Study On Mechanical Characteristics Of Freezing Wall Of Steel Pipe Frozen Soil Retaining Structure

Under the trend of the increasing complexity of urban rail transit lines,how to break through the traditional underground excavation support technology and put forward a more reasonable and safe construction technology is an urgent problem to be solved for underground construction projects.Taking the underground excavation support project of Jiangpu Road Station of Shanghai Metro Line 18 as the prototype,this paper combines the advantages of artificial freezing method and pipe shed method to form the pipe shed freezing reinforcement technology.By means of numerical simulation and model test,the stress and deformation law of the frozen wall retaining structure during excavation is studied,and some valuable conclusions are obtained.In the aspect of numerical simulation,ANSYS software is used to study the mechanical properties of the frozen wall structure.The arrangement of simulation calculation includes typical parameter test,single factor cycle test and orthogonal test.In the calculation of typical parameters,parameters were selected according to the engineering prototype,and the calculation model was simplified to obtain the instantaneous stress and deformation law of the composite structure of "pipe shed + frozen soil" under excavation and unloading,as well as the deformation characteristics of the frozen wall under the initial support.In the single factor test,the thickness of floor frozen wall,roof frozen wall,side frozen wall,pipe canopy diameter,excavation step,excavation sequence and cement content were selected as the influencing factors to study the influence of these factors on the mechanical properties of frozen wall structure.Orthogonal experiment was carried out for the selected factors,and the primary and secondary relationship of the influence of the horizontal change of each factor on the stress and deformation law of the frozen wall was obtained by range analysis method.In the aspect of model test,based on the similarity theory,the engineering prototype is simplified appropriately,the physical model of pipe shacking freezing is established,and the excavation simulation system is designed,so as to obtain the freezing temperature field data,the displacement field and stress field data in the excavation process and carry out the data analysis.In terms of data comparison and comprehensive analysis,the results of numerical simulation and model test were compared and analyzed in terms of displacement field and stress field,and the consistency of the laws obtained by the two research methods was mutually verified.The improvement of the model test is proposed,and the general rule of mechanical properties of frozen wall of frozen steel tubular permafrost envelope is obtained by summarizing the numerical simulation analysis.It has certain engineering practical significance.There are 55 figures,15 tables and 73 references in this paper.