Prediction of Construction Water Inflow of Karst Water-Rich Tunnel Without Drainage Tunnel

Abstract

AbstractThe construction of infrastructure in China faces substantial challenges due to the complex geological conditions and groundwater in karst areas, particularly in tunnel construction. The construction of the Maoping Port railway tunnel in the Three Gorges Hub area has been accompanied by the emergence of caves and faults. The excavation process for the tunnel has been found to expose caves and cavities, leading to sudden surges of water and mud, which can pose a risk. Hence, there is a pressing need to precisely forecast the water inflow in the karst region of Yangmuling Tunnel, in order to furnish guidance for the tunnel’s drainage and to avert surging water disasters in the absence of a relief hole. This study focuses on the water-rich karst issue in Yangmuling Tunnel. The research employed on-site hydraulic pressure monitoring and finite element numerical simulation to investigate the seepage and water influx properties of the tunnel without water relief hole. The outcomes of the study reveal that a low water pressure zone forms near the tunnel after excavation, and water pressure gradually increases outward. When the tunnel reaches the karst pipe, there is a sharp increase in water influx. Simultaneously, the low water pressure zone in the karst area sharply expands, resulting in an irregular shape. Excavation of the tunnel exposed the karst pipe, causing a rise in flow velocity in the karst zone towards the front of the tunnel face, but it subsequently declined rapidly. The alteration in flow velocity within the rock section surrounding the tunnel face was comparatively uniform.