地铁施工对邻近桥梁桩基础内力影响分析

Influence of Metro Construction on the Internal Force of Adjacent Bridge Pile Foundations

文章采用数值方法研究了城市盾构隧道施工对邻近桥梁单桩、两桩、四桩基础的应力与位移的影响,研究结果表明:(1)隧道施工使单桩近隧道侧轴向应力减小,远隧道侧轴向应力增大,其影响程度随桩与隧道水平距离的增大而减小;(2)隧道施工下穿两桩或四桩群桩基础后,桩身近隧道侧轴向应力增大而远隧道侧轴向应力减小;(3)隧道施工对群桩的影响远大于单桩,其中距隧道较远桩顶两侧应力差在隧道施工后显著增大,承台距隧道较近时远隧道桩上部混凝土可能承受拉应力作用;(4)桩竖向位移随桩与隧道距离增大而减小,若桩底位于隧道底面以下,则隧道施工后桩产生较小沉降值;(5)桩受隧道施工影响一般在桩顶水平位移最大处,桩与隧道较远时位移值随桩深线性减小,较近时呈非线性减小趋势,其中桩上部位移沿桩深减小较快,桩下部位移收敛到定值,桩顶位移在桩与隧道一定距离时最大。

This paper studies the influences of urban shield-driven tunneling on the stresses and displacements of adjacent bridge foundations with one, two or four piles using numerical methods. The results show that：1） the axial stress of a single-pile foundation at the side nearest the tunnel decreases while that at the side farther away from tunnel increases, and the influence decreases with an increase of horizontal distance between the pile and tunnel; 2） the axial stress of a two-pile or four-pile foundation at the side nearest the tunnel increases while that at the side farther away from the tunnel decreases; 3） the influence of tunnel construction is greater on the grouppile foundation than on the single-pile foundation, for which the stress difference between the two sides at the top of the pile farther from the tunnel increases significantly after tunnelling, and concrete on the upper part of the pile farther away from the tunnel may be subjected to tensile stress when the pile cap is close to the tunnel; 4）the vertical displacement of the piles decreases with an increase of distance between pile and tunnel, and the settlement induced by tunnelling will be relatively small when the pile bottom is located below the tunnel floor; and5） tunnelling has the greatest impact on the horizontal displacement of the top of a pile. Specifically, the horizontal displacement decreases linearly with an increase of pile depth when the pile is far from the tunnel, while it decreases nonlinearly when the pile is close to tunnel. The displacement at the upper part of the pile decreases rapidly with an increase of pile depth, and the displacement at the lower part converges to a constant, while the displacement at the top of the pile will peak at a certain distance between the pile and tunnel.