浅埋偏压隧道围岩破坏模式及规律研究

Study on the Failure Mode and Regularity of Surrounding Rock of Shallow-buried Tunnel under Unsymmetrical Pressure

破裂角在一定程度上可作为独立的指标描述无特殊地质构造的浅埋隧道破裂模式。针对现有破裂角公式中未综合考虑隧道几何特性和地形特性的不足,选取影响隧道稳定性的覆跨比、扁平率及偏压角3个因素,以太沙基破裂角公式和《铁路隧道设计规范》中破裂角公式为理论基础,推导新的破裂角公式。基于推导的破裂角公式,分析上述3个因素对破裂角的影响规律,并建立隧道破坏模式与围岩压力以及破裂角之间的关系。结果表明:本文推导的破裂角公式具有一定的适用性,对于浅埋隧道而言,其破裂角随着覆跨比和扁平率的减小而增加;对于偏压隧道而言,深埋侧的破裂角小于浅埋侧,且深埋侧的破裂角随着偏压角增大而减小,浅埋侧则相反;随着破裂角的增大,对应的隧道破坏模式分别为冒落松动模式、滑移破裂模式和错台塌陷模式,围岩压力的计算模型分别符合普氏塌落拱模型、一般浅埋隧道模型和太沙基散粒体模型。

The rupture angle can be used as an independent index to describe,to a certain extent,the failure mode of shallow-buried tunnel without special geological structure.In view of the shortcomings of the existing rupture angle formulas that do not take into account the tunnel properties of geometric and terrain comprehensively,three factors that affect the stability of the tunnel are selected,namely thickness-span ratio,flat ratio and the bias angle.Then,based on the rupture angle formulas of Terzaghi and the relevant specification,a new rupture angle formula is derived.Based on the deduced rupture angle formulas,the influences of the above three factors on the rupture angle are analyzed,and the relationships among tunnel failure mode,surrounding rock pressure and rupture angle are established.The results show that the formulas of rupture angle deduced in this paper have certain applicability.For shallow-buried tunnels,the rupture angle increases as the thickness-span ratio and flat ratio decrease.For biased tunnels,the rupture angle on the deep-buried side is smaller than that on the shallow-buried side,and the rupture angle of the deep-buried side decreases with the increase of the bias angle,while the shallow-buried side is just the opposite.As the rupture angle increases,the corresponding tunnel failure modes are falling-loosening mode,slipping-crack mode,and stagger-collapse mode respectively,and the calculation models of surrounding rock pressure are in accordance with the Protodyakonov’s collapsed arch model,the general shallow-buried tunnel model and the Terzaghi granular model.