本文依托济莱高铁宅科隧道工程,利用现场监测和FLAC3D数值模拟的方法,基于隧道应力传递路径的改变探究压力拱形成机制和分布范围,得出隧道纵截面压力拱形态特征图,引入位移完成率衡量围岩的开挖扰动程度,建立位移完成率和应力释放率的对应关系,得到最优初次支护时机.研究结果表明:在隧道开挖过程中,上部围岩中应力逐渐偏转,围岩荷载逐渐向四周传递,最终达到新的应力平衡状态,即在隧道四周产生形成封闭环状应力现象的压力拱;隧道仰拱靠近拱脚部位围岩产生应力集中,在1.8D(D为隧道截面宽度)范围内的围岩均参与成拱效应,承担隧道拱部上方的围岩荷载;对塑性区体积率进行计算与分析,认定70％～80％应力释放率较为缓慢,应作为最佳初期支护时间点;在开挖时隧道初期支护滞后于掌子面的距离宜控制在 4.3～7.6 m.
Research on the timing of initial tunnel support based on the development of pressure arch
Relying on the Jilai High-speed Railway Zhaike Tunnel project,using on-site monitoring and FLAC3D numerical simulation methods,this paper explores the formation mechanism and distribution range of pressure arch based on the change of tunnel stress transfer path,obtains the morphological characteristic map of tunnel longitudinal section pressure arch,introduces the displacement completion rate to measure the excavation disturbance degree of surrounding rock,establishes the correspondence between displacement completion rate and stress release rate,and obtains the optimal initial support time.The results show that the stress axis in the upper surrounding rock is gradually deflected during tunnel excavation,and the surrounding rock load is gradually transmitted to the surroundings,and finally a new stress equilibrium state is reached,that is,the pressure arch forming a closed annular stress phenomenon is generated around the tunnel.The surrounding rock near the arch foot of the tunnel upright arch produces stress concentration,and the surrounding rock within the range of 1.8D(D indicates the width of the tunnel section)participates in the arching effect,bearing the surrounding rock load above the tunnel arch.The volume rate of the plastic zone is calculated and analyzed,and it is determined that the stress release rate of 70％～80％is relatively slow,and it should be used as the best initial support time point.During excavation,the distance between the initial support of the tunnel and the face of the face should be controlled within 4.3～7.6 m.
万方数据
维普
