Physical And Mechanical Properties Of Earthen Site Soil Under Snow Cover And Snow Water Infiltration

In the northeast,northwest and Qinghai-Tibet plateau where the ruins are located,snow often occurs in winter,even in spring and autumn.Snow cover the surface of the site.When the daytime temperature rises to a certain extent,the snow layer slowly melts,increases the water content of soil.The way of snow water infiltration from the top has an immersion effect on the surface and top of the site,the migration of moisture affected the strength of the soil particle skeleton,particle arrangement and other elements,which reduces the cohesion of the soil particles,changes the soil's microstructure and finally disintegrates.It eventually leads to the efflorescence on the top and scaling off under the external forces(wind erosion,human factors,etc.).When the temperature drops below 0?,the melting speed of the snow layer gradually slows down,and the snow water freezes in its pores,making the snow layer become a mixture of snow and ice.The dry and flake snow is densified and coarse-grained.The low temperature makes the liquid snow water entering the soil into solid ice.Because of the density difference between ice and water,the solid ice crystal volume is larger than that of water after phase transformation.This volume change and then squeezing pores is another reason for the deformation of soil grain skeleton.In order to explore the deterioration characteristics of the site soil under snow cover and control measures,the following aspects are studied in this paper: Under the same snow cover condition and different melting temperatures,the deterioration and failure characteristics and mechanism of the site soil were analyzed;At the same test temperature,the deterioration and failure characteristics and mechanism of the site soil were compared under the conditions of thin,thick snow cover and direct infiltration of unfrozen water(snow water);Three methods were used to reinforce the soil(the material is SH),and the freeze-thaw cycle tests under snow cover were carried out to explore the changes of its physical and mechanical properties.In addition,the disintegrating experiment was carried out on the reinforcement samples to explore their disintegrating resistance in water.(1)The results show that in the freeze-thaw cycles under snow cover,when the snow thickness and freezing temperature are constant,the cracks and efflorescence on the top of soil are more serious when melting temperature is 3?,followed by 6?,and the appearance of soil samples are basically unchanged at 9?.For soils with the same dry density,the physical and mechanical properties of soils after the test are different when melting temperatures are different.After 10 cycles,the frost heave rate of soil is the highest when melting temperature is 6?,followed by 9?,while 3? was the smallest.After the test,the longitudinal wave velocity and compressive strength of soil at the three melting temperatures have little difference,but the surface hardness increases with the melting temperature rise.(2)Under the same freeze-thaw environment,the influence of snow cover and direct infiltration of unfrozen water(snow water)on earthen ruins are quite different.Under the condition of snow cover,the deterioration of physical and mechanical properties and appearance of the samples during freeze-thaw cycles are obviously different from those of the samples directly infiltrated by the same amount of unfrozen water(snow water).In terms of physical properties,snow cover makes the frost heave rate of soil smaller,but efflorescence,cracks,scaling off are prone to occur on the top.As for mechanical properties,when the snow cover is small,the damage to the soil is less than that of the direct infiltration of unfrozen water(snow water).While if the snow cover gets thicker,the soil deteriorates slowly,this allows people to deal with diseases caused by the snow cover.(3)SH shows good reinforcement effect on soil in freeze-thaw cycles under snow cover.There are no crisp efflorescence and cracks in the soil samples,and the strength has also been improved.After the test,only a small amount of slag dropping appeared on the surface of the soil mixed with SH.The physical and mechanical properties increase with the solid content increasement(0.4%,0.5%,0.6%)of SH.(4)Sprinkling SH on the soil surface has little effect on strength improvement,but it has good locking effect on soil particles,so there is no slag dropping.In concentration selection,1.0% is better.After mixing + sprinkling SH,the extrinsic features of reinforced soil samples hardly change during the tests.Under the same spraying concentration,the higher the solid content,the better the reinforcement effect.The tests show that the three kinds of reinforced soil can maintain good water stability after freeze-thaw cycles under snow cover,and there is no disintegration during the disintegration test.