Innovative Sealing Approaches for Karst Flowing Groundwater: Numerical Analysis of Secondary Grouting Mechanism After Grout‐Filled Bag Sealed

Groundwater pollution in karst regions poses a serious threat to the ecological environment and public health. Effective sealing of karst conduits with flowing water still remains a significant engineering challenge at present. This study introduces an innovative sealing technique combining grout‐filled bag plugging with secondary grouting. Mechanism of grout filling and diffusion during secondary grouting in flowing water at the gap between grout‐filled bag and bedrock boundary of the karst conduit was analyzed through computational fluid dynamics simulations. Effect of water flow velocities, grouting rates, and grout‐filled bag dimensions was investigated. Our results indicate that water flow velocity is a pivotal factor in secondary grout sealing efficacy. Grouting effectiveness is significantly impacted when water flow velocity exceeds 0.1 m/s. However, increasing grouting speed can counteract this effect. When grouting speed exceeds water flow velocity, the grout filling ratio increases. Grout filling ratio reaches its maximum when gap sizes range from 0.7 to 0.8 m. Under identical grout flow velocities, the differences in viscosity and density between water and grout create uneven pressure distribution. This causes water to compress and displace the injected grout, reducing the grout filling ratio within the gap. Notably, when grouting speed surpasses or equals the flowing water rate, a dynamic sealing mass forms upstream of the bag, providing additional pathways for grout migration and significantly bolstering the sealing effect. These insights are instrumental for the construction design of large leakage conduit sealing, especially within karst regions.