富水砂层影响下隧道围岩变形破坏机制的数值模拟研究

Numerical Simulation Study on the Deformation and Failure Mechanism of Tunnel Surrounding Rock under the Effect of Water-rich Sand Layer

为研究富水砂层影响下隧道围岩的变形破坏机制,文章以某城市地铁M2号线某区间隧道为研究背景,考虑了流砂层厚度、隔水层厚度、地下水位、隔水层粘聚力和内摩擦角五大类因素影响,设计了25种对比方案,开展了数值模拟对比研究,得到了不同因素对围岩变形破坏机制的影响规律及各因素影响敏感程度,给出了相应工程建议措施。结果表明:对于上覆富水砂层隧道,拱顶是围岩变形破坏的关键部位;随隔水层厚度、粘聚力及内摩擦角增大,顶部围岩变形量及塑性区面积不断减小,而随流砂层厚度增大或地下水位上升,顶部围岩变形量及塑性区面积则不断增大;隔水层厚度及粘聚力是影响此类地层条件隧道围岩变形破坏的显著性因素,一方面在隧道线路设计中应保证拱顶留设足够的隔水层安全厚度,另一方面可通过对隔水层进行注浆加固的方式,提高此类地层条件隧道围岩的稳定性。

In order to study the deformation and failure mechanism of tunnel surrounding rock under the effect of water-rich sand layer,taking a running tunnel of metro line M2 in certain city as the background,the effect of five factors of thickness of the sand layer,thickness of the water-resisting layer,underground water level and cohesion and frictional angle of water-resisting layer is considered.Twenty five comparison schemes are designed,a systemat⁃ic numerical simulation and comparison are carried out,the influence law of different factors on the deformation and failure mechanism of surrounding rock and the sensitivity degree of each factor are obtained,and the corresponding engineering measures are given as well.The results show that the crown is the key part of surrounding rock deforma⁃tion and failure in tunnels subjected to the effect of water-rich sand layer;the deformation and area of plastic zone of surrounding rock at crown decreases with the increase of the thicknesses of water-resisting layer,cohesion and in⁃ternal friction angle,while the deformation and area of plastic zone of surrounding rock at crown keeps increasing with the increase of thickness of the sand layer or underground water level;the thickness of the water-resisting layer and cohesion are the significant factors that affect the deformation and failure of surrounding rock under such condi⁃tions,adequate safety thickness of water-resisting layer at crown should be guaranteed as for the design of tunnel alignment and grouting reinforcement of water-resisting layer can be taken to improve the stability of tunnel sur⁃rounding rock.