基于壳体模型的隧道旋喷拱棚预支护下掌子面稳定性分析

Tunnel Face Stability with Jet Grouting Arch Shed Pre-support Based on Shell Model

为探究旋喷拱棚预支护下隧道掌子面稳定情况,将预支护拱棚简化成半无限长柱壳结构,引入Pasternak双参数地基模型,以此建立拱棚挠度方程,结合实际工程,将理论计算得到的拱棚挠度与数值计算结果进行对比,验证了双参数地基壳体模型的适用性。最后将在此理论模型下求解得到的地基反力作用于隧道掌子面上方,推导了掌子面稳定性公式,并探究在不同因素影响下隧道掌子面稳定性规律。结果表明:基于双参数地基下壳体理论的掌子面稳定分析模型由于考虑了预支护拱棚的整体加固效应以及下方岩土体的剪切变形作用,计算结果更加符合实际工程情况;围岩参数、施工因素、地层条件对隧道掌子面稳定有直接影响,不同参数影响程度不同,影响程度从大到小总体表现为:黏聚力、摩擦角、开挖高度、初始挠度、埋深,随着黏聚力增大、摩擦角增大、初始挠度减小、开挖高度减小、开挖进尺减小,掌子面稳定安全系数增大。当围岩较差时,纯粹短进尺不能保证掌子面稳定,需采取围岩加固或辅助措施;随着隧道埋深增大,掌子面稳定安全系数先线性减小后增加最后趋于稳定;减小开挖高度和控制初始挠度,对掌子面稳定性有利,此时再采用合理的开挖进尺对围岩稳定优势更明显。

To explore the tunnel face stability with jet grouting arch shed pre-support,the pre-support arch shed was simplified into the semi-infinite cylindrical shell structure.The Pasternak double-parameter foundation model was introduced to establish the arch shed deflection equation.Combined with the actual project,the theoretically calculated arch shed deflection was compared with the numerical calculation results.The applicability of double-parameter foundation shell model was verified.Finally,the ground reaction obtained with such theoretical model was used for the tunnel face.The tunnel face stability formula was deduced;and the tunnel face stability rule by using different factors was explored.The result indicates that the tunnel face stability analysis model based on the shell theory under the double-parameter foundation takes into account the overall reinforcement effect of the pre-supported arch shed and the shear deformation effect of underlying rock and soil.The calculation results are more in line with the actual engineering situation.The surrounding rock parameters,construction factors and stratum conditions have direct influences on the tunnel face stability.The influencing degrees of different parameters are different;the order from large to small is cohesion,friction angle,excavation height,initial deflection,buried depth.The cohesion increases;the friction angle increases;the initial deflection decreases;the excavation height decreases;the excavation footage decreases;and the tunnel face stability safety factor increases.When the surrounding rock is poor,the pure short footage cannot guarantee the tunnel face stability;and the surrounding rock reinforcement or auxiliary measures are needed.With the increase of tunnel depth,the tunnel face stability safety factor first decreases linearly;then increases;and finally tends to be stable.Reducing the excavation height and controlling the initial deflection are beneficial to the tunnel face stability.Meanwhile the reasonable excavation footage is more obvious for the surrounding rock stability.