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Analysis on the Support Effect of Advance Large Pipe Umbrella at Portal Section of Shallow Tunnel under Unsymmetrical Load
(1. School of Civil Engineering of Xi′an University of Architecture and Technology, Xi′an 710055; 2. Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering, Xi′an 710055; 3. Tunnel and Underground Structure Engineering Research Institute of Xi′an University of Architecture and Technology, Xi′an 710055; 4. The First Engineering Co., Ltd. of China Railway Beijing Engineering Group, Xi′an 710100; 5. China Road & Bridge Corporation, Beijing 100011)
Abstract The reasonable support measures for the portal section of shallow tunnel under asymmetric load are the key to achieving the safe construction of the tunnel portal. The portal section often encounters unfavorable geology such as shallow asymmetric load, strong weathering of mountain surface rock, and soft and broken surrounding rock,so it is necessary to use advance support measures to control the deformation of surrounding rock. The Tbilisi portal project of No. 4 tunnel of Lot F3 of E60 expressway in Georgia under construction is taken as the case to analyze the influence of the ADECO-RS excavation method with or without advance pipe-umbrella support on the ground settlement, extrusion deformation of tunnel face, pre-convergence deformation, convergence deformation, stress distribution of surrounding rock and the development of plastic zone of tunnel portal section by means of the numerical test method. The analysis based on the numerical test results shows that the advance pipe-umbrella support at the tunnel portal section can promote the formation of stress arch, improve the stress of the advance core soil, reduce the ex? trusion deformation of the tunnel face and the plastic zone range of core soil when the ADECO-RS method is used for construction. In the range of about one time tunnel diameter in front of and behind the tunnel face, the tunnel crown settlement rate is the largest, and the deformation amount reaches 85% of the total amount. At the same time,the advance pipe-umbrella support will greatly reduce the plastic zone range of surrounding rock and avoid the overall collapse of the tunnel portal caused by the plastic zone of surrounding rock in the shallow tunnel portal section developing to the surface.
Abstract：
The reasonable support measures for the portal section of shallow tunnel under asymmetric load are the key to achieving the safe construction of the tunnel portal. The portal section often encounters unfavorable geology such as shallow asymmetric load, strong weathering of mountain surface rock, and soft and broken surrounding rock,so it is necessary to use advance support measures to control the deformation of surrounding rock. The Tbilisi portal project of No. 4 tunnel of Lot F3 of E60 expressway in Georgia under construction is taken as the case to analyze the influence of the ADECO-RS excavation method with or without advance pipe-umbrella support on the ground settlement, extrusion deformation of tunnel face, pre-convergence deformation, convergence deformation, stress distribution of surrounding rock and the development of plastic zone of tunnel portal section by means of the numerical test method. The analysis based on the numerical test results shows that the advance pipe-umbrella support at the tunnel portal section can promote the formation of stress arch, improve the stress of the advance core soil, reduce the ex? trusion deformation of the tunnel face and the plastic zone range of core soil when the ADECO-RS method is used for construction. In the range of about one time tunnel diameter in front of and behind the tunnel face, the tunnel crown settlement rate is the largest, and the deformation amount reaches 85% of the total amount. At the same time,the advance pipe-umbrella support will greatly reduce the plastic zone range of surrounding rock and avoid the overall collapse of the tunnel portal caused by the plastic zone of surrounding rock in the shallow tunnel portal section developing to the surface.
SONG Zhanping1,
2,
3 PEI Jiafeng1 etc
.Analysis on the Support Effect of Advance Large Pipe Umbrella at Portal Section of Shallow Tunnel under Unsymmetrical Load[J] MODERN TUNNELLING TECHNOLOGY, 2022,V59(6): 86-96
2022, Vol. 59 