局部膨胀土作用下隧道稳定性试验研究

膨胀土在中国分布极为广泛，目前相应的研究主要集中于工程监测以及数值模拟，容易出现代表性数据缺乏，结果与实际差别较大等不足。本文通过自主研发的膨胀土隧道设备进行模型试验，对底部膨胀土和左侧膨胀土对隧道稳定性的影响进行研究，探究膨胀作用下隧道的力学响应特征以及围岩变形分布规律，得出如下结论:底部和一侧膨胀作用结束后隧道的环向压力分别达到97.23和37.75 kPa，位于膨胀土对侧位置处的压力几乎为0 kPa，呈现时间正相关和距离负相关现象，底部分布膨胀土情况下扰动范围较大，而一侧分布破坏较为集中；膨胀作用对于隧道的影响是荷载和应变缓冲的共同作用下的非线性相关变化，在膨胀时间为1/5时将出现首次应变缓冲，环向压力增幅迅速减小；当隧道底部分布均匀膨胀土层时可以将膨胀土层看作受弯结构研究隧道的力学特征；不同部位膨胀土作用下的围岩变形将产生剧烈剪切破坏带，根据膨胀土分布位置分别出现单边剪切和双边剪切。

Experimental Study on Tunnel Stability Under the Action of Local Expansive Soil

Expansive soils are widely distributed in China. The corresponding research mainly focuses on engineering monitoring and numerical simulation, and it is easy to cause problems such as lack of representative data and large differences between the results and the actual situation. Through the self-developed expansive soil tunnel equipment, this paper conducts model tests, studies the influence of expansive soil at the bottom and expansive soil at the left on the tunnel stability, explores the mechanical response characteristics of the tunnel under the action of expansion and the deformation distribution law of surrounding rock, and draws the following conclusions: After the end of expansion at the bottom and one side, the circumferential pressure of the tunnel reaches 97.23 kPa and 37.75 kPa, respectively. And the pressure at the opposite side of the expansive soil is almost 0 kPa. This shows a positive correlation with time and a negative correlation with distance. The effect of expansion on the tunnel is a non-linear correlation change under the joint action of load and strain buffer. The first strain buffer will appear after 1/5 of the expansion time, and the increase of circumferential pressure will decrease rapidly. When the uniform expansive soil layer occurs, the expansive soil layer can be regarded as a flexural structure to research the mechanical characteristics of the tunnel. The surrounding rock deformation under the action of expansive soil at different positions will produce severe shear bands, and unilateral shear and bilateral shear will appear respectively according to the distribution position of expansive soil.