盾构隧道施工对邻近桩基础位移和受力特性的影响研究

发布时间：2018-11-18 21:43

【摘要】：摘要：随着经济发展和城市化进程的不断加快,城市地下轨道交通开始大量修建以缓解日益拥堵的地上交通,由于地铁一般沿城市的主干路修建,会不可避免的穿越桥梁的基础,使其产生位移并产生内力的重分布,影响结构的正常使用。本文以北京地铁10号线所穿越桥梁为主要工程背景,利用有限元方法来模拟不同工程地质条件、桩基形式、桩与隧道位置关系、隧道施工控制条件时隧道开挖穿越桩基础后,对桩身位移和受力特性的影响,得出主要结论如下： 1)桩沉降值随土体压缩性、泊松比、抗剪强度、桩与隧道距离的增大而减小,桩基嵌入深度大于隧道埋深时,沉降值随桩长增大而减小,两桩承台基础桩间沉降差和承台倾斜率减小。粉土层中隧道下穿单桩,桩位于隧道开挖面正上方附近时产生背离隧道方向倾斜,桩与隧道距离大于5m时产生向隧道方向倾斜,位于隧道轴线正上方时不产生倾斜；隧道侧穿后,水平位移沿桩深非线性分布,桩产生弯曲,土体抗剪强度越弱,弯曲变形越大,土体泊松比增大,桩弯曲方向由与隧道衬砌相同变为相反。两桩承台基础桩顶处倾斜方向与承台相同。 2)桩位于隧道结构正上方时,桩轴力减小,位于隧道结构侧上方时,轴力增大,影响程度随桩与隧道距离增大而减小,受土体抗剪强度、压缩性、泊松比变化影响较小。两桩承台基础中近隧道桩承受荷载减小,该部分荷载由远隧道桩承担,影响程度随桩嵌入深度增加而减小。 3)隧道下穿单桩后桩身承受附加弯矩较小,侧穿使桩承受较大弯矩,最大值一般位于与隧道轴线相同标高处,与桩和隧道距离有关,粉土层中其值为6m时最大,桩身近隧道侧正应力增大、远隧道侧减小,对桩深与隧道轴线同标高处正应力影响最大。附加正弯矩值和正应力变化量随土体泊松比、抗剪强度的增大而减小。两桩承台基础近隧道桩顶由于承台的连接作用承受较大的附加弯矩作用,该处远隧道侧混凝土承受拉应力作用。 4)地表沉降值与桩身沉降和水平位移间呈线性相关关系,与桩身轴力、弯矩、正应力值间呈非线性关系,地表沉降值增大,对桩内力影响程度增大,并且对其影响增大速率也呈增大趋势。基于以上分析分别给出了桩竖向和水平位移与隧道施工引起地表沉降、桩与隧道水平距离、桩长之间的函数关系式。
[Abstract]:Abstract: with the development of economy and the acceleration of urbanization, urban underground rail transit (UMT) has been built in large quantities to alleviate the traffic congestion, because the subway is built along the main road of the city. It will inevitably cross the foundation of the bridge, causing displacement and redistribution of internal force, which will affect the normal use of the structure. Based on the bridge crossing of Beijing Metro Line 10 as the main engineering background, the finite element method is used to simulate the different engineering geological conditions, the form of pile foundation, the relationship between pile and tunnel position, and the tunnel construction control condition. The main conclusions are as follows: 1) the pile settlement decreases with the increase of soil compressibility, Poisson's ratio, shear strength and the distance between pile and tunnel. The settlement value decreases with the increase of pile length, and the settlement difference between two pile caps and the slope ratio of pile cap decrease. When the pile is located near the tunnel excavation surface, the pile deviates from the tunnel direction, when the distance between the pile and the tunnel is larger than 5m, the pile tilts towards the tunnel direction, and does not tilt when the pile is located directly above the tunnel axis. The lateral displacement of the tunnel is nonlinear distribution along the depth of the pile, the pile is bending, the shear strength of the soil is weaker, the bending deformation is larger, the Poisson's ratio of the soil is increased, and the bending direction of the pile is changed from the same as the tunnel lining to the opposite. The inclined direction of the top of the two pile caps is the same as that of the cap. 2) when the pile is located directly above the tunnel structure, the axial force of the pile decreases, while the axial force increases when the pile is located on the side of the tunnel structure, and the influence degree decreases with the increase of the distance between the pile and the tunnel. The influence of the change of soil shear strength, compressibility and Poisson's ratio is small. In the foundation of two pile caps, the load of near tunnel pile decreases, which is borne by the pile of far tunnel, and the influence degree decreases with the increase of the depth of pile embedding. 3) the pile is subjected to small additional bending moment after single pile under tunnel, and the maximum value is generally located at the same elevation as the axis of the tunnel, which is related to the distance between pile and tunnel, and the maximum value in silt soil is 6 m, the maximum value is at the same elevation as the tunnel axis, and the maximum value is 6 m in silt soil. The normal stress of the pile near the tunnel side increases and the far side of the tunnel decreases, which has the greatest effect on the normal stress at the same elevation between the pile depth and the tunnel axis. The value of additional positive moment and the variation of normal stress decrease with the increase of Poisson's ratio and shear strength. Two pile caps near the pile top of the tunnel bear greater additional bending moment because of the connecting action of the cap, and the concrete in the far side of the tunnel is subjected to tensile stress. 4) the surface settlement value is linearly correlated with pile settlement and horizontal displacement, and is nonlinear with pile axial force, bending moment and normal stress. The surface settlement value increases and the influence degree on pile internal force increases. And the influence of the increase rate also showed an increasing trend. Based on the above analysis, the functional relations between the vertical and horizontal displacement of pile and the ground settlement caused by tunnel construction, the horizontal distance between pile and tunnel, and the length of pile are given.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U455.43

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