Comparative Experimental Study on Deformation of Transparent Soil Induced by Construction of Quasi-rectangular and Circular Tunnels at Different Buried Depths
The quasi-rectangular tunnel has gradually gained popularized in engineering because of its space advantages. However, there is a lack of in-depth research on the differences between quasi-rectangular and circular tunnels in the surrounding soil layer changes, which are closely related to the buried depth of tunnels. The quasi-rectangular and circular tunnel excavation devices were independently designed and assembled, and transparent soil was used to simulate the surrounding soil layers. Particle image velocimetry (PIV) was used to accurately measure the deformation of the soil layer, and the law of soil deformation induced by the dynamic construction of quasi-rectangular and circular tunnels at different buried depths was analyzed. Experimental comparison results elucidate that the sliding surfaces of the soil deformation induced by the two types of tunnels are basically the same, which roughly conforms to the vertical sliding surface assumption of Terzaghi’s theory. The sliding angle (θ) is approximately equal to 45°+φ/2. The vertical deformation of the overlying soil layer of the circular tunnel always maintains a “V” shaped normal distribution at different buried depths, indicating the presence of a maximum value. The vertical deformation of the overlying soil layer of the quasi-rectangular tunnel changes from a “V” shape to a “W” shape as the depth of the formation increases, indicating the existence of multiple maximum settlements. This suggests that rectangular tunnels result in more uniform ground deformations compared to circular tunnels. Under the same burial depth, the maximum surface settlement induced by the excavation of similar rectangular tunnels is smaller than that of circular tunnels, especially in shallow burial conditions. The difference between both two gradually decreases with the increase of buried depth. These findings can serve as references for the design and selection of construction schemes.