中文摘要：

机械预切槽法结合了盾构的盾壳保护开挖理念和新奥法处理复杂地层自由灵活的理念，任预筑拱的保护下可以进行下部隧道大断面开挖。这种方法在土砂等强度极低场合以及近接施工方面具有显著的优势，是一种很有发展潜力的隧道施工方法。文章结合当前预切槽法试验中槽内混凝土喷灌网难这一难题，在资料调研及计算分析基础上，论述了预切槽法对槽内混凝土强度及其它性能的特殊要求，计算得出双线大断面黄土隧道切槽内混凝土8h抗压强度应达到12MPa，研究提出要解决槽内混凝土难以喷灌的问题，需要改进传统的喷混凝土设备，同时要优化混凝土配比并进行切槽混凝土的室内试验和现场取芯试验对比。

英文摘要：

Using the concept of protection by shield shell and flexibility of NATM for complex geology, large-sec- tion excavation is possible under the protection of a pre-built arch using the mechanical pre-cutting method, which has obvious advantages in low-strength sand and soil strata approaching construction. Regarding the problem of dif- ficult spraying and pouring of concrete in the slot, such special requirements as concrete strength and other proper- ties are discussed based on an investigation and calculation analysis. It is concluded that the compressive strength of concrete in the slot after 8 hours should reach 12 MPa for a double-track loess tunnel with a large section; the tra- ditional concrete spraying equipment needs to be improved, and the mixing ratio of concrete should be optimized and an indoor experiment for concrete in the slot should be compared with the coring test at the site.