Study On Freeze-thaw Temperature Field Of Second Air Shaft In Dingji Mine

In recent years,due to the exploitation of coal resources,shallow coal is increasingly scarce.People began to excavate deeper coal seams,so the requirements for shafts are getting higher and higher,and freezing shaft sinking construction is therefore widely used.According to a large number of references,although people have done a lot of research on the freezing process of freezing method,there are still few studies on the melting stage of frozen wall after the end of freezing.Considering the influence of outlet temperature on the inner wall during the melting process of frozen wall,there are fewer studies on the development law of temperature field of frozen wall.In the whole process of freezing wall melting,the shaft is prone to water inrush accidents,resulting in a large amount of human and financial losses.Therefore,the study of the whole development stage of the frozen wall becomes more important.Under the premise of ensuring safety,the construction period is reduced as much as possible,the economic benefits are improved,and reliable technical guarantees are provided for the exploitation of rich mineral resources in the area.Its potential technical and economic benefits are very significant.In this paper,the second return air shaft of Dingji Mine is taken as the engineering background.Based on the thermal physical parameters of each stratum and the actual deviation of the freezing pipe in the field,the finite element simulation software is used to establish the freezing and thawing temperature field model.Through theoretical analysis and large-scale finite element calculation software ANSYS,the freezing and thawing stages of the frozen wall were simulated and analyzed respectively,and compared with the engineering measurement.During the freezing process,the intersection time of the four simulated layers of88 m fine sand layer,218 m medium sand layer,338 m clay layer and 485 m silty fine sand layer,the thickness and average temperature of the frozen wall from excavation to each layer were calculated and analyzed.It is concluded that the freezing wall intersection time is 485 m silty fine sand layer at the latest,and the intersection time is80 d.The thickness and average temperature of the frozen wall excavated to each layer meet the design requirements,which can effectively guide the on-site construction and shorten the construction period.In the process of melting,the four layers of 88 m fine sand layer,218 m medium sand layer,338 m clay layer and 485 m silty fine sand layer of melting temperature field are simulated and analyzed,and the time required for complete melting of each layer is calculated.In the process of melting,timely grouting between the walls is carried out.It is concluded that for the medium sand layer with a cumulative depth of 218 m in the second return air shaft of Dingji Mine,the shortest thawing time of the frozen wall is496 d,and the thawing ratio is about 1.69.According to the simulation results,wall grouting was started at 480 days of shutdown.Through the monitoring of the measured grouting volume and grouting pressure effect,the design requirements are met.It is verified that ANSYS finite element analysis software can be used to simulate and analyze the freezing and thawing temperature field of frozen wall.Figure [59] Table [13] Reference [93]...