Abstract
Due to the limitation of geological conditions and route alignment, tunnel engineering will inevitably pass through special sections such as shallow buried section, broken rock layer, and loss and weak rock stratum. Tunnel construction in these special sections will easily lead to tunnel collapse, landslide of portal slope, excessive deformation of supporting structure, and even deformation and damage accidents, which are high-incidence areas of engineering safety accidents. In this paper, a 3D numerical model is established based on a practical engineering to analyze the deformation and stress variation of surrounding rock of the tunnel with the in-advance support technology. According to the monitoring results of the actual project, the deformation law of the soft rock section at the tunnel entrance is mastered. The deformation of surrounding rock of the tunnel under the support condition of changing the three main parameters, such as ring spacing, pipe diameter, and pipe length, is analyzed, and the effect of controlling the deformation of surrounding rock with different parameters is studied. The deformation, stress characteristics, and plastic zone distribution of surrounding rock by a single side wall guide method and ring excavation and retaining core soil method in advance support are numerically simulated and studied.
Highlights
When the tunnel passes through the mountain, it will be inclined to cross with the mountain with an asymmetrical terrain and inclined angle, resulting in asymmetrical load of rock mass on the tunnel
In the tunnel construction in these sections with poor geological conditions, in order to ensure the smooth completion of the project, in-advance support technologies such as shed pipe, small duct, and the horizontal rotary jet grouting piles should be adopted to control the deformation of surrounding rock [4]
Calculated Monitoring value Relative error value Relative error value Relative error of the three monitored sections are close to the field monitoring values, and the error is less than 15%, which indicates that the numerical simulation results are reasonable
Summary
When the tunnel passes through the mountain, it will be inclined to cross with the mountain with an asymmetrical terrain and inclined angle, resulting in asymmetrical load of rock mass on the tunnel. The limit equilibrium zone width, fracture zone width, and safe staggered distance of upper and lower coal seams will be determined according to the above theoretical equation, and the bolt support design plan will be optimized. In combination with the actual engineering situation, it is found that the support effect of the roof of the mining roadway is realized through the formation of “combined arch of anchoring layer” by anchor rods, so the “combined arch theory” is adopted for analysis and calculation [16]. In combination with the engineering practice and construction experience, considering the roadway cross section size, the row spacing between the sidewalls is 900 × 900 mm. In combination with the engineering practice and construction experience, considering the roadway cross section size, the row spacing between the roof and anchor is 1200 × 1200 mm. In order to meet the requirement of support strength, the bolt diameter is 20 mm
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