Purpose The aim of this study is to investigate the horizontal displacement effects of foundation pit excavation on adjacent metro stations and shield tunnel composite structures. It seeks to develop a theoretical calculation method capable of accurately assessing these engineering impacts, aiming to provide practical assistance for engineering applications. Design/methodology/approach This study introduces a model for shield tunnel segments incorporating rotation and misalignment, considering the constraints of metro stations. It establishes a displacement model for tunnel-station combinations during foundation pit excavation, deriving a formula for calculating station-proximal tunnel horizontal displacements. The method's accuracy is validated against field data from three engineering cases. The research also explores variations in tunnel displacement, inter-ring shear force, misalignment and rotation angle under different spatial relationships between pits, tunnels and stations. Findings This study models uneven deformation between stations and tunnels due to bending stiffness and shear constraints. It enhances the misalignment model with station-induced shear effects and introduces coefficients for their mutual interaction. Results show varied responses based on pit-station-tunnel positioning: minimal displacement near pit edges (coefficients around 0.1) and significant effects near pit centers (coefficients from 0.4 to 0.5). "Whip effect" from station constraints affects tunnel displacement, shear force, misalignment and rotation, with fluctuations decreasing with distance from excavation areas. Originality/value This study demonstrates significant originality and value. It introduces a novel displacement model for tunnel-station combinations considering station constraints, addressing theoretical calculations of horizontal displacement effects from foundation pit excavation on metro stations and shield tunnel structures. Through validation with field data and parameter studies, the concept of influence coefficients is proposed, offering insights into variations in structural responses under different spatial relationships. This research provides crucial technical support and decision-making guidance for optimizing designs and facilitating practical construction in similar engineering projects.

Foundation pit excavation causes the deformation of adjacent tunnels,which in turn affects the safe operation of subway in tunnels.Therefore,how to accurately predict the deformation of adjacent tunnels is a problem worth studying.According to the non-limit earth pressure computational method,the earth pressure on the unloading pit wall during foundation pit excavation is calculated.With the aid of the Mindlin solution,the additional load acting on the side tunnel during the excavation stage of the foundation pit is obtained.The tunnel structure is considered as a Euler beam on the Winkler foundation beam and the differential equation of the elastic foundation beam is established.An analytical method for the horizontal displacement and deformation of the tunnel is given.Based on this method,the horizontal displacement of adjacent tunnels caused by foundation pit excavation is analyzed.The results show that the horizontal displacement of the tunnel increases with the increase of excavation depth of the foundation pit.The horizontal displacement of the tunnel calculated by considering non-limit earth pressure is relatively close to the value measured,and the overall relative error is smaller than 20％.Compared with the traditional method proposed,the author method is more practical.

计算基坑坑底隆起变形对下卧盾构隧道纵向变形的影响,建立基坑开挖引起的土体位移计算模型.引入转动与错台变形协调盾构隧道模型,基于影像源法,推导得到基坑开挖引起的下卧盾构隧道的纵向变形计算公式.结合3个实际工程监测数据,对比B-W,B-P法,验证计算方法的正确性,并对基坑坑底最大隆起量、基坑开挖宽度、开挖深度、隧道埋深这4个影响因素进行分析.研究表明:下卧隧道最大隆起值和基坑坑底最大隆起值呈正相关规律;随着基坑开挖宽度的增加,隧道隆起大小以及范围相应的增加;隧道埋深和下卧隧道隆起值呈非线性递减规律;减少基坑坑底隆起变形和隧道轴线方向基坑开挖宽度能有效控制下卧隧道纵向变形.

针对重叠盾构隧道施工引起土体变形问题,综合考虑了土体损失、开挖面附加推力、盾构机侧壁摩擦力和注浆压力4种因素引起的土体变形.对于掘进过程中土体损失引起的土体变形,修正了统一土体移动模型三维解,考虑了掘进过程中土质条件对纵向土体变形的影响,采用叠加法得到由于土体损失产生的重叠隧道施工土体变形计算公式;对于开挖面附加推力、盾构机侧壁摩擦力和注浆压力3种因素引起的土体变形,采用Mindlin解进行计算,并根据重叠隧道计算模型将上下线的计算公式进行叠加,得到考虑以上3种因素产生土体变形的计算公式;将公式进行组合,最终推导出重叠盾构隧道施工过程中多重因素共同作用下土体变形的计算公式.结合工程案例对该方法进行验证,对比发现:修正后的三维统一解适用的土质条件范围更广,且预测值更为吻合;考虑多种因素比仅考虑土体损失的预测结果更贴合实测值,证明了该方法的可行性.

