盾构近距穿越桥梁施工对地表及桥梁桩基的影响

结合某地铁区间隧道盾构施工近距穿越桥梁桩基的复杂条件,选取桥台与桥墩基础影响最大断面,对盾构施工引起地表沉降及桥梁桩基的变形、应力及内力进行三维数值模拟计算。结果表明:①双线隧道盾构推进引起地表最大沉降位于双线隧道中间某处,大于单线隧道引起的地表最大沉降,地表沉降随着两条隧道间距的减小而增加;②右线隧道盾构施工引起B0C0桥台桩基近隧道边桩产生的最大变形与内力均发生在距桩顶13 m处,最大横向挠曲变形、纵向挠曲变形分别为2. 0、4. 8 cm,边桩内力致使桥台桩基超出承载能力,承台发生倾向隧道一侧的倾斜和水平面内扭转,严重影响桩基的安全;③双线隧道盾构施工引起B7C7桥墩桩基近隧道边桩桩顶处产生最大位移,最大横向水平位移、纵向水平位移分别为2. 6、5. 2 cm,右侧桥墩桩基承台产生的最大横向水平位移、竖向位移、纵向水平位移分别为3. 2、3. 4、4. 6 cm,承台发生倾向隧道一侧的倾斜和水平面内扭转,倾斜值为0. 001 8,接近规范规定的允许值,盾构施工时须引起注意。基于上述分析结果,提出盾构近距推进时的施工监测及施工参数调整的建议。

Influence of Adjacent Shield Construction Crossing the Bridge on Ground and Bridge Pile Foundation

Combined with the complex conditions of shield construction for subway running tunnel with a short distance crossing through the bridge pile foundation, after selecting the maximum influence section with the abutment foundation and the pier foundation, three-dimensional numerical simulation and calculation were conducted, including the ground surface settlement and the deformation, stress and internal forces of the bridge pile foundation caused by shield construction. The results show that: (1) The maximum ground surface settlement caused by shield tunneling in the double-line tunnel is located somewhere in the middle of the double-line tunnel, which is larger than the maximum ground surface settlement caused by the single-line tunnel. And the maximum ground surface settlement caused by shield tunneling in the double-line tunnel increases with the decrease of the distance between the two line tunnels. (2) The maximum deformation and internal force of the side pile near the tunnel caused by shield construction on the right line occurs at 13m away from the top of the pile, the maximum lateral deflection deformation and vertical deflection deformation of the side pile is 2.0cm and 4.8cm, respectively. the insufficient bearing capacity of pile foundation is produced under the function of the internal force of the side pile caused by shield construction, and the inclination with the side of the tunnel and the torsion in the horizontal plane of the pile cap will occur, which will affect the safety of the pile foundation. (3) The maximum displacement of the side pile near the tunnel caused by shield construction in double-line tunnel occurs at the top of pile. The maximum lateral horizontal displacement and vertical horizontal displacement of the side pile is 2.6cm and 5.2cm, respectively. The maximum lateral horizontal displacement, vertical displacement, and vertical horizontal displacement of the pile caps on the right side piers caused by shield construction is 3.2cm, 3.4cm, and 4.6cm, respectively. The inclination with the side of the tunnel and the torsion in the horizontal plane of the pile cap will occur, the inclination value is 0.0018, which is close to the allowable value specified in the code. The shield construction must be pay attention. Based on the above analysis results, some suggestions on the construction monitoring and the adjustment of construction parameters during shield tunneling are proposed.