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.