Study On Subgrade Deformation And Prevention Measures Of Gongyu Highway In Frozen Soil Swamp Area Under Complex Water And Heat Environment

In our country,the research of the permafrost on the Qinghai-Tibet Plateau has been gradually carried out as early as the construction of the Qinghai-Tibet Railway and Highway Engineering.After decades of development,there have been more mature theories and prevention measures for the deformation of railway embankments and low-grade highway embankments in permafrost regions.However,with the deepening of the western development and the increasing demand for economic construction,the construction of highways in permafrost regions will become normal.The contradiction between the instability of subgrade freezing and thawing and deformation caused by permafrost and the high standard of highway construction is extremely prominent,especially the prevention and treatment of subgrade deformation in frozen soil swamp area under complex water and heat environment has become a new problem.However,there are certain differences between highway subgrade and railway embankment,so it is impossible to copy some research results of Qinghai-Tibet Railway on subgrade deformation and prevention,and it is necessary to develop theories and prevention measures applicable to highway permafrost regions.This paper aims at the problem of subgrade deformation caused by the complex hydrothermal environment of the Gongyu Highway in the frozen soil swamp area,based on the "Key Technology Research of the Subgrade in the Permafrost Swamp Section of the Gongyu Highway " project,and the subgrade of the Gongyu Highway in the frozen soil swamp area as the research Subjects,using the methods of on-site investigation,indoor testing,deformation monitoring and numerical simulation,conducted the following studies:1.Research on the cause of complex hydrothermal environment in permafrost swamps.There is a natural water-heat balance in the formation of permafrost swamps in permafrost regions.This water-heat balance is beneficial to the protection of permafrost.However,the construction of the Highway is bound to destroy the original water-heat balance system,and then form a new and more complex water-heat environment.This paper analyzes the distribution of permafrost swamp areas along the Gongyu Highway and their engineering geological zoning characteristics.At the same time,climate,solar radiation,topography,stratigraphic lithology,hydrogeology,etc.are combined.The factors that affect the hydrothermal environment,and then analyze the causes of the complex hydrothermal environment from the aspects of complex hydrogeological environment,complex melting zone hydrothermal environment and complex engineering construction environment.Then it is concluded that the complex hydrothermal environment is mainly due to comprehensive factors such as water,heat,and engineering construction.This complex hydrothermal environment leads to the uniqueness of subgrade deformation characteristics.2.Research on deformation characteristics of subgrade in permafrost area.The complex hydrothermal environment exacerbates the frost heave and thaw settlement of the subgrade,which has a great influence on the stability of the subgrade.In order to accurately study the influence of the hydrothermal environment on the deformation characteristics of the subgrade,through the investigation of the existing G214 and Gongyu Highway subgrade diseases,combined with the distribution characteristics of each disease,in-depth analysis of the influencing factors,process and deformation of the Gongyu Highway subgrade under complex hydrothermal conditions Type characteristics.It is concluded that the deformation characteristics of subgrade are mainly manifested as subgrade subsidence,uneven settlement,slope instability,etc.In order to avoid this deformation(disease),it is necessary to conduct an in-depth study on the internal deformation mechanism.3.Study on the deformation mechanism of subgrade in frozen soil marsh area.Foundation soil and subgrade fillers constitute a new subgrade structure.This structure will produce a strong freeze-thaw phenomenon when building a new water-heat balance,and this freeze-thaw phenomenon will produce a large number of subgrade diseases.Particle analysis test,soluble salt test,compaction test,capillary water rise test,penetration test,frost heave characteristic test,freeze-thaw cycle test of subgrade filler in complex hydrothermal environment;frost heave test,particle analysis of foundation soil On the basis of the test,liquid-plastic limit test,and thawing sedimentation characteristic test,the freezing and thawing characteristics of the subgrade were deeply analyzed from the two microscopic aspects of subgrade filling and foundation soil.At the same time,in order to accurately study the impact of changes in the water and heat environment on the temperature field of the road base and the deformation of the subgrade,through the temperature field and displacement monitoring of the road base,the temperature field and deformation monitoring values of the road base at various stages of road construction are collected to analyze the complex water and heat environment in depth Under the monitoring section,the correlation between the temperature field of the subgrade and the settlement deformation.Combining the above two aspects of research,the mechanism of moisture migration,temperature field and freeze-thaw cycle of subgrade deformation are analyzed in depth from the mechanical point of view,and then the subgrade deformation mechanism of frozen soil marsh area under complex hydrothermal environment is summarized.It provides a theoretical basis for the scientific and effective use of deformation prevention measures,and has a guiding significance for the construction of roads in frozen soil marshes.4.Research on the prevention and cure measures of subgrade deformation in permafrost area.During the construction and operation of the original G214,a series of subgrade diseases appeared,and many prevention measures were adopted for different subgrade diseases.The core purpose of these measures is to solve the problem of water and heat balance,and artificially quickly make the subgrade and natural soil And the surrounding environment is integrated to build a new balance,thereby reducing the damage of subgrade caused by water and heat exchange.At present,the common single or simple compound subgrade prevention and control measures can only solve one aspect of the complex water and heat environment one-sidedly,and cannot fully adapt to the requirements of the complex water and heat environment.Therefore,it is necessary to develop a comprehensive set of remediation measures to adapt to the complex water and heat environment.In this paper,combined with the research results of the complex hydrothermal environment,the deformation characteristics of the subgrade,the deformation mechanism of the subgrade,seven prevention measures are proposed,and the characteristics of these seven prevention measures and the problems that can be solved are analyzed in detail.Through numerical analysis and comparative analysis of the effects of these seven control measures,a set of control measures suitable for subgrade deformation of Gongyu Highway frozen soil marsh area was developed.The newly proposed comprehensive prevention and control plan of heat rod + insulation board + sun visor + flake subgrade + sand cushion layer is better adapted to the construction environment of Gongyu Highway frozen soil marsh area,which not only solves the problem of subgrade heat energy but also solves the problem of subgrade drainage It has a significant effect on the deformation control of subgrade under complex water and heat environment,which can obviously increase the upper limit of permafrost in permafrost area,reduce the cumulative settlement of subgrade,and solve the complex hydrothermal environment problem in permafrost area.The successful application of this measure to the Gongyu Highway subgrade deformation prevention project has important practical significance.Through the above four aspects of research,we have mastered the cause of the complex hydrothermal environment in the Gongyu Highway frozen soil marsh area,studied the deformation characteristics and deformation mechanism of the subgrade under the complex hydrothermal environment,and proposed new comprehensive prevention measures.The results of this study have great significance for the construction and safe operation of highways in permafrost and swamp areas,with significant social and economic benefits.