Multiple Water and Sand Leakage Model Tests for Shield Tunnel

Water and sand leakage in shield tunnels has become more of a research interest in recent years. On the other hand, accidents involving underground engineering can take many forms and occur often. These accidents pose a risk to people's lives as well as their property, and it is imperative that study on underground engineering catastrophes be conducted without delay. At the moment, there is a deficiency in the number of systematic research and theoretical framework that pertains to the evolution mechanism of tunnel leakage and erosion disaster. In this paper, a technique of indoor model test for disaster and erosion in shield tunnels is utilized in this study to investigate the process of crater, water, and sand leakage evolution in shield tunnels. The change in water pressure at the leaking joint is inversely proportional to the magnitude of the water input rate, and the change in soil pressure is inversely proportional to the distance from the leakage joint. Both changes occurred in the same direction. Notably, the soil's initial effective stress was also considered to maintain compatibility with actual engineering works. The preliminary findings suggested that soil-effective stress may cause erosion resulting to the soil arching effect. Tests with one and two leakage spots were carried out using this foundation. Compared to the scenario where two leakage sites are opened simultaneously, it was discovered that opening the two leakage points one after the other might result in a more extensive erosion area of superposition. The double leakage points test results indicate that the point where leakage occurs first causes another leakage point because the erosion area created when two leakage points are opened successively will be larger than the erosion area created when two leakage points are opened simultaneously. When two leakage points under a tunnel are close to each other, the width and depth of the soil erosion groove under the tunnel caused by the two leakage points leaking one after another are significantly larger than those caused by two leakage points leaking simultaneously and are also substantially larger than a single leakage point. After a leakage disaster occurs in the tunnel, the water and soil pressure near the leakage point will continue to decrease. The closer to the leakage point, the greater the reduction. Until the leakage erosion converges, the water and soil pressure will tend to stabilize.