小净距左右不同跨度隧道施工对上部建筑物变形影响分析

Analysis of the Influence of the Construction of neighborhood Tunnel with Different Left and Right Span on the Upper Building Deformation

依托重庆市两江桥的渝中连接隧道,应用有限元软件ANSYS建立包括建筑物在内的3D隧道模型。分别计算小净距左右不同跨度隧道采用左洞先行的CD+弧形导坑预留核心土(工况Ⅰ)、左洞先行的超短台阶+弧形导坑预留核心土(工况Ⅱ)和右洞先行的CD+弧形导坑预留核心土(工况Ⅲ)施工方法对上部建筑物的位移变化规律。研究结果表明:在3种工况下,隧道施工对上部建筑物最不利影响发生在左右隧道交接阶段,上部建筑物的水平位移和竖向位移影响规律大致相同;相比工况Ⅲ,工况Ⅰ下的水平偏移量减少21.1%,沉降量增加0.2%,在工况Ⅱ中相应值为-19.44%、0.29%;建筑物沿高度方向的位移在隧道施工过程中逐渐增大,但增长速度减缓,工况Ⅲ中沿建筑物高度方向沉降增加量百分比分别为5.73%,9.32%,10.46%;当围岩较好、支护支撑合理、地表存在不对称荷载时,先开挖远离建筑物一侧的隧道更合理。

Based on the Yuzhong connecting tunnel of Chongqing city river bridge,this paper uses the finite element software ANSYS to establish a 3 D tunnel model,including the upper building.With the left hole excavated first of center diagram method and arc heading reserved core soil method（mode Ⅰ）,the left hole excavated first of the ultra short step method and arc heading reserved core soil method（modeⅡ） and the right hole excavated first of center diagram method and arc heading reserved core soil method（mode Ⅲ）,the displacement variation law of different left and right span of the neighborhood tunnel and the construction influence on the upper building are calculated respectively.The results show that under threeconditions the most adverse effect of the tunnel construction on the upper building occurs in the period when the left and right tunnels are interconnected.The influence laws guiding the horizontal displacement and vertical displacement of the upper building are roughly identical.Compared with the working condition Ⅲ,the horizontal offset under working condition Ⅰ is decreased by 21.1% and the settlement is increased by 0.2%,and the corresponding values under working condition Ⅱ are 19.44% and0.29%; the displacement along the height of the building increases gradually during tunnel construction,but the growth rate is slow; under working condition Ⅲ the percentages of settlement increase along the height of the building are 5.73%,9.32% and 10.46% Respectively; when the surrounding rock is good with proper support and unsymmetrical ground surface load,it should be more reasonable to excavate first the side of the tunnel farther away from the building.