Experimental Study On Multi-Tube Freezing Model Of High-Velocity Permeable Stratum

The artificial freezing method is one of the water stopping and strengthening methods widely used in the excavation of aquifer mines and tunnels.In the freezing method construction under moving water conditions,the seepage velocity and the important parameters affecting the freezing scheme can even Determine the success or failure of the freezing method construction.This paper takes saturated porous media under the condition of percolation as the research object,and establishes a large-scale similar model test method to explore the spatial-temporal evolution law of the artificial freezing method temperature field under a large flow rate;establishes a mathematical model of hydrothermal coupling,and combines experiments with numerical simulation The results verify the rationality of the mathematical model and use the model to optimize the frozen construction scheme.First,based on the similarity criterion,this paper takes saturated porous media as the research object,designs and establishes a large similar model test,measures the temperature change data at different percolation speeds in the single-row three-tube freezing process,and then analyzes the freezing temperature at different flow rates.Field space-time evolution law.Under seepage conditions,the development of the freezing front is actually the process in which the freezing tube absorbs the initial heat of the saturated porous medium,the latent heat of the phase change of the water,and the heat transfer by convection.At the same time,in the multi-tube freezing process,the cooling capacity of the adjacent freezing tubes is superimposed.It will produce the "group tube effect" and accelerate the expansion of the freezing front;the size of the seepage velocity directly affects the convective heat transfer and the "group tube effect",which in turn affects the frozen wall intersection time and the frozen wall thickness at different positions.When the velocity is less than 3m/d,the induction radius of the "group tube effect"is 400mm;when the velocity is 6m/d and 9m/d,the induction radius of the "group tube effect"is 154mm and 130mm,respectively.Then,based on the apparent heat capacity method,a mathematical model of water-heat coupling is established,and a numerical calculation model of COMSOL Multiphysics is established.The function of the custom partial differential equations in the software is used to realize the numerical value of the coupling problem of the temperature field and the seepage field in a saturated porous medium The solution,combined with experimental data,verified the rationality of the hydro-thermal coupling model and the accuracy of parameter selection.Finally,using the mathematical model of hydrothermal coupling and combining the time and space and evolution of the freezing temperature field under seepage conditions,the freezing method construction scheme of the auxiliary shaft in the Huainan Panyi Coal Mine was optimized.At 20m/d,the optimized scheme has 7d,13d,and 57d advancements in the frozen wall crossing time compared to the conventional scheme at three flow rates,respectively,indicating that the optimization effect is good and the larger the flow rate,the more significant the improvement.Figure[48]table[14]reference[88]...