Research On Hydrothermal Evolution Mechanism And Freezing Scheme Optimization Of Artificial Frozen Gravel Layer In Seepage Field

As an important technical means of underground structure construction,the artificial freezing method is widely used in mines,subways,tunnels,and other engineering constructions.However,a large number of cases have shown that when there is a large groundwater flow rate in the local layer,the construction quality of the freezing method will be significantly reduced.While increasing engineering costs,the incidence of safety accidents has also increased.To improve the applicability of the artificial freezing method in high-permeability strata and ensure the rationality and economy of artificial freezing scheme design,this paper takes water-rich gravel stratum as the research object,through model tests and numerical simulations to explore the temperature field and the formation rule of the frozen wall,combined with the ant colony algorithm to construct the optimization design method of the freezing scheme,mainly obtained the following conclusions:(1)Under the influence of seepage,the temperature field distribution in the frozen formation is asymmetric,and the downstream temperature is significantly lower than the upstream.The greater the seepage velocity,the smaller the range of the upstream cooling capacity diffusion,the larger the range of the downstream cooling capacity diffusion,and the larger the temperature difference between the corresponding positions upstream and downstream.(2)Affected by the constant temperature water flow,compared with the downstream,the upstream frozen wall develops slower,the thickness of the frozen wall is thinner,the overall frozen wall develops unevenly,and the position of the frozen wall intersection shifts downstream.When the seepage velocity is large,the frozen wall at the center of the frozen tube is arc-shaped,and this position is the weak area of the frozen wall.(3)During the formation of the frozen wall,the primary factor affecting the frozen wall intersection is the distance between the freeze pipes,and the primary factor affecting the thickness of the upstream and downstream frozen walls is the groundwater flow rate.(4)A simulation model of the freezing scheme of the subway communication channel was established,and the optimization area of the freeze pipe position was determined according to the development form of the frozen body.A parameterized formula was further defined in combination with the Gaussian distribution function.(5)Based on the ant colony algorithm,a frozen tube layout optimization system was constructed.The trial calculation of the case shows that the freezing time can be shortened by 30.95% after the optimized layout,and the formed frozen wall has excellent engineering quality characteristics.Therefore,the optimization design method has a good optimization effect and has the value of further development and promotion.