| In recent years, along with our country the development economy, the highway tunnel engineering and technical level of China is the development by leaps and bounds.Due to the multi-arch tunnel can better adapt to the special terrain, mountains linear fluid,Multi-arch tunnel, more and more adopted by designer. Take Hubei swan multi-arch tunnel as the background, the tunnel of bias construction process are numerically simulated using finite element software MIDAS/GTS.Through the research on rule of surrounding rock and supporting structure stress-strain of change, optimization analysis the different excavation scheme and excavation sequence. Combined with monitoring measurement of grey modeling, use Matlab to predict the monitoring data. The main research results of this paper are:(1)Using the three heading construction, the maximum stress appear at the exit of the partition-wall in left side of the waist and feet for 9.0MPa;With central drift method in construction, after the excavation of left tube upper bench, the loose zone of inverted arch in the left hole and the formation of the central drift which had been excavated area overlapping to form an organic whole, slide easily happened, be sure to strengthen monitoring measurement, when the construction of tunnel middle wall stress value was 10.3MPa.Using three heading construction, final settlement of left and right holes is 12.25 mm, 10.09 mm, and use the pilot tunnel construction, left and right holes final settlement value of 13.14 mm, 10.95 mm.Using three-pilot method to excavate the tunnel,the vaults, waist and bottom middle wall stress value were 4.6MPa, 2.56 MPa and 3.0MPa, which was less than 5.0MPa, 3.0MPa and 3.0MPa when using the central drift method.So, two side heading excavation can release part of the surrounding rock pressure,effectively reduce the stress of the middle wall.(2)On the mid-partition is concerned,the minimum small primary stress value of 11 MPa of working condition I is less than the minimum small primary stress 12 MPa in the condition II,for middle wall maximum principal stress,the working condition I of 1.2MPa is less than the maximum 2.8MPa of condition II;From the point of initial lining stress distribution,the maximum displacement value of the working condition I and working condition II respectively, 24.97 mm, 19.23 mm, primary lining maximum tensile stress is 1.1MPa, 2.1MPa, respectively, the largest compressive stress is 8.4MPa and 10 MPa, respectively.As the plastic zone from the surrounding rock shows, the working conditions I mainly plastic zone distributed on both sides of the arch at the waist and the top of the wall, condition II of plastic zones located in the side walls and the sides of the arch at the top of the bias at the waist.(3)In the ZK72+755 section, level convergence, vault subsidence, inverted arch settlement prediction were respectively 20.98 mm, 7.49 mm and 10.50mm;Through the field monitoring measurement,ZK72+755 section of the measured values were 21.00 mm, 7.68 mm and 9.45 mm respectively. Equation to predict, therefore, was close to measured values, can be seen, the gray GM(1,1) model could accurately simulate the surrounding rock displacement of time sequence, prediction accuracy had reached the requirement of tunnel safety construction.(4)The swan multi-arch tunnel vault subsidence, horizontal convergence and inverted arch sedimentation stability displacement were:15.0mm,5.0mm and8.0mm, stable time required for about 35 days.Vault subsidence and inverted arch sedimentation value was bigger.The contact pressure of surrounding rock and initial lining would gradually increase along with the excavation of the tunnel face. 35 days after the excavation, the pressure value of monitoring point tend to be stable, the left spandrel stress basically was greater than the right spandrel. |
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