蒙华铁路风积沙地层隧道围岩稳定性及预加固效果试验研究

为了解风积沙地层隧道失稳变形特征和预加固控制效果，以蒙华铁路风积沙地层段为依托，通过室内物理力学试验得到风积沙的基本性质和参数，并利用数值模拟对隧道最大主应力和塑性区变化规律展开分析，然后建立模型试验对不同预加固方式在风积沙地层隧道中的效果进行研究。研究结果表明： 1）风积沙抗剪切能力在含水率为7%~14%时可达到极值，此时更利于隧道围岩的稳定性； 2）隧道失稳具有突发性，主要会经历“掌子面局部破坏—拱顶持续塌方—大体积失稳”3个基本过程； 3）未采用预加固措施的情况下，开挖面前方监测断面拱顶围岩内部位移值及变形速度最大，采用水平旋喷桩与钢管组合加固后可分别降低81.1%和98.3%； 4）水平旋喷桩与钢管的组合对于开挖面前方拱顶的围岩应力控制效果最好，水平旋喷桩的加固控制范围小于水平旋喷桩与钢管的组合。

Experimental Study of Surrounding Rock Stability and Pre reinforcement Effect of Aeolian Sand Tunnel on Menghua Railway

The study of the instability deformation characteristics and pre reinforcement control effect of aeolian sand tunnel is of great significance. Hence, the basic properties and parameters of aeolian sand formation of Menghua Railway are obtained by laboratory physico mechanical experiment. And then the variation laws of maximum principal stress and plastic zone of the tunnel are analyzed by numerical simulation. Finally, the effects of different pre reinforcement methods in aeolian sand tunnels are studied by model experiment. The experimental results show that: (1) The anti shear ability of aeolian sand can reach the extreme value when the water content is about 7%-14%, which is more conducive to the stability of tunnel surrounding rock. (2) The instability of the tunnel is sudden, which will mainly experience 3 basic processes, i.e. partial destruction of the tunnel face, crown collapse continuously, and large volume of instability. (3) The internal displacement and deformation velocity of the surrounding rock of the crown ahead of excavation face without pregrouting are the highest, which could be reduced by 81.1% and 98.3% respectively after the combined reinforcement of horizontal rotary jet grouting piles and steel pipe. (4) The combination of horizontal rotary jet grouting pile and steel pipe has the best effect on the surrounding rock stress control of crown ahead of the excavation face; and the reinforcement control range of horizontal rotary jet grouting pile is smaller than the combination of horizontal rotary jet grouting pile and steel pipe.