高速铁路黄土隧道群修建技术与应用——张茅大断面黄土隧道修建技术成果总结

Construction Technology and Application of Railway Tunnel Group in Loess: A Case Study of Zhangmao Large Cross-sectional Tunnel

针对以张茅隧道为代表的郑西高铁大断面黄土隧道建设中的一系列技术难题,通过大规模现场试验和理论分析,对大断面黄土隧道修建成套技术进行了研究。研究结果表明：系统锚杆轴力较小,不超过12 k N,且拱部受压,边墙受拉;型钢、格栅钢架拱部平均应力分别为132 MPa和86 MPa,格栅应力相对均匀;新老黄土预留变形量建议取值分别为25~28 cm和10~15 cm;深浅埋分界深度为40~60 m;竖向初期支护与围岩接触压力实测较理论计算值小;浅、深埋隧道二次衬砌平均荷载分担比例为50%和10%;激振试验表明激振230万次后仰拱填充面的沉降稳定值≤0.5 mm,隧底饱和黄土未发现软化、泥化现象;大断面黄土隧道一般地段宜采用三台阶法开挖;砂质黄土浅埋下穿高速公路采用双侧壁导坑法施工时,地表沉降可控制在5 cm以内;可采用水泥土挤密桩消除隧道基础黄土湿陷性;饱和黄土隧道以排为主的方案可行。

During the construction of Zhangmao large cross-sectional tunnel in loess on Zhengzhou-Xi＇an high-speed railway,various technical problems were met. In this paper,the construction technologies for large cross-sectional tunnel in loess are proposed on the basis of field tests and theoretical analysis. The results show that： 1） The axial force of the anchor bolt is smaller than 12 k N in the support system. The tunnel arch is under compression and the side wall is under tension. 2） The average stress on the shaped-steel is 132 MPa,and that on the girder is 86 MPa. The stress imposed on the girder is even. 3） The deformation allowance of the surrounding rock Grade V is 25 ~ 28 cm,and that for Grade IV is 10 ~ 15 cm. 4） The critical value between deep and shallow overburden is 40 ~ 60 m. 5） The measured contact stress between the primary support and surrounding rock is smaller than theoretical calculations. 6） The secondary lining of shallow tunnel shares 50% of load,and the secondary lining of deep tunnel shares 10% of load. 7） The vibration excitation test shows that the value of invert settlement is smaller than 0.5 mm after 2,300,000 times of excitation,and the saturated loess beneath the tunnel floor never goes soften or argillized. 8） The three-step excavation method is preferred for large-diameter tunnel construction in loess. 9） The ground surface settlement can be controlled within 5 cm when double side drift method is used in construction of shallow sandy loess tunnel undercrossing highway. 10） The cement-soil compaction piles can be used to eliminate the collapsibility of loess. 11） The drainage scheme of ＂drainage taks the first place＂is suitable for tunnel construction in saturated loess.