The Ptability Study On Subgrade Of Qinghai-tibet Railway Permafrost Regions

With the constant deepening of "western development" strategy in our country,especially of the qinghai-tibet railway construction,thus,the stability of railway roadbed is highlighted,and caused widespread concern.In order to serve the railway construction of permafrost regions,avoiding the disease problems,providing reference to the frozen permafrost roadbed design and construction,such as for the research of railway roadbed stability.This paper describes the Tibetan frozen soil environment,such as:temperature,precipitation,solar radiation,wind,etc.The author introduces the characteristics of permafrost,further to study the distribution of permafrost,physical properties and thermal physical properties,mechanical properties and the characteristics of freezing and thawing,thus cleared the permafrost of general characteristics and the rule temperature change.Using the scaled finite element simulation software ADINA,we analysis the flaky layer roadbed and ripped-rock embankment of the qinghai-tibet railway.Through establish the above two kinds of simulation model of roadbed,in the model with reference to the actual engineering situation,set the boundary conditions of the model.At the same time,the soil layers,and the heat conduction coefficient,specific heat,density parameters,respectively gives to the layers of soil,using the Structures in the module and Thermal module of ADINA to solve.Record the next 50 years in the solving process of temperature field and the change of the settlement,in the end,calculate the temperature field cloud picture and cumulative settlement curve,and summarized and analyzed.In this article,through the simulation results of the frozen soil roadbed,we get the temperature change rule from temperature field,slope and temperature changes.Because of the disturbance fierce,flaky subgrade in the early part of the building,temperature field change is bigger,then stable year by year.0? isotherm contrast moved up year by year,this shows that has good protection function for the deep underground permafrost,is advantageous to the subgrade stability.The temperature field cloud picture appear asymmetry,it shows that the effect significantly of the sunny and shady slope,for the negative impact of the subgrade stability cannot be ignored.The temperature of surface and base of ripped-rock embankment was increased,it shows that the impact of climate warming on subgrade is great.The temperature difference value of 1 m deep slope of sunny and shady after 15 years maintains stable,it shows the ripped-rock revetment of regulating temperature of sunny and shady slope has played a good role.From the sedimentation speed,the settlement of left and right shoulder,etc.,to analysis the rules of settlement changes.The settlement deformation caused by the severe disturbance of soil increased dramatically of the flaky embankment in the early part of the building.In the first year,the settlement deformation is the most serious,then settlement will be slow and stable year by year.As a result of the existence of slope effect of sunny and shady,the settlement of the left shoulder is greater than the right shoulder's,this uneven subsidence phenomenon is not conducive to the stability of subgrade.Five years after ripped-rock embankment in construction,subgrade deformation is large,and the settlement of the left shoulder is greater than the right shoulder's.With the continuous decrease of sedimentation rate,the settlement of subgrade is reduced.The first 15 years of time,the settlement difference between the left and the right shoulder be larger,since 20 years the settlement difference between the left and the right shoulder decrease obviously.Though,this paper got some conclusions and regularity,and reference for practical engineering,but there are still shortcomings and problems to be solved.Therefore,this article also put forward the deficiency of this topic,and Put forward the prospect of future research and idea.