Study On Temperature Field Of Frozen Wall Of Cretaceous Soft Rock Shaft In Xinzhuang Coal Mine

Driven by the "One Belt And One Road" policy,the coal mining activities in western China had set off a new wave,which had also brought great challenges to the mine construction in this region.The freezing drilling technique used the circulating cold source provided by the freezing hole to take away the excess heat in the rock layer and form a solid freezing wall around the mine,which greatly improved the safety and reliability of construction and had been widely used in coal mine construction.Change rule of the temperature field of the frozen wall were the key factors affecting the method,while the western region in the cretaceous soft stratum,complex geological conditions,rock physical property and changeful,increased the difficulty of the freezing method construction,therefore in this paper,the cretaceous soft rock shaft to study the change rule of the temperature field of the frozen wall,provided reference for subsequent similar projects.The wind shaft project of Xinzhuang coal mine constructed by freezing method was taken as the background,the Cretaceous sandstone was selected as the research object,and the physical properties and thermal conductivity of medium-grained sandstone were systematically analyzed.Combined with the actual engineering situation of the mine and the previous research results,the finite element software ANSYS was used to simulate and analyze the temperature field of the frozen wall of the engineering mine,and the following results were obtained:(1)Based on the analysis of engineering survey results and laboratory test data of rock samples,the distribution characteristics and physical properties of the longitudinal cretaceous sandstone layer in the wind-shaft of Xinzhuang Coal mine were explored,and the factors affecting its thermal conductivity were discussed.(2)By studying the temperature field characteristics of soft rocks around two adjacent frozen pipes,it was concluded that the freezing depth is the same depth of frozen(-456m),different time node(freeze 8d,40d,81d,145d,200d,256d),double pipe freezing equably,water distribution in geotechnical engineering of heterogeneous rock mass in the process of freezing temperature field characteristics and differences,and it was concluded that the freezing rate because of rock and soil body heat physical properties difference and freeze frontal advancing speed change rule.(3)Based on the depth of nodes in the same time,different sandstone layer temperature field research,contrast in-456m,-540m,-640m,-740m and-828m deep freezing shaft radial temperature change curve and frozen wall in different time point of the temperature variation curves,the analysis of the soft rock at different depth of the freeze effect and frozen wall circle situation,system summarized the multi-tube freezing soft rock under the action of temperature field characteristics.The simulation results were compared with the measured data and the feasibility of the model is discussed.(4)On the premise of not changing the total cooling capacity,the freezing scheme was adjusted by changing the parameters such as the number,diameter and spacing of the freezing tubes,and the temperature field changes of the adjusted scheme were simulated,and the freezing scheme was optimized.