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通过对北京和深圳地铁、厦门海底隧道、机场路等工程的现场监测结果的综合分析表明,浅埋暗挖隧道的受力机制与山岭隧道有较大不同,上覆地层变形体现出明显的整体下沉趋势,且带来的地层开裂、破坏更具突发性和破坏性。针对这种特征,对工程中地层滑动破裂角采用一种新的模型进行推导,其结果显示,地层滑裂角比传统结果大约15°,即滑裂面更陡峭、接近竖直方向,且该滑裂角是围岩参数、应力场、覆跨比、断面矢跨比的函数,一定程度上体现了围岩变形破坏类似的具几何效应,即浅埋暗挖隧道上覆地层的整体下沉、塌陷,突发性冒顶等特征,是由围岩的力学特性和几何特性共同作用的结果。另外,隧道结构下部土体的扰动、损伤、软化等,极易造成下部地层沉降和承载力的丧失,随之而来的即是隧道结构的整体下沉、支护效果恶化以及进一步的上覆地层整体沉降加剧。相应的采用理想弹塑性模型、修正剑桥模型的数值模拟分析,能部分反映这种上覆地层整体下沉的特征。研究结果还表明:对浅埋暗挖隧道围岩受力变形机制、本构关系的研究急需加强。
Through the comprehensive analysis of on-site monitoring results of Beijing-Shenzhen Subway, Xiamen Subsea Tunnel and Airport Road, it shows that the stress mechanism of shallow-buried tunnel is quite different from that of mountain tunnel, and the deformation of overlying strata shows obvious overall Sinking trend, and the resulting formation cracking, destruction more sudden and destructive. Aiming at this feature, a new model is used to deduce the slip rupture angle of the formation. The results show that the slip angle of the formation is about 15 °, which is steeper than the traditional result, that is, the slip plane is steeper and close to the vertical direction The slip-crack angle is a function of surrounding rock parameters, stress field, span ratio and cross-sectional aspect-span ratio, which reflects the similar geometric effects of deformation and failure of surrounding rock to a certain extent. That is, the overall subsidence of overburden , Collapse, sudden fall and other characteristics, is the result of the mechanical and geometrical characteristics of the surrounding rock. In addition, the disturbance, damage, softening and so on of the soil in the lower part of the tunnel structure can easily lead to the subsidence of the lower strata and the loss of the bearing capacity. The consequent is the overall sinking of the tunnel structure, the deterioration of the supporting effect and the further overlying Deposition of the whole formation intensified. Correspondingly, the ideal elastic-plastic model is adopted and the numerical simulation analysis of the modified Cambridge model can partly reflect the characteristics of the overall overburden subsidence. The results also show that the research on the constitutive relationship urgently needs to be strengthened for the mechanics and deformation of the surrounding rock of shallow-buried tunnel.