Salt And Wind Erosion Characteristics Of Earthen Site Solidified With SH-Lime Composite Materials

Earthen sites are direct physical evidence of the origin and evolution of Chinese civilization and have important historical,scientific,artistic,economic and social values.However,most of the earthen sites are preserved in the open air.The earthen site has been eroded by various diseases for a long time,so protection is urgently needed.The alternating development of salt erosion and wind erosion deterioration seriously affects the structural stability of the earthen site.How to reasonably and effectively control this kind of deterioration has become a tricky problem in the field of heritage conservation.At present,the most effective way is to use reinforcement materials for conservation.SH-Lime composite materials have the advantages of new polymer materials and traditional inorganic materials,and are often used in heritage conservation in the arid area of Northwest China.However,there are few studies on the characteristics of the composite under the action of salt erosion and wind erosion.Therefore,exploring the salt erosion and wind erosion characteristics of the solidified soil based on this material can provide a certain theoretical basis for the rational use of the material.Based on the application of SH-Lime composite solidified soil in earthen sites and the study of salt and wind erosion characteristics,through the study of water-salt capillary migration characteristics,this paper analyzes the capillary properties of the sample under different migration solutions and the redistribution law of water and salt in the sample through capillary rise,so as to understand the influence range and degree of salt solution on the soil in the process of capillary migration.Through the dry-wet cycle test with salt solution as well as the coupling test of dry-wet cycle and salt-wind erosion,the changes of basic properties such as apparent morphology,color difference,quality,hardness and wave velocity,and the changes of strength characteristics such as compressive strength,tensile strength and shear strength of solidified soil after the cycles were studied.The relationship between macro characteristics and internal microstructure was explored by ion chromatography test and mercury intrusion porosimetry test.The main conclusions are as follows:（1）The time difference of complete infiltration of different kinds of solutions in the unsolidified earthen site soil is small,the time is short,and the initial rate of capillary rise is high.The time of complete infiltration of the SH-Lime composite solidified soil by salt solution is much longer than that of deionized water.The moisture content in the unsolidified soil gradually decreases from bottom to top,while that of the solidified soil first increases and then decreases,which is related to the sample preparation method of double-sided compaction and the carbonization of lime on the surface at both ends of the sample.For the solidified soil,the preventing effect of the migration of chloride salt with water is better than that of sulfate salt.The capillarity of the unsolidified soil is stable,but the finger flow phenomenon appears in the solidified soil,which is inseparable from the addition of SH-Lime composite.（2）After the dry-wet cycle test with Na Cl solution,the unsolidified earthen site soil is cracked at the top and a large amount of salt precipitates on the surface,while a large number of crusts are formed on the surface and the samples are seriously deformed that with of Na₂SO₄ solution.After the coupling test of dry-wet cycle and salt-wind erosion,concave erosion is formed.Except for the formation of crusts and salt precipitation,the surface of solidified soil sample changes little.Compared with the unsolidified soil,the color of solidified soil without cycle tests is white as a whole.With the increase of the number of cycles,ΔL^*,Δa^*,Δb^*andΔE^*basically shows an increasing trend.The mass loss of solidified soil is lower than that of unsolidified soil,and can maintain a stable form after multiple cycles.The hardness of both unsolidified earthen site soil and solidified soil decreases with the increase of cycle times,the wave velocity of the unsolidified earthen site soil sample decreases with the increase of the number of cycles,while the wave velocity of the solidified soil sample increases and decreases alternately.After the coupling cycle test,the wave velocity even changes little compared with the initial value.（3）With the increase of cycle times,the compressive and tensile strength of unsolidified soil decrease rapidly,while that of solidified soil decrease steadily and tend to be stable.Compared with simple salt erosion cycle,the final stable compressive strength of solidified samples under the coupling cycle of salt erosion and wind erosion is higher.The cohesion and internal friction angle of unsolidified soil decrease after test,and that of solidified soil decrease gradually and tend to be stable.（4）After the dry-wet cycles with salt solution,with the increase of the number of cycles,the Cl^-content in the upper and lower parts of the solidified sample fluctuates greatly,and the Cl^-content in the middle fluctuates less.The SO₄^2-content of solidified soil shows a fluctuating upward trend.After the coupling cycle of salt erosion and wind erosion,the SO₄^2-content in each part of the solidified soil increases with the increase of the number of cycles.When the number of cycles is the same,compared with the simple salt erosion cycle,the SO₄^2-content in the solidified soil after the coupling cycle is generally low.（5）Under the combined action of salt or salt-wind,even if the shallow surface of solidified soil shows certain deterioration characteristics,its overall properties can still maintain a relatively stable state.The addition of SH-Lime composite reduces the overall porosity of the soil sample,and salt crystallization can fill the pores in the soil.