基于离散-连续耦合方法的隧道压力拱特性研究

Research on tunnel pressure arch based on coupled discrete and continuous method

隧道压力拱问题一直是隧道工程研究的关键问题,目前常用的连续介质数值模拟方法对于隧道压力拱特性的微观研究有所欠缺,而擅长微观力学研究的离散元数值模拟方法对计算机存储空间和计算时间的要求太高。基于现有离散-连续耦合思路,通过力的传递实现离散-连续模型的耦合;研究了耦合算法中的平均应力计算方法、平均应力计算区域面积及耦合程序遍历颗粒方法;基于自行开发优化的离散-连续耦合程序,模拟了隧道开挖后的围岩受力特性,研究了隧道压力拱形成机理及压力拱特性;计算了埋深分别为10 m,14 m,18 m,22 m,26 m,30 m和34 m情况下的隧道开挖产生的压力拱应力集中等效区域,揭示了隧道压力拱随着隧道埋深的变化规律。研究结果表明,自行开发优化的离散-连续耦合程序能在保证计算精度的前提下,充分发挥离散元方法在微观力学研究方面的优势;隧道开挖后,开挖面周边范围出现层状压力环,但在拱顶和仰拱底附近区域的围岩压力环的环间接触力降低,围岩承载能力急剧降低,形成压力拱;随着隧道埋深的增加,隧道压力拱应力集中等效区域减小,隧道周边围岩的压力拱承载能力越来越大;但当隧道埋深达到一定界限后,隧道压力拱高度趋于稳定。

The pressure arch of a tunnel is a key problem in tunnel engineering.There is a lack of microscopic study of tunnel pressure arch characteristics as a continuous by a numerical simulation method.The discrete element method which is good at microscopic study requires a large computer storage space and a long calculation time.The discrete-continuous coupling model through the transmission of force is built based on the existing model.Calculation methods of mean stress,calculation area of mean stress and traversal particle method of coupling procedure are researched.The stress characteristics of surrounding rocks after tunnel excavation,the formation mechanism of a tunnel pressure arch and the tunnel pressure arch characteristics are studied based on the self-developed and optimized discrete-continuous coupling model.The equivalent area of stress concentration of a tunnel pressure arch generated by tunnel excavation is calculated under different buried depths of 10 m,14 m,18 m,22 m,26 m,30 m,34 m,which reveals the variation law of a tunnel pressure arch with tunnel burieddepth.The results show that,the self-developed and optimized discrete-continuous coupling model can not only ensure the calculation accuracy,but also give a full play to the advantages of discrete element method in microscopic study.Layered pressure rings appear near the excavation face after tunnel excavation,and the indirect contact force between the layered pressure rings of vault and invert bottom reduces,the bearing capacity of surrounding rock decreases.The equivalent area of stress concentration of a tunnel pressure arch is decreasing with the increase of tunnel buried depth,and the bearing capacity of a tunnel pressure arch is increasing.However,a tunnel pressure arch is stabile when the tunnel depth reaches a certain limit.