浅埋偏压小净距隧道的力学特性及方案比选研究

浅埋偏压小净距隧道的围岩位移及力学性能与一般隧道有显著的区别,施工中稍有不慎将发生塌方事故。该文结合重庆南山隧道出口端浅埋偏压段工程实际及现场监测数据,利用ANSYS建立浅埋偏压隧道二维有限元模型及施工监测数据对各工况围岩位移、应力场及锚杆轴力进行对比分析,研究了其施工力学特性。结果表明:两洞开挖顺序不同,最终位移和应力量值存在较大差异,通过增加深埋侧隧道锚杆长度,有效地改善了围岩的受力特性,提高了隧道施工的安全性。分析结果可为不同环境隧道施工选择合理开挖方案提供参考,具有重要意义。

Study on Mechanical Characteristics and Scheme Comparison of the Closely Spaced Tunnels with Shallow-Buried and Unsymmetrical Pressure

There are obvious differences between the surrounding rocks displacement and mechanical characteristics of closely spaced tunnels with shallow-buried and unsymmetrical pressure and that of general tunnels.Collapse accident may occur in construction if not handled with care.Based on the actual condition and monitored data of the shallow-buried and unsymmetrical pressure of the tunnel exit in Nanshan Mountain of Chongqing and with the application of ANSYS to set up the two-dimensional finite element model of shallow-buried tunnel with unsymmetrical pressure and the construction monitored data,the surrounding rock displacement,stress field and bolt axial force are compared and analyzed with construction mechanical characteristics studied.The results show that different excavation sequence of two holes will result in great distinction of eventual displacement and stress values.The stress characteristics of surrounding rocks can be effectively improved by increasing the bolt length of deep buried tunnel side and the safety of tunnel construction can be also enhanced.It is of significance to provide some references for different tunnel excavations to choose a reasonable excavation plan.