小净距公路隧道支护时机对围岩稳定性影响研究

Effect of supporting time on stability of small spacing roadway tunnel

随着西部高速公路的大规模建设,受地形和施工场地的限制,小净距隧道已越来越多地在工程实际中使用。由于小净距隧道施工工艺复杂,围岩变形和破坏机理也较为复杂,隧道的施工和支护时机对围岩和支护结构的稳定性影响很大。结合正在施工的沪-蓉-西高速公路漆树槽分岔隧道小净距段的施工特点,开展隧道在不同荷载释放比例下不同支护时机对围岩稳定性影响的研究。研究结果表明:支护越早,衬砌和锚杆承担的荷载越大,围岩的塑性变形和塑性区范围越小。及时施作二次衬砌,可以显著控制岩柱部位的变形,改善围岩的应力状态。研究成果将对同类条件下小净距隧道的施工和设计具有指导意义。

As large scale construction of highways in West China, more small spacing tunnels have been adopted due to the limitation of landscape. Because of the complexity of construction techniques, deformation and failure mechanisms of surrounding rock mass during excavation are complicated. Construction sequences and supporting time are important to the stability of rock mass and concrete lining. Effects of release proportion of the load and supporting time on stability of tunnel are studied based on construction characteristics of Qishucao Small Spacing Tunnel which belongs to Shanghai-Chengdu high-way. Numerical simulation results show that, as the lining constructed earlier, linings and anchors bear bigger load and the plastic deformation becomes smaller. Constructing the reinforced concrete lining in time can prominently control the deformation of the rock pillars and improve the stress condition of the surrounding rock mass. Achievements from the study can guide the design and construction of small spacing tunnel with similar conditions.