全风化红砂岩地层隧道掌子面变形特征及控制技术研究

为解决全风化红砂岩地层隧道在开挖过程中出现的掌子面失稳问题，以浩吉铁路阳城隧道为工程依托，利用现场调研、室内试验以及数值模拟等多种研究方法，对全风化红砂岩地层隧道掌子面的变形特征及控制技术进行系统研究。结果表明： 1）掌子面挤出位移主要集中在掌子面高度3~10 m的位置，掌子面最大挤出位移出现在上台阶和中台阶交界位置。2）拱顶沉降主要发生在已开挖段和掌子面前方约1倍洞径处，其预变形量占总变形量的比值均在40%以上，最大达到78.33%。3）掌子面前方核心土挤出变形曲线的变化趋势从快速减小到缓慢减小，直至减小为零，大致将其分为强影响区、弱影响区和无影响区3个区间，影响范围为5.8~19.2 m。4）阳城隧道采用超前水平旋喷桩和三台阶预留核心土法可以较为有效地控制掌子面的挤出变形，实际施工中，建议在采取降水措施的情况下将2种控制措施配合使用。

Deformation Characteristics of Tunnel Face and Corresponding Control Measures in Fully Weathered Red Sandstone Stratum

The failure of tunnel face stability often occurs during tunneling in fully weathered red sandstone. Hence, a case study is conducted on the Yangcheng tunnel of Haolebaoji Ji′an railway. Then a systematic study on the deformation characteristics and control measures of tunnel face in fully weathered red sandstone stratum is conducted using various research methods such as field investigation, laboratory test, and numerical simulation. Research results reveal the following: (1) The extrusion displacement of tunnel face is mainly concentrated in the position of face height of 3~10 m, and the maximum extrusion displacement of tunnel face appears at the junction of upper and middle benches. (2) The crown settlement mainly occurs at about one time of the tunnel diameter in front of the excavated section and the tunnel face, which accounts for more than 40% in total deformation (with a maximum reaching 78.33%). (3) The change in the core soil extrusion curve in front of the tunnel face decreases rapidly first and then becomes slowly, which can be roughly divided into strong influence, weak influence, and no influence zones. The range of influence is 5.8~19.2 m. (4) The extrusion deformation of the tunnel face of Yangcheng tunnel can be effectively controlled by adopting advance horizontal jet grouting pile and three bench reserved core soil method. The two proposed methods can be applied under the premise of dewatering.