Influence Of Grain Size Grading On Site Soil And SH-reinforced Soil Salt Erosion Characteristics

In the thousands of years of Chinese civilization inheritance and continuation,a large number of cultural relics left precious historical information.As one of the most representative ones,earthen sites show inestimable historical value,cultural value,artistic value,scientific value and social value.The northwest region is the region with the widest distribution of desertification and desertified land in China.earthen sites are often built on the spot.The accompanying problem is that the uneven content of coarse and fine particles in the earthen sites is further lost under the action of wind,rain and other natural forces,which will evolve into various diseases,which seriously affect the stability of the structure of the earthen sites.In this paper,the water-salt capillary migration test was conducted to analyze the capillary property of the samples with different particle size gradations in salt solution and the influence of grain size gradation on the redistribution of water and salt in the process of capillary rising,so as to explore the influence of grain size gradation on the capillary rising property of the samples.The effects of particle size class on the physical and mechanical properties of the samples were studied by capillary wetting and drying cycle test of salt solution.Then,SH was used to reinforce the samples with different particle size gradations,and the same test method was used to observe the influence of particle size gradations on the soil salt erosion characteristics of SH reinforcement.Finally,ion chromatography test and mercury injection test(MIP)were carried out to analyze the microstructure of the samples.The main conclusions are as follows:(1)The time required for the site plain soil to be completely infiltrated by salt solution is shorter than that of SH reinforced soil,and the initial rate of capillary rise is higher than that of SH reinforced soil.Moreover,the higher the content of sand in the soil,the shorter the time required for the soil to be completely infiltrated by salt solution.The higher the sand content,the lower the water content and SO42-content of plain soil and SH reinforced soil.The increase of clay particle content can increase the capillary water absorption,and the addition of SH can prevent the capillary water from rising.(2)When the content of sand increased and the content of clay and silt decreased,the physical properties and mechanical strength of the soil decreased obviously,and the performance of the soil strengthened by SH improved in all aspects.The physical and mechanical properties of SH reinforced samples with higher content of clay particles after multiple salt cycles are better.(3)Through the dry and wet cycle of salt solution,the SO42-content of SH reinforced soil samples with different grain gradation is mainly concentrated at the top of the sample,and the salt resistance of the soil samples can be enhanced with the increase of clay particle content.When the clay particle content reaches a certain level,the salt resistance of the soil samples can be improved slightly with the increase of clay particle content.(4)Through mercury injection test,it is found that the more sand content in the site soil,the lower the porosity.The addition of SH enhances the bonding between soil particles and increases the porosity and fractal dimension of pore surface.Due to the destruction of salt crystallization,the porosity of SH reinforced samples increased and the surface fractal dimension decreased after salt cycling,and the damage of salt to SH reinforced samples with higher sand content was more serious.