中文摘要：

为了及时预防公路隧道穿越水平岩层施工过程中极易出现的平拱、拱顶离层破坏、拱顶弯折内鼓等危害现象，确定合理的支护方案，结合广元一巴中高速公路某穿越水平岩层隧道，根据现场跟踪调查和试验，在对围岩岩性、物理力学性质、地层结构和变形破坏类型等进行分析的基础上，对原洞身围岩质量分级结果进行了调整，对原支护设计方案进行了优化，并利用数值模拟方法验证了其合理性。同时，施工后拱顶下沉及周边收敛监测结果显示，围岩变形完全满足要求，进一步证明了支护优化设计合理，效果明显。

英文摘要：

In order to take precautions against and deal with the hazard appearance of flat arch, separation layer destruction and flexing and inside-drum of arch crown, etc. , and to determine rational supporting project, combined with the site tracing survey and examination to the horizontal bedded surrounding rock tunnel of Guangyuan-Bazhong Expressway, the original surrounding rock grade was adjusted and former support design project was optimized under the foundation of analyzing the surrounding rock lithologic characters, physical and mechanical properties, stratum structures and types of deformations and destructions. Using numerical simulation method, authors analyzed the rationality of former support design project. At the same time, the monitored results of arch crown subsidence and peripheral convergence show that the distortions are all satisfactory. It is proved once again that the support optimum design is appropriate, and the effect of optimum support is obvious.