Abstract:

The end soil reinforcement of pipe jacking launching and arrival is the key to successful tunnel construction. In this paper, the formula of stability coefficient is given when the longitudinal thickness of reinforced soil is greater than the height of the tunnel entrance, which is an improvement for the existing sliding instability theory; and then three dimensional FEM is used to calculate the surface settlement when the Hsteel support is removed and when the shield crossed the reinforced area. Finally, the orthogonal experiment method is adopted to analyze the influence of longitudinal thickness of reinforced soil, the strength of reinforced soil and the thickness of cover on reinforcement effect of end soil. The results show that: 1) The thickness of cover and the strength of reinforced soil affect the maximum ground surface settlement slightly; but the thickness of reinforced soil affects the maximum ground surface settlement greatly. 2) The maximum ground surface settlement can be reduced by increasing the longitudinal thickness of end soil. 3) The thickness of cover is negatively correlated to the stable coefficient of end soil; and the thickness of reinforced soil and strength of reinforced soil is positively correlated to the stable coefficient of end soil. The results can provide an effective way to decide the scheme of end soil reinforcement in the future.

Key words: pipe jacking, end soil, orthogonal experiment, reinforcement effect, sliding instability theory