Study on Influence of Construction Sequence in Shallow Tunnel with Bias and Small Net Distance Based on Numerical Simulation
For the shallow tunnel of Qizishan with small net distance bias,the typical locations of the tunnel were selected to establish a fine three-dimensional model,and the tunnel construction process un-der different construction sequences was simulated.The effects of three different construction sequences of bias side first,bias side second and simultaneous construction on the formation deformation and struc-tural stress were studied,which provided a basis for the determination of construction sequence.The re-sults show that the first construction on the bias side causes the largest stratum displacement,followed by the simultaneous construction,and the last is the backward construction on the bias side.The maxi-mum variation of the vertical and horizontal displacement of the stratum caused by the construction se-quence is 15.50%and 62.50%respectively,and the maximum variation of the internal force of the supporting structure is 22.63%.Considering that the formation displacement and structural force varia-tion caused by the change of construction sequence are within the allowable range,the on-site construc-tion of Qizishan tunnel adopts the scheme of simultaneous tunneling of left and right lines,and the cons-truction process and monitoring data verify its rationality.
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