小净距隧道群稳定性判定因素及施工顺序优化研究

小净距隧道群存在多种稳定性判定因素,为确定各判定因素之间的关联程度,以青岛地铁敦化路站为工程背景,结合修正Drucker-Prager模型,采用有限差分软件,得出6种不同施工方案下的最大拱顶沉降、塑性区体积、夹岩最大剪应力、锚杆最大轴力等判定指标值。以模糊灰色关联理论为基础,分析了各隧道群稳定性判定指标的主次顺序、隧道群施工最优方案。结果表明:锚杆最大轴力可作为对隧道群施工稳定性最主要的判定因素,拱顶最大沉降及塑性区体积可较为显著地反映隧道群施工稳定性,夹岩最大应力对稳定性影响较小;方案4及方案5可作为隧道群优选施工方案,等效应力分析验证了这2种方案的合理性。研究结果可供类似地铁工程的隧道稳定分析作参考。

Determinant Factors of Stability and Optimization of Construction Sequence in Tunnel Group with Small Clear Distance

Maximum vault settlement,plastic zone volume,maximum shear rock stress and maximum axial force of bolt etc.,are determinant factors which reflect the stability of tunnel group with small clear distance.To investigate into the correlation degree among these factors,we obtained the values of these determinant indexes by using finite difference software together with modified Drucker-Prager model.Dunhua road station of Qingdao metro is taken as engineering background.In line with fuzzy grey relational theory,the order of determinant factors and the optimum scheme of construction sequence are analyzed.Results reveal that maximum axial force of bolt can be taken as the primary determinant factor of tunnel group stability;while maximum vault settlement and plastic zone volume could also reflect the tunnel group stability significantly;maximum shear rock stress has the smallest influence on tunnel group stability.In the present study,scheme 4 and scheme 5 are concluded as the optimum construction sequences,and both are verified by equivalent stress analysis.