地铁行车速度对盾构隧道运营沉降的影响分析

地铁行车荷载经轨道-道床-隧道结构传至地基，在土体内部产生循环动应力以及超孔隙水压力是引起盾构隧道沉降的重要原因。通过车-轨-隧道-地基竖向耦合动力模型分析隧道差异沉降对列车运行荷载的影响，以上海地铁一号线体育馆站附近区间隧道为工程背景建立三维数值模型，结合塑性累积应变及累积孔压经验公式进行计算，对比分析软土盾构隧道下卧土层有、无纵向差异沉降两种情况下，地铁行车速度对隧道运营沉降的影响。结果表明：列车运行速度越快，下卧土体波动越大，但衰减越快。地基差异沉降对其长期运营存在明显不利影响，随着列车速度增大，这种影响也愈加明显。当地基差异沉降小，轨道平顺条件好时，隧道长期沉降随地铁行车速度的增大而减小；当地基差异沉降突出，轨道存在明显不平顺时，隧道运营沉降随行车速度增大而显著增加。

Influence of subway train speed on operation-induced settlement of shield tunnel

The traffic load transfers from track, roadbed, and tunnel structure to foundation, generating cyclic dynamic stress and excess pore water pressure in soil, inducing settlement of shield tunnel. A vertical coupling dynamical model of metro train, track, tunnel and foundation is developed and used to analyze the effect of differential settlement of tunnel foundation on subway traffic load. A three-dimensional numerical model is established based on the engineering background of the subway tunnel near the Stadium Station of Shanghai Metro Line 1. Combined with the calculation formulas of accumulated plastic strain and cumulative pore pressure, the influence of train speed on the long-term settlement of subway foundation without tunnel uneven deformation is analyzed and compared to the case with tunnel differential deformation. It is shown that the larger the amplitude of soil vibration is, the faster the amplitude attenuation becomes while the train speed gradually increases. The longitudinal differential settlement has significant adverse effect on the operation of subway tunnel. As the train speed increases, this effect becomes more significant. When the tunnel differential settlement is small and the track condition is good, tunnel operation settlement decreases as the metro driving speed increases. However, the long-term settlement of tunnel significantly increases as vehicle speed increases, while the foundation differential settlement becomes pronounced and the track irregularities are significant.