高速公路分岔隧道施工过程稳定性分析与监测研究

分岔隧道连拱段至小净距段的过渡处，中墙由钢筋混凝土变为原岩，施工过程十分复杂。采用三维数值方法和施工现场监测相结合的方法研究了分岔隧道施工过程中的稳定性，数值模拟了无支护开挖和施加锚喷、二次衬砌支护后隧道的受力及稳定性。计算结果表明，支护后稳定性显著增强，与现场监测结果对比一致，隧道整体稳定性较好，但是中墙产生较大的应力集中，靠近连拱段的小净距段稳定性较差；锚喷、衬砌支护对于减缓围岩应力集中程度，减少塑性区、降低位移量有明显效果。最后在保证隧道安全的基础上提出了隧道支护的优化措施。

Stability and Monitoring on Construction Process of Expressway Forked Tunnel

The construction process of forked tunnel is very complex because tunnel transition includes double-arch section, small clear spacing section and middle wall transfer from reinforced concrete to rock. The stability of forked tunnel in construction process was simulated using FLAC3D and monitored in-situ.Tnnnel stability and its stress distribution with bolt-shotcrete and lining support or without support were analyzed by numerical simulation. Numerical result shows that tunnel stability is enhanced by support and accords with in-situ monitoring. Numerical and monitoring results show that, tunnel is stable but the stress in middle wall is largest, the tunnel small clear spacing section near double-arch section is unsafe; the bolt-shotcrete and lining support have good effect on relaxing surrounding rock stress distribution, reducing plastic zones and displacement.Finally, the optimum reinforcement measure was proposed to support forked tunnel.