Research On Frozen Damage Mechanism And Treatment Technology Of Subgrade In Wuxi-Kuitun Intercity Railway

In seasonal frozen area,frozen damage has always been the main problem of railway subgrade construction,and it is the key factor to affect railway technical index and maintain stability of subgrade.With the change of seasons,diseases such as freezing and thawing,appearrepeatedly in railway subgradebuilt in seasonal frozen area,which reduces smoothness of the lineand has a negative impact on the operation of the train.Serious frozen damagehas appeared in some sections,station,culvert and bridge transition section of Wuxi-KuitunIntercity Railwayin recent years.Frost heaving phenomenon in cold season and thawing settlement phenomenon in warm seasonoften occur,which causes larger uneven deformation of railway subgrade,affects the line speed-increasing and endangers traffic safety seriously.Aiming at the subgrade frost damage problem of Wuxi–KuitunIntercity Railway,through field investigation,laboratory test and numerical method and theory analysis,engineering test,combined with the Wuxi –Kuitun region geology,hydrology,meteorology and cold data in line in recent years,distribution of subgrade frost damage,influencing factors and formation mechanism were studied.Based on this,the subgrade frost governance principles were put forwarded.Salting,lateral blind ditch,and lateral blind ditch combined with grouting engineering measures were adopted in the test sectionsubgrade.All kinds of engineering measures were effect evaluation,andthe applicable conditions of different measures were put forward.According to the researches,the following conclusions are drawn:(1)The subgrade frozen damage of Wuxi –Kuitunintercity railway in downlink distribution is relatively concentrated.The distribution of bridge and culvert gap is more,which accounts for about 70% of the total frost heavenumber.Most sections frost heave amount is between 10 ~ 15 mm,local road frost heave amount can be up to 25 mm.(2)The climate is cold in Wuxi –Kuitun region and subgrade filling is frost heaving sensitive soil,coupled with the high rate of soil water,which meet the conditions of frost heave.(3)The formation of frozen damage in general subgrade is related to the existence of railway ballastcapsule and accumulatedwaterofbedding.And the formation of frozen damage in transition section subgrade is related to free surfaceof subgrade soil.(4)Subgrade frozen damage regulation should adhere to the principle of "overall drainage,and secondly local strengthening".(5)Setting lateral blind ditch every hole and every other hole work well.Both of them can reduce the frost heaving amount to less than 4mm.The depth of sewer is proposed to set 0.6m.(6)The effect of setting lateral blind ditch every 4 holes is not particularly ideal.The frost heaving amount of 0.6m ditchdepth subgrade is up to 12 mm.The frost heaving amount of 0.8m ditchdepth subgrade is up to 8mm.(7)Theeffect of setting lateral blind ditch combined with grouting to copy subgrade cold damage in transition sectionis remarkable,which reduces the frost heaving amount to less than 3mm.This thesis provides experience accumulation for frozen damage regulation of railway subgrade in seasonal frozen area and has certain guiding significance for frozen damage regulation of railway subgrade in seasonal frozen area.The main innovation points:(1)According to the characteristics of Wuxi-Kuitunrailwayfrostdamage,grade classification of subgrade frost damage was put forward,and the types of frostdamage were dividedaccording to the location of frost damage.(2)The mechanism of frost damage in general subgrade and transition section subgrade was studied.(3)Setting lateral blind ditch was put forward as the main treatmentmeasure of generalsubgrade frozen damage,and the ditch spacing and depth wereput forward.(4)Setting lateral blind ditch combined with grouting engineering measures was put forward for frozen damageoftransition section subgrade,and suggestions on the ditch spacing were put forward in the end.