Study On Formation Mechanism Of Temperature Field By Artificial Freezing Method In Coastal Strata

The coastal areas of China are mostly structural soft clay strata.The coastal soft clay has engineering characteristics such as high water content,large porosity,high compressibility,low strength,strong structure and remarkable rheological properties.Previous excavation methods can not meet the needs of increasingly complex projects,while artificial freezing methods have excellent sealing performance,strong enclosing performance,convenient construction conditions and high strength freezing curtain.It has been widely popularized in various strata,especially in littoral water-rich clay strata.With the increasing scale of subway construction in our country,artificial freezing method has become the first engineering method in coastal stratum subway communication channel,shield tunnel end reinforcement,subway tunnel permeable accident repair and shield brush replacement in river and lake bottom tunnel.Study on formation Mechanism of formation freezing temperature Field by means of physical Mechanics Test,Field Measurement and numerical Simulation of Coastal artificial Frozen soil:1)based on the physical and mechanical tests of the frozen soil,the thermal conductivity of frozen sandy clay is obtained,the thermal conductivity of frozen sandy clay is 1.29 W / m ?,the freezing temperature is 1:-0.67 ?,and the specific heat is 1.29 k J / kg ?.2)the results obtained by artificial freezing method in coastal strata are as follows: the cooling rate of different depth is-18 m >-25 m >-10 m >-30.5m in the same temperature measuring hole.The results show that the cooling rate at-10 m is 0.924 ? / d ^-18m,the cooling rate is 1.089 ? /d ^-25m,and the cooling rate is 0.892 ? / d at 1.064 ? / d 30.5 m.Therefore,in the same freezing environment,the freezing rate increases first and then decreases.3)obtained by numerical simulation: the thickness of freezing curtain is 1.8 m after 45 days of freezing,and the freezing curtain develops quickly in the initial freezing period,but slow down in the intersecting circle,andthen the freezing speed gradually slows down.About 20 days to freeze the speed of freezing tends to stabilize.The numerical simulation of the project is carried out by using ANSYS software to obtain the cloud diagram of temperature field distribution,frozen cross circle diagram and freezing mean temperature change diagram.Compared with the field measured data,it is found that the numerical simulation results are good.It can reflect the actual situation of the project and provide reference for the freezing method of soft clay formation.