考虑地下水位升降影响的盾构施工诱发地层变形和衬砌响应分析

Analysis of stratum deformation and lining response induced by shield construction considering influences of underground water level rise and fall

盾构隧道施工时遭遇地下水位急剧变化会明显增大施工风险,既有成果较少考虑地下水位升降给盾构隧道施工带来的影响,也较少针对隧道衬砌本身变形和应力进行分析。在考虑盾构隧道施工时地下水位变化的情况下引入隧道洞周的非均匀收敛变形模式,采用复变函数法理论,提出地下水位升降影响下盾构隧道开挖引起的周围地层、衬砌变形和应力的计算方法。将理论解析结果与数值模拟结果进行对比,验证了所提出方法的可靠性,并针对衬砌厚度、隧道半径、地下水位深度等参数进行了敏感性分析。研究结果表明,衬砌的径向位移形态基本呈现'苹果把'朝上的'苹果'形;随着地下水位的下降径向位移由'鸭蛋'形逐渐向'苹果'形过渡,且'苹果'形越来越明显;衬砌的环向位移基本形态呈倾斜的'苹果'形,随着地下水位的下降倾斜的'苹果'形范围逐渐变大;径向应力的分布在衬砌厚度、隧道半径的影响下呈现出相同的增减变化规律,且随着上述两个参数逐渐增大,径向应力分布由水平放置的'鸭蛋'逐渐变化成水平放置的'?'字形,随着地下水位的下降径向应力形态逐渐向中心收缩;衬砌环向应力随着衬砌厚度的增大,应力略微减小,随着隧道半径的增大衬砌环向应力明显减小,随着地下水位的下降环向应力分布形态由竖立放置的'鸭蛋'形逐渐变化为竖立放置的'8'字形;衬砌切向应力在衬砌厚度、隧道半径的影响下呈现相同的增减变化规律,且切向应力分布呈现'苹果把'朝下的'苹果'形。研究成果可为地下水位变化明显的盾构施工控制提供参考。

A high risk will be raised when the groundwater level changes dramatically during the construction of shield tunnel.However,the impact of fluctuation of groundwater table is seldom considered in the construction of shield excavation in current studies.Besides,the deformation and stress analysis of tunnel lining are paid even less attention.The non-uniform convergence deformation at the periphery of the tunnel cavity is introduced into this paper,considering the fluctuation of groundwater level when the shield tunnel is being constructed.The complex functions are applied in calculating the deformation of ground and lining and stress caused by shield tunnel excavation under the influence of the variation in groundwater table.The presented method is proved to be reliable by comparing the theoretical analysis results with the numerical simulation results.In addition,sensitivity analysis of parameters such as the groundwater level depth,thickness of lining,radius of tunnel is carried out.The results show that the radial displacement of the lining presents a stem-upwards'apple'shape.When the groundwater level decreases,the radial displacement gradually transforms from'duck egg'shape to'apple'shape that tends to be more and more obvious.The circumferential displacement of the lining likes an inclined'apple'.With a decline of groundwater level,the range of the oblique'apple'expands.Under the influence of lining thickness,tunnel radius etc.,the distribution of radial stress shows the same variation rules as mentioned above.With the increase in these two parameters,the distribution of radial stress gradually changes from the horizontal'duck egg'to'?'shape.As the groundwater level drops,the shape of radial stress shrinks towards the center.The circumferential stress of the lining decreases slightly with an increase in thickness of the lining.While it decreases obviously with an increase in the tunnel radius.As the groundwater level drops,the distribution of circumferential stress gradually changes from the vertically placed'duck egg'shape to the'8'shape.The tangential stress of the lining shows the same variation rules under the influence of lining thickness and the tunnel radius.The distribution of tangential stress shows a stem-downwards'apple'shape.The research results can give a reference to the shield construction when the groundwater level changes obviously.