level construction method steps. Main draw the following conclusions:(1) Relying on the tunnel projects, analyzed and gradeⅣRock Tunnel in the first 20 days in the week convergence of basically stable. Summarized by the construction offering time period corresponding to the different rock pressure release rate.(2) Using elastic-plastic constitutive model, ignoring strength rock rheology and supporting analysis of the growth process, the surrounding parts of the characteristic values calculated displacement is small, a large deviation of the actual monitoring results; and considering the rheology of rock and structure at different times corresponding to different strength characteristics, the calculated results agree well with the measured data can reflect the effect of the construction process of the time and space. Therefore, when soft rock tunnel design and construction of the simulation time factor to be included on the structure.(3) Dimensional analysis show that the tunnel excavation tunnel face displacement monitoring points near the convergence rates were higher, but the supporting role of space near the excavation face, the stress values are small, the flow surrounding the cutting face effect is not obvious; remote from the working face at (1.5D above), the characteristic part of the stress is large, and the surrounding convergence rate is smaller, the spatial effect of the basic excavation face away from the excavation face about 1.5D～2.0 D disappearing.(4) In the earlier tunnel construction, the value of each feature point displacement is more severe, the maximum rate of change in displacement basically appear in the first 3 days, the cumulative value of the deformation accounted for about half of the total. Support structure within the first 3 or 4 of the stress of rapid growth. In this stage, the effective elastic modulus of sprayed concrete was less than 40% of final value, obviously the worst cross-section support occurs during the first 3 days after. Therefore, it is recommended to strengthen the cross-section from the tunnel face 0.5D～1.0D at the construction management and monitoring.