圆砾-泥岩复合地层土压/泥水双模盾构合理模式转换点选取

Selection of reasonable mode conversion point for earth pressure/slurry dual-mode shield in round graval-mudstone composite strata

为确保双模盾构在模式转换前后的安全、高效掘进,依托南宁地铁5号线五~新区间隧道工程,结合土压/泥水双模盾构模式转换原理,确立合理模式转换点选取原则及判据,建立考虑流固耦合效应的数值模型,深入分析掘进过程中掌子面变形量、渗流量的变化规律,建立施工安全、成本最优的多目标优化模型,通过等效变换得到模式转换点与地层交界面的距离,并结合工程实际转换点进行对比验证。研究结果表明:双模盾构模式转换点应选取在相对稳定的地层;掌子面变形量及渗流量在地层交界面附近差异明显;渗透系数差异3个数量级是影响土压/泥水双模盾构模式转换点的临界值;当渗透系数差异小于3个数量级时,模式转换点宜距离交界面8m;工程实际模式转换点与计算结果基本一致,可为土压/泥水双模盾构选取及模式转换提供参考和借鉴。

To ensure the safe and efficient tunneling of the EPB/Slurry dual-mode shield before and after mode conversion,the Wu-Xin section of Nanning Metro Line 5 was considered.The principle of rational mode conversion point selection and relevant criteria were proposed with consideration to the mode conversion procedures.A numerical model was established with consideration to the effect of fluid-structure coupling,and the evolution of the tunneling face deformation and seepage flow during the tunneling process was comprehensively analyzed.A multi-objective optimization model for construction safety and cost optimization was established and the mode conversion point was obtained through the equivalent transformation.The distances between the rational mode conversion point and the stratum interface were compared and verified to the actual conversion point of the project.The research results reveal that the mode conversion point of the dual-mode shield should be selected in a relatively stable stratum,and the deformation of the tunneling face and the seepage flow are significantly different near the stratum interface.The critical value is three orders of magnitude difference of the permeability coefficient for the selection of different mode conversion points.When the difference in the permeability coefficient is less than three orders of magnitude,the mode conversion point should be 8 m away from the interface.The actual mode conversion point of the project is basically the same as the result obtained by this study,which can provide a reference to future studies on the selection and mode conversion of the EPB/Slurry dual-mode shield.