归纳了 4种典型基坑围护结构变形模式下的基坑侧壁变形曲线计算方法,基于应力释放法,提出了一种考虑围护结构变形模式以及桩顶竖向荷载的邻近基坑单桩水平位移计算方法.分析了围护结构累计变形相同情况下,不同变形模式引起的邻近单桩水平位移规律,同时进行了 2个案例验证与影响因素分析.研究结果表明:在基坑围护结构最大变形相同情况下,悬臂型变形模式引起的邻近单桩最大水平位移最大,其次是复合型,再次是内凸型,踢脚型则最小;桩体最大水平位移与基坑围护结构控制参数虽然呈正相关规律,但是随着与围护结构水平距离的增加而呈非线性递减;作用在桩体上的附加应力增大时,桩体水平位移曲线逐渐从"悬臂"形向"鱼腹"形发展.虽然桩顶荷载对桩体水平位移有一定的影响,但是影响较小.

During the excavation of a foundation pit, differences in the stiffness of an enclosure structure with different supports may lead to different deformation modes of the enclosure structure. Without considering the effects of both pore-fluid and chemical reactions in the surrounding soils, the existing simplified analytical method is used to approximate pit sidewall deformation curves under four typical pit enclosure deformation modes, so that the horizontal displacement curves of a neighboring single pile are obtained by the image source method. Based on the results obtained from the simplified analytical method, it is concluded that both the maximum cumulative deformation value and the deformation pattern of a foundation pit enclosure structure can have nonnegligible effects on the horizontal displacement of the adjacent single pile. The maximum horizontal displacement of the single pile in the adjacent pit increases linearly with the control parameters of the pit enclosure structure, while it decreases nonlinearly with either an increase in the horizontal distance from the enclosure structure or a decrease in the excavation depth.

A prediction model of enclosure structure deformation caused by the excavation of foundation pit is established. Based on the virtual image technique, the soil deformation caused by sidewall deformation is calculated. Meanwhile, the deformation model considering rotating and staggering of shield tunnel is used to establish a calculation method of longitudinal deformation of adjacent shield tunnel. The result suggests that: (a) The horizontal displacement of adjacent shield tunnel is normally distributed. (b) With increasing retaining structure deformation, it is obvious that deformation value and range of adjacent shield tunnel also increase. (c) As the distance between the adjacent shield tunnel and the enclosure structure increases, the horizontal displacement of the side shield tunnel decreases nonlinearly. (d) The shield tunnel with shallow buried depth is greatly affect by the excavation of adjacent foundation pit. As the depth of the tunnel increases, the impact gradually decreases.

针对重叠盾构隧道施工引起的土体变形计算问题,将上下双线重叠隧道简化成单线隧道,提出等效大圆模型,基于三维统一解得到双线重叠隧道掘进引起的地表沉降以及土体水平位移计算公式.结合5个实际工程,将文中方法计算得到的地表沉降值与监测数据进行对比,验证了计算方法的正确性.研究表明在重叠盾构施工引起的土体变形研究中,采用等效大圆模型的计算方式是可行的;顶部与上线盾构内切的等效大圆为最优的等效模型.

In the process of foundation pit excavation, different retaining structures and support stiffness may lead to different deformation modes of retaining structures. The soil displacement cause by the deformation of the retaining structure is calculated by the virtual image technique. Meanwhile, the collaborative deformation model for rotation and dislocation is introduced to analyze the tunnel longitudinal deformation caused by different deformation modes as well as the tunnel maximum displacement equivalent field, and two case verifications are carried out. The study shows that there is a large difference in the size and distribution law of the soil displacement field caused by different enclosure structure deformation modes. The horizontal displacement of soil caused by the cantilever type always shows a "cantilever type" curve with increasing horizontal distance from the enclosure structure, while the composite type, inner convex type and kicker type develop from the "bow" to the "cantilever type" curve. The vertical displacement field of the soil is in the shape of a "spoon" and the soil exhibits a certain bulge deformation below the critical depth. The critical depths of the composite type and inner convex type are similar, while the kick type is the largest and the cantilever type is the smallest. The influence area of the maximum horizontal displacement of the tunnel outside the pit of the inner convex type and the composite type is basically the same. The influence area of the cantilever mode is the smallest, while the influence depth of the kick-in mode is higher than that of the other three deformation modes.