干燥粉细砂隧道超前预加固与施工研究

 大西铁路客运专线上白隧道穿越干燥粉细砂地层，施工难度及风险很大。通过现场密排小导管和深层咬合桩预加固效果对比试验，得出深层咬合桩预加固可有效控制开挖中的流砂及涌砂。同时，对粉细砂地层及深层咬合桩固结体进行直剪试验、三轴试验及侧限压缩试验等室内试验，得到地层及固结体的各项物理力学指标，且认为三轴试验所得各指标更为真实、可靠。在此基础上，对干燥粉细砂地层隧道开挖方法进行数值模拟和现场试验测试，提出合理的施工方法建议。研究结果为上白隧道施工提供技术支持，也可供类似工程参考。

PRE-REINFORCEMENT AND CONSTRUCTION OF TUNNEL IN DRY FINE SAND LAYERS

Shangbai large cross-section tunnel in Datong-Xi?an Passenger Dedicated Lines passes through dry fine sand layers. Its construction technologies are difficult and risky. Through the comparative field experiments of close-packed small pipe and deep secant pile of pre-reinforcement，it is found that the deep secant pile pre-reinforcement scheme can effectively control the quick sand and sand gushing during the tunnel excavation. Meanwhile the physico-mechanical parameters of the fine sand layers and consolidation body are obtained by deep secant pile test through laboratory tests，including direct shear tests，triaxial tests and unconfined compression tests. On this basis，through the numerical simulation and field test of tunnel excavation method in dry fine sand layers，the reasonable construction scheme is proposed. The results can provide technical support for Shangbai tunnel construction and reference for similar projects.