Effect Of Irrigation On The Settlement Of High Railway Embankment In Loess Area

At present,the research on calculation model and calculation method of sedimentation deformation on loess embankment of high-speed rail are little,and experience for reference is not adequate.However,once loess embankments of high-speed rail have large sedimentation deformation will deform or affect the normal operation of high-speed rail,which brings great harm to safety of people’s lives and property,so the safety and stability of loess embankment cannot be ignored.This paper introduced the strength and deformation degradation equations which could considered the loess collapsible deformation in secondary development platform of ABAQUS.Thus the deformation analysis of high railway embankment considering loess collapsible characteristics was realized.Afterwards,the sedimentation analysis of high speed railway loess embankment under two types of humidification effects of farmland irrigation and water level raising was taken as an example to study the effects of various factors on the seepage and deformation of high speed railway loess embankment from the perspectives of irrigation factors,soil related parameters,ground water level change rate and water level rising position.The main results are as follows:(1)Based on the in-depth analysis of mechanical properties of loess,establish theoretical relations of loess deformation,strength parameter and moisture content,and write into corresponding calculation software on secondary development platform of ABAQUS,develop analysis methods of land weakening under the action of humidification.(2)This paper utilized the corresponding calculation software written in secondary development platform of ABAQUS.Firstly,the irrigation time was set as three days to study the impact of three different sprinkling irrigation intensities of 5mm/hr,10mm/hr and 15mm/hr on seepage field and settlement deformation of high speed railway loess embankment.Secondly,the sprinkling irrigation intensity was set as 10mm/hr to study the effects of different irrigation time of 1 day,2 days and 3 days on seepage field and settlement deformation of high speed railway loess embankment.The results show that: the settling volume at monitoring points of high speed railway loess embankment was gradually increased with the sprinkling irrigation intensity.When the irrigation intensity is 15mm/hr and irrigation time is 3 days,the infiltrationdepth of irrigation zone is 4m and the sedimentation amount on the surface of loess embankment is 1.2mm~1.6mm;Seven days after the end of irrigation,the infiltration depth is7 m and the sedimentation amount on the surface of loess embankment is 1.4mm~1.9mm.At this time,the infiltration amount in the center of embankment is 1.7mm.With the increase of irrigation time,the infiltration depth and range of irrigation area were amplified,which further increase the settling volume at monitoring points of high speed railway loess embankment.(3)Afterwards,the effect of saturated permeability coefficient and permeability coefficient ratio on seepage field and settlement deformation of high speed railway loess embankment from the aspects of soil saturated permeability coefficient of /1089.2sm-6?,/101sm-6? and/1089.2sm-7?,as well as the ratio of vertical and horizontal soil permeability coefficient of 2,5 and 10.The results show that: the settling volume at monitoring points of high speed railway loess embankment was gradually increased with the saturated permeability coefficient.When the saturated permeability coefficient is /1089.2sm-6?,when irrigate for three days,the infiltration depth of soil mass in irrigation district is 4m,the sedimentation amount on the surface of embankment is 1.2mm~1.6mm;7 days after the end of irrigation,the infiltration depth is 7m,the sedimentation amount on the surface of embankment is 1.3mm~1.8mm,and the infiltration amount in the center of embankment is 1.6mm;The settling volume at monitoring points of high speed railway loess embankment was gradually increased with the ratio of permeability coefficient.When the ratio of permeability coefficient is 10 and irrigate for3 days,the infiltration depth of soil mass is 5m,the sedimentation amount on the surface of embankment is 1.2mm~1.6mm;7 days after the end of irrigation,the infiltration depth is 10 m,the sedimentation amount on the surface of embankment is 1.6mm~2.4mm,and the infiltration amount in the center of embankment is 2mm.(4)Finally,the effects of three different groundwater level uplift rates of 5 meters in 30 days,10 meters in 30 days and 10 meters in 180 days,as well as the three different water level rising positions of 25 m,50m and 100 m on water level position and its settlement deformation of high speed railway loess embankment in different time were further studied.The results show that: the settling volume at monitoring points of high speed railway loess embankment was gradually increased with the increased rate of water level.When the rising place of water level remains the same,when rising 10 meters within 30 days,the rising time is one year,the the sedimentation amount on the surface of embankment is 16.3mm~17.6mm,the infiltration amount in the center of embankment is 17.7mm;The settling volume at monitoring points of high speed railway loess embankment was gradually reduced with the increased water level position.When the rising speed of water level remains the same,when the distance of rising place of water level and left slope toe is 25 m,after a year,the infiltration amount on the surfaceof embankment is 20.2~21.4mm,and the infiltration amount in the center of embankment is21.6mm.As for the influence of the changes of groundwater level on sedimentation deformation of embankment on high-speed rail in different forms,because at the earlier period of change of water level,the influence scope of water level rising is small,the water level of soil mass in the lower part of embankment is not affected,so the influence on embankment on high-speed rail at the earlier stage is insignificant.With the rise of water level,there is a large elevation difference on the both sides of water level line.At this stage,the infiltration rules of soil mass in embankment are “inclined corrugate”.When the rising time of water level is long enough,the changes of water level tend to be stable,at this time,infiltration rules of embankment are “symmetric corrugate”.