Study On Deformation Characteristics Of The Pile-plank Subgrade In Seasonal Frozen Region

The problem of frost heaving and thawing settlement in seasonal frozen soil region will cause serious diseases of subgrade and deformation of upper track structure,thus threatening the safety and comfort of train operation.The existing pile-plank subgrade is widely used in foundation treatment to solve the settlement and deformation of high-speed railway subgrade.It has significant advantages in controlling the deformation of non-frozen soil areas subgrade,but it is rarely used in the foundation treatment measures in seasonal frozen soil areas.As a new type of frozen soil foundation treatment measure,the engineering applicability of pile-plank subgrade needs to be further studied.In this paper,the basic soil test is used to analyze the field soil properties,and the model test is used to analyze the internal temperature,moisture and displacement changes of pileplank subgrade under different working conditions.Finally,the supplementary analysis is carried out by numerical simulation,The research can provide some reference for the application of pile-plank subgrade in practical engineering.The main conclusions are as follows:(1)The results show that:under the high consolidation pressure,with the increase of fine particle content,the compression modulus of soil increases first and then decreases,and then increases,while under the low consolidation pressure,it basically decreases;The compactness and initial moisture content are positively correlated with the compression modulus.The three factors have significant differences on the compression modulus,and the compactness has the most significant effect on the compression modulus.(2)The shear strength of soil will change with the number of freeze-thaw cycles,fine particle content and confining pressure,and the fine particle content will change the stressstrain relationship of soil.Specifically,with the increase of fine particle content,the stress-strain curve of soil gradually changes from strain hardening type to strain softening type.(3)Through the model test,the changes of temperature,moisture and displacement in the subgrade under different negative temperature and different overlying loads are studied.The lower the temperature is,the greater the deformation is after freezing and thawing,and the obvious warping phenomenon appears in the bearing plate of pile-plank subgrade under negative temperature;The load can restrain water migration and frost heaving,it has a great influence on the distribution of temperature field in its influence range.(4)By comparing the two groups of tests before and after adding the insulation board,it is found that the insulation board has a good insulation effect on the foundation soil.On this basis,the performance of the insulation board is briefly analyzed.(5)The multi field coupling numerical calculation model is established,and its feasibility is verified by model test.The temperature,moisture and displacement changes in the test are analyzed.Combined with the model test,the applicability of the new pile-plank subgrade in seasonal frozen soil area is demonstrated.