基于现场实测数据统计的隧道围岩全过程变形规律及稳定性判据确定

Whole-process deformation laws and determination of stability criterion of surrounding rock of tunnels based on statistics of field measured data

隧道围岩全过程变形是认识支护与围岩相互作用演化机制的基本前提,也是围岩稳定性评价和支护设计的重要依据。在对40座隧道与地下工程围岩全过程变形进行收集和整理的基础上,系统分析了隧道围岩全过程变形及其关键节点、围岩变形速率与变形加速度分布规律与影响因素。研究表明:隧道围岩超前变形量和基本稳定变形量随施工进度呈总体增大趋势,随开挖半径呈减小趋势,而相应的位移释放率则无明显相关关系;随着围岩级别的增大,超前变形量与基本稳定变形量增大,而相应的位移释放率则反而减小;通过改进Hoek公式对深、浅埋条件下围岩全过程变形进行拟合,拟合优度在0.95以上,可为围岩损失位移的求解提供依据;隧道围岩变形速率随时间发展趋势为先增大后减小,而变形加速度则表现出"正弦曲线"特征,二者随隧道半径和施工速率变化显著。根据分析结果,指出对于不良地质条件下的大断面隧道,围岩变形速率小而变形持续时间长,此时围岩稳定性的判断应以变形加速度作为主要指标,并进一步给出了变形加速度阈值的确定方法。

Deformation of the surrounding rock during the whole excavation process is the basic premise to understand the evolution mechanism of interaction between the supports and the surrounding rock,which is also an important reference for stability evaluation of the surrounding rock and design of the supports.On the basis of collecting the deformation of the surrounding rock during the whole excavation process of 40 tunnels and underground projects,the whole process deformation and its key nodes,the distribution laws of deformation rate and deformation acceleration of the surrounding rock and the influencing factors are systematically analyzed.The results show that the advance deformation and basically stable deformation of the surrounding rock increase with the construction speed and decrease with the excavation radius,while the corresponding displacement release rates have no obvious correlation.With the increase of the surrounding rock,the advance deformation and basic stable deformation increase,and the corresponding displacement release rate decreases instead.By improving the Hoek’s formula,the whole-process deformation of the surrounding rock is fitted,and the goodness of fitting is above 0.95,which can provide a basis for the solution of loss displacement.The deformation rate of the surrounding rock first increases and then decreases with time,while the deformation acceleration shows the characteristics of"sinusoidal curve",both of which change significantly with tunnel radius and construction speed.According to the analysis results,it is pointed out that the deformation rate of the surrounding rock is small and the deformation duration is long for the large-section tunnels under unfavorable geological conditions,and the deformation acceleration should be taken as the main index to judge the stability of the surrounding rock.Furthermore,the determination method for deformation acceleration threshold is given.