基于壳单元的盾构隧道参数化结构计算与验证

Parametric structural calculation and verification of shield tunnel based on shell elements

三维壳单元较二维梁单元能更精细地模拟管片结构受土体作用下的力学行为。为了推广三维壳单元隧道结构计算模型在大直径盾构隧道结构计算中的应用,提出基于壳单元的参数化隧道结构建模方法(Shell element-based Parametric Tunnel Structure Modeling,SPTSM)。SPTSM基于隧道中轴线及截面半径参数,能自动生成由壳单元所组成的隧道模型。在模型中,相邻环之间的壳单元公共边被定义成线性铰,以此模拟管片环缝间的接头刚度;管片纵缝间的接头刚度通过均质圆环法引入折减系数进行替代;壳单元节点被施加荷载压力、地层弹簧及约束支座,以模拟管片结构与围岩之间的力学行为。SPTSM提供了结构自动建模算法和壳单元节点荷载的自动计算算法,并通过调用Karamba3D有限元结构计算内核,实现盾构隧道结构的建模−计算一体化。将SPTSM应用于杭州某大直径盾构隧道工程76 m区间段,对比结构变形的计算和实际检测结果,验证SPTSM的合理性。SPTSM能自动建立精细的三维壳单元盾构隧道结构模型,并同时完成荷载压力、地层弹簧、线性−铰刚度以及约束支座的布置和设定。对比点云扫描的结构位移检测结果和SPTSM计算出的结构变形结果,SPTSM输出的结构变形云图属于合理范围,结合SPTSM输出的内力云图和荷载分布云图,SPTSM可以近似反映隧道结构局部位置的变形或位移趋势。综上,SPTSM可为盾构隧道的智能化结构设计提供有力支撑。

As compared to beam elements,3D shell elements can better simulate the mechanical behavior of tunnel structures influenced by soil.In order to promote the application of 3D tunnel structure calculation model with shell elements in large-diameter shield tunneling projects,this paper proposed a shell element-based parametric tunnel structure modeling(SPTSM)approach.SPTSM allowed for the quick generation of a tunnel structure model composed of shell elements based on the tunnel axis and cross-sectional radius.In the developed model,the common edges between adjacent rings were defined as linear hinges to simulate circumferential joint performance.The longitudinal joint stiffness of shield tunnel was processed by homogeneous ring method with introducing a discount factor.The load pressure,ground springs and restrained supports were applied to selected shell element nodes to simulate the mechanical behavior between the structure and surrounding soils.SPTSM also provide algorithms for automatic structural modeling and load calculation,and can integrate with the finite element structural calculation kernel of Karamba3D.To validate the effectiveness of SPTSM,it is applied to a 76 m interval section of a large-diameter shield tunneling project in Hangzhou.The calculation of structural deformation is compared to actual inspection results.SPTSM is shown to automatically generate a fine-grained 3D shell element model of the tunnel structure,and simultaneously complete the arrangement and settings of load pressure,ground spring,linear-hinged stiffness and restrained support.Comparing the structural displacement inspection results obtained from point cloud scanning and the results calculated by SPTSM,the results of SPTSM are within a reasonable range.It can approximately reflect the deformation or displacement trends at part of the tunnel structure.To sum up,SPTSM can provide strong support for intelligent structural design of shield tunnels.