| The underground water inrush or gushing have been caused seriously because of serious karst pipelines,caves and cracks in recent years.The inrush or gushing of large-flow karst pipeline is highly catastrophic,and it is very difficult to block and control worldwidely.The plugging of large-flow karst pipelines flow has become a major scientific key problem in the construction of underground engineering,and it is also urgent to be solved.In this paper,combining with theoretical analysis,laboratory experiments,numerical analysis and field test,the flow control and grouting blocking mechanism of large-flow karst pipeline gushing water were studied,and a complete set of treatment method of large-flow karst pipeline gushing water was proposed.These research results have been successfully applied to the water gushing treatment of the largest sunk karst limestone mine in China.The main research contents and achievements are as follows:(1)Through the analysis of water gushing characteristics of karst pipelines,the karst pipeline gushing water model was proposed.Based on the water hammer phenomenon,hydraulic mechanism and the large-flow unsteady flow equation,the flow control and flow-rate reduction model for pipeline gushing water has been established.The pressure formula for flow control and flow-rate reduction was proposed by deducing the gushing movement equation.The mechanism of flow control and flow-rate reduction was revealed,and the construction control methods of low control and flow-rate reduction for karst pipeline water gushing has been formed.(2)The indoor flow control and rate reduction test of pipeline type gushing water was carried out.The variation law between fluid flow velocity,pressure and flow control of pipeline orifice was obtained.Experiment results showed that the relationship between when the opening value and flow velocity existed v=0.1743e2 5543d,this was the determined exponential equation in this study.It indicated that the flow control technology decreased flow velocity obviously.Combined with Comsol numerical analysis,the process simulation analysis of the flow reduction and velocity reduction for large-flow pipeline was carried out,and the effectiveness of the flow reduction and velocity reduction has been further verified.(3)The physico-chemical properties of cement slurry and cement-based quick-setting slurry were analyzed systematically.The diffusion equations of viscosity characteristics for Newtonian and Bingham typical slurries were deduced based on time-varying viscosities.The analytical expressions of grouting volume and diffusion sensitive parameters were established during the one-dimensional diffusion process in pipelines.The grouting amounts of the one-dimensional pipeline were studied with different grouting parameters.The various numerical computation methods of slurry-water two-phase flow considering the time-varying viscosity for typical slurry were studied.The experimental systems for pipeline-type hydrodynamic grouting diffusion simulation were developed,and the grouting plugging mechanisms of large-flow karst pipeline gushing were revealed.(4)Considering the information of drilling,connection test and pumping test,and the dividing basis of runoff fields for sunk karst depression mine was proposed.The typical voxel principle assignment for each calculation zone was used,and the analysis methods of groundwater seepage field were established in the karst sunk mine.In combination with numerical simulation analysis of the karst sunk mine runoff of Guangxi China Resources Hejing Cement area,the groundwater seepage field of karst mines in different periods were studied.The distribution and law of groundwater head,streamline and flow velocity were determined.The feasibility of non-continuous curtain grouting plugging for the mine runoff zones was verified.The low field variation characteristics of groundwater were compared and analyzed before and after the implementation of discontinuous curtains in the mining area.The influence mechanism and sealing mechanism of discontinuous curtain on groundwater seepage field were revealed.The results show that the groundwater level outside the curtain increased after the non-continuous curtain was applied,the water inflow velocity decreased and the runoff zone obviously weakened near the mine areas,and the non-continuous curtain in the karst area has strong feasibility and significant plugging effect.(5)The whole set of large-flow karst water gushing plugging method of"discontinuous curtain interception + key water channel exploration + grouting pad flow control +joint grouting plugging + treatment effect evaluation" was proposed.Combined with methods such as geophysical exploration,drilling and hydrological tracer tests,the position of discontinuous curtain blocking was determined effectively,and the target field of the main channel of karst water was accurately locked.By setting the flow control and slowing grouting pads,the water flow velocity in the pipeline can be effectively reduced,and the retention rate of slurry has been greatly improved in the grouting and sealing process.The new anti-dispersion grouting material was developed,the grouting plugging technology was optimized,and multi-key holes were combined and jointed together.Therefore,he high-efficiency plugging or sealing of the gushing water runoff channel of the karst pipeline has been realize successfully.(6)The research results have been successfully applied to the plugging of water gushing for the largest depressed limestone mine in China-Guangxi China Resources Cement(Pingnan)Hejing mining(single point water inflow 71200 m3/d),and the total water loss was 84300 m3/d.These research results ensured the normal safety production of the mine,and the theoretical systems of comprehensive management of water inrush or gushing were formed in the karst area.These results have important and significant guidance or reference for similar projects. |
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