| As a method to strengthen underground soil,artificial freezing method has been widely used in the construction of the communication channel between urban subway lines.It can make the ground water and soil in the stratum form a frozen soil curtain with sufficient thickness,sufficient strength,water insulation and waterproof,which has a strong bearing capacity.However,as for the influence of excessive frost heave on underground pipelines,underground buildings and ground buildings in the freezing process of the tunnel contact channel by artificial freezing method,it has always been a key and difficult point that needs to be paid attention to in the project,how to understand and grasp the law of frost heave in the freezing process,so as to control the frost heave amount in the actual freezing project needs to be solved.In this thesis,the method of numerical simulation and physical model test is combined,and an intermittent freezing model is adopted to study the frost heave law of the tunnel contact channel.Firstly,the differential equation of temperature field is established by considering the heat transfer and the heat under the phase transition of ice water.The differential equation of water field is established considering that the temperature gradient difference in the freezing temperature field causes the water in the unfrozen region to migrate to the frozen region.Then,the hydro-thermal coupling differential equation is constructed through the connection of the relation equations based on the predecessors,and the relationship among unfrozen water content,volume ice content and temperature can be constructed.Secondly,COMSOL finite element software was used to establish a two-dimensional numerical calculation model of the tunnel connection channel,and the intermittent brine temperature was set.The mathematical differential equation module was used to conduct the hydrothermal coupling study,and then the solid mechanics module was added to form the hydrothermal coupling calculation model.Considering the influence of single factor brine temperature,freezing tube spacing,initial water content,temperature variation range and intermittent time on the frost heaving regularity of tunnel contact passage under intermittent freezing mode,orthogonal test was carried out at the same time to obtain the significant influence of the above factors on the frost heaving characteristic regularity of tunnel contact passage under intermittent freezing mode.Thirdly,the physical model test was carried out based on the similarity theory,and sensors such as thermocouple series,earth pressure box and displacement meter were arranged to monitor the data changes in the freezing test process,and the sensors were connected to the Datataker,and then the intermittent temperature of the cold bath was manually controlled,and the test data was recorded for research and analysis.Finally,the numerical simulation results were compared with the data obtained from the physical model test to judge the reliability of the numerical simulation calculation and prove the rationality of the frost heave characteristics under the intermittent freezing mode.The two verified and checked each other.It provides some reference for the effective control of frost heave when the artificial freezing method is used to strengthen the tunnel contact channel.This thesis has82 figures,19tables and107 references. |
