Spatiotemporal evolution of three-dimensional freezing temperature field in open-cut section of inclined shaft in water-rich sand layer
In order to solve the engineering problem that the excavation time and speed cannot be determined due to the difficulty of accurately predicting the freezing temperature field in the open-cut section of freezing inclined shaft during construction,we took the open-cut section of frozen inclined shaft in Shengfu Coal Mine as the research object,based on the field measured formation characteristics and freezing hole layout parameters,constructed the three-dimensional numerical calculation model of freezing temperature field by using COMSOL Multiphysics finite element software,and analyzed the temporal and spatial evolution of temperature field during open-cut section of freezing inclined shaft with numerical calculation.The results showed that the average freezing temperature of fine sand layer was 0.28～2.39℃lower than that of middle sand layer,and the effective freezing thickness of fine sand layer was 0.36～0.59 m thicker than that of middle sand layer.After continuous freezing for 88 days,the average temperature of the frozen wall in the open-cut section was lower than-12℃,and the side frozen walls at different levels were thicker than 4 m,and the frozen wall at the bottom was thicker than 5 m,which met the design excavation requirements.During the excavation,the exposed soil mass at the well wall had the phenomenon of"heat flow erosion",but under the conditions of rapid excavation construction,the effective thickness of the frozen wall did not decrease and the average temperature of the frozen wall was still below-10℃,so the phenomenon of"softening"of the frozen wall did not occur in a wide range during the excavation.Based on the predicted results,we proposed a site excavation plan.According to the field measured data,the temperature of the measuring point and well wall fluctuated slightly during the excavation process,but the overall temperature development trend was relatively stable,indicating that the frozen wall was safe and stable during construction.This study can provide reference for safe construction and optimal design of inclined shaft freezing method.
artificial ground freezing methodinclined shaftopen-cut methodfreezing temperature fieldthree-dimensional numerical modeling
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