Experimental Study On Influence Of Groundwater Velocity On Freeze Temperature Field

The artificial freezing method has been widely used in underground engineering construction,and the freezing wall formed by this method has the advantages of temporary support and water stop.Because of the function of ground water,the development of frozen wall is uneven,which leads to engineering accident.According to the basic principle of similarity model theory,this paper establishes the model test device of sand layer freezing wall under the action of underground water seepage,and studies the development law of artificial freezing temperature field under the action of groundwater.By analyzing the results of single-tube and double-tube freezing at different flow rates,the influence of different seepage on frozen wall formation was obtained and the formation rule of frozen wall was briefly analyzed.(1)When there is no flow rate,the surrounding areas develop more evenly.When the flow rate is 5m / d,it can be seen that the downstream freeze develops at a faster rate than the upper reaches,resulting in a non-regular frozen section shape Compared with no flow rate,The thickness of freezing pipe was reduced by 22.4%,and the thickness of back water freezing front was reduced by 5.2%.Under the action of groundwater,there is a gap between the development of the frozen wall in the upper and lower reaches.When the flow rate is 5m / d,the ratio of the frozen wall thickness in the upper and lower reaches is 81.8%;when the flow rate is 10 m / d,31.1% and 9.4%.(2)During the process of double-tube freezing,the lap time became slower due to the water velocity.Under the experimental conditions,the lap time of 5m / d was about 24.5% d lap time is about 34.3% later than the no-flow condition.However,this difference in freezing will become smaller as the freeze time increases.By using the finite element software Comsol,the numerical calculation of the development law of freezing temperature field under the action of groundwater is established.By comparing the results of numerical calculation and model test,it can be found that the results of numerical calculation are in good agreement with the results of the model test,the test results of the temperature measurement are in agreement with most of the curve of the simulation results,and the reliability of the numerical calculation is verified,which provides a good experience for the later artificial freezing engineering and experiment.