A New Materials Research Which Keep Soil Impermeable And Rugged In Highway Slope In The Cold And Arid Region

Highway subgrade slope erosion mainly shows that soil on surface of slope are washed away or the whole slope lose its stability because of rain runoff,rainfall infiltrating and slope runoff.It is the most common problem in the field of highway.However,the protective measures is studied insufficiently.This paper combined the cold and arid weather featuring with the ecological and environmental characteristics of desertification,Aiming at gentle-dip soil slope to propose a new effective approach that unite seepage prevention with ecological restoration,A new materials research is carried out which keep soil impermeable and rugged in highway slope in the cold and arid region.Through the laboratory tests and theory analysis,this text studied the influence of the double polyethylene materials contents(0.0.125%,0.175%,0.225%,0.275%)on physical and mechanical properties of silty sand and different soil(the double polyethylene materials contents is 0.275%)including permeability,collapsibility and hear strength.Besides that,exploring soil erosion regularity,overland flow characteristics and scour resistance when the double polyethylene materials contents(0.275%)in the 0—15cm layers,Combined with the micro electron microscope scanning illuminates the strengthening mechanism of double polyethylene materials.Aiming at silty soil,get the regularity of additives 1#,2#,3# in double polyethylene material affection of compacted soil permeability and shearing compressive strength.Get the best admixture amount of materials.The finial compacted soil has the characters of good impermeability,high strength,resistance to collapse and freezing resistance.The larger admixture amount is,the higher influence will be.Through the test,silty soil has the best impermeability,resistance to collapse,shearing strength and better structural stability when the admixture amount is between 0.275%~0.325%(1#:0.2%—0.25%,2#:0.045%,3#0.03%,mass ratio with dry soil).Aiming at silty clay,silt and medium sand,soil has lower permeability,better resistance to collapse and higher shearing strength when the admixture amount is at 0.275%Double polyethylene material has strong capability resistance to freezing that silty clay and silty sand lose mass less than 1% after 12 saturation freezing and thawing cycle under-10?,-20? and 30?,strength loss less than 25%,volume expand very little,a few break appears after cycles,permeability get affected,but the compacted soil is generally stable.Double polyethylene material increase the capability of keeping water.In the process of freezing and thawing cycle,with the cycle increasing,water content continuously increase,silty clay could get over 30% and silty sand could get 27%.SEM test shows the physical and chemical action between double polyethylene material and soil grain.double polyethylene material compacted soil has smaller pore proportion and amount than normal soil,the double polyethylene material appears like thin film(envelop effect)or silk(net effect)on the soil grains,these make the tiny grains connected by the large molecule and become a entirety.This cementation relationship improve and enlarge the soil physical,chemical and mechanical property.Double polyethylene material increase the ability of soil resistance runoff srour of slope,including undeveloped slope erosion,low water infiltration,little sediment and high stability of slope.Concrete expression are as follows:(1)When material content is 0.275 %,including slow infiltrate,earlier water generation,barely develop sheet erosion and rill erosion,slower growth rate of water content at the same depth.(2)The results indicate that the main erosion type is sheet erosion about unreinforced slope,The largest sediment yield appeared in the rill erosion developing stage.As the erosion of slope that treated by double polyethylene material mainly is mild surface erosion and even will not appear.Then the strength of the soil is higher,particle reunion size is big,the erosion resistance is increased that lead to the sediment load is far below plain soil.(3)Double polyethylene material can slow water evaporation and enhance soil water holding capacity.Secondly,it make slow infiltrate,little infiltration water infiltrates and low pressure;Finally,it can improve soil structure,enhanced the stability of the soil;Though we should not overlook the increasing rainfall which increasing the runoff causing increasing infiltration and the final soil water content,erosion have little effect.Double polyethylene material is a new kind of composite material of fine property.Being hydrophilic,the double polyethylene materials\ can enhance water availability of soil and promote the growth and development of plants.Comparison of plain soil slope,the double polyethylene material is good at improving the germination rate of flower seeds and accelerating the growth of undergrowth vegetation.Vegetation was protected well on reinforcement slope after washing with water for a long period of time.But plants grow on the unreinforced slope which was swept away as plant roots were nuked.At seedling stage,the double polyethylene material can protect plants,There are two ways of planting to improve soil capability of anti-erosion.One is that fine root can keep soil by its net-work,other is that leaves keeps the rain in bad weather and the sun off in good in the mature stage.The application effect of double polyethylene material is remarkable for core drilling that the formations are loose,broken,collapsed or water-sensitive.Contemporary,The effect is pronounced when apply to the slope protection of highway subgrade slope distributed on the northwest drought cold region.