Study of Water–Sand Inrush through a Vertical Karst Conduit Uncovered through Tunnel Excavation

The existence of karst compromises the safety underground engineering, especially during tunnel excavations. Karst conduits are uncovered through excavations, which may lead to a water–sand inrush disaster. Taking vertical conduit as an example, process could be viewed being similar whereby mixture flows discharge opening storage bin. In this study, based on force analysis non-aqueous sand body above conduit, limiting diameter under equilibrium was obtained. Considering effect water aqueous bodies, criterion established. We aimed study migration and in order obtain distribution pressure near explore relationship between size, pressure, flow rate; therefore, simulated testing system for analyzing developed. When chamber close critical head inrush, exhibited pattern instability—migration—deposition—stability. exceeded increased first then stabilized over time. With increase set values steady gradually. opened suddenly, actual decreased significantly, due flowing out supply lagging behind. stabilization flow, gradually tended towards stability, but it still lower than initial pressure. opened, monitored by pore gauges all clearly decreased. became stable. distance sensor These test results significant further studies formation mechanisms conduits.