Study On Mechanical Characteristics Of Shaft Wall Under Freezing And Thawing Of Deep Alluvium

Coal will continue to be my country’s main energy source in the next few decades.As my country’s shallow mineral resources are on the verge of exhaustion,the deep part must be developed.To develop underground resources in deep surface soil areas,freezing sinking technology is currently the most widely used and successful technology.However,in the construction of freezing shaft sinking,the shaft wall deformation and rupture during the thawing phase of the frozen wall have long existed,and the safety and stability of the shaft wall of the newly built deeper shaft has become increasingly serious.The complexity and uncertainty of the external load is an important source of the shaft wall rupture during the thawing phase of the frozen wall in the deep topsoil.The essence is the deep freezing and thawing soil(frozen soil)-shaft wall structure interaction during the freezing wall thawing process.Cause the shaft wall structure damage caused by the force change of the shaft wall structure.From the available literature,compared with the research on shaft wall rupture or freezing wall strength and freeze-thaw process at the stage of mine production and operation,there is still a lack of research on this aspect so far.Therefore,this thesis takes the deep topsoil freezing method as the engineering background,through the combination of laboratory experiment and numerical simulation analysis to obtain the effect of the freezing wall thawing and thawing settlement on the vertical additional force on the shaft wall,the main research content and the results are as follows.Constructed a shaft wall stress test system under freezing and thawing action.The system includes a temperature control system,a measurement and acquisition system,and can obtain test data such as temperature,longitudinal displacement of the sample surface,and stress on the shaft wall.Under the action of the shaft wall force test method and conducted preliminary test inspection.According to the test results,curves of shaft wall structure stress-freeze-thaw time relationship,soil surface displacement-freeze-thaw time relationship,shaft wall structure stress-soil temperature relationship,and soil surface displacement-soil temperature relationship are obtained.The integration and analysis of the results put forward a linear regression equation of the additional force of shaft wall melt settlement under laboratory test conditions,soil temperature,burial depth and other factors.A numerical calculation analysis model corresponding to the laboratory test was established by using ABAQUS software.Based on the constant thermal parameters such as soil specific heat and latent heat,the temperature conduction rate was controlled to realize the change of the internal temperature of the soil with the number of calculation steps.The change is consistent with the change of laboratory test temperature over time,and the frost heave phenomenon is simulated by setting the expansion coefficient of the soil under different low temperature conditions.Comparing the results of the numerical simulation calculation with the laboratory test results,it is found that in the numerical simulation calculation,the variation law of the soil surface displacement and the stress of the shaft wall under the action of soil freezing and thawing with temperature is basically consistent with the laboratory test results.The analysis and research on the shaft wall force due to freezing and thawing of soil provides a basis.Based on the freezing construction conditions of a mine shaft,the additional force analysis model of the frozen soil thawing caisson wall was established.By carrying out the calculation and analysis of the shaft wall force characteristics under freezing and thawing,the additional shaft wall caused by the thawing and thawing of the deep topsoil frozen wall was obtained.The relationship between the force and the depth of the wellbore,and at the same time,the additional force level of melting and subsidence on the shaft wall of different buried depths in actual working conditions is predicted.The research results show that the additional force of thawing settlement on the shaft wall increases with the rise in temperature during the melting of the frozen soil,until the frozen soil is completely melted and stabilized,the additional force on the shaft lining increases with the increase in depth.