Experimental Study Of The Effect Of Alternating Wet And Dry On The Erodibility Of Sodium Sulfate Crusts

Salt dust storms,as a special type of dust storms,usually originate from dry lake beds in arid and semi-arid regions and are more hazardous than ordinary dust storms because the salt dust particles they carry are highly corrosive and toxic,seriously endangering regional and global ecosystems and human health.Salt crusts are widely present on the surface of dry lake beds,and the cementation of salt and soil particles can greatly increase the threshold wind speed of particles,thus effectively inhibiting the release of salt dust particles from the surface.However,the alternating wet and dry conditions caused by environmental factors can change the physicochemical properties of salt crusts and thus affect their erodibility,which make salt crust itself possibly become a new source of salt dust release and provide material source for the occurrence of salt dust storms.Wind transport of near-surface particles is the main driving force of salt dust release,while the natural climate change makes the salt crust constantly in the alternating change of wetting and drying,the current research has rarely considered the effect of wind and alternating wet and dry coupling on the physical properties and erosion of salt crust,so it is necessary to carry out research related to the effect of alternating wet and dry on the erodibility of salt crust,which not only helps to deeply understand the mechanism of salt dust release from dry lake beds,and then can be a comprehensive and systematic understanding of salt dust storms,but also can provide favorable guidance for ecological construction and disaster warning and prevention in arid and semi-arid areas,which is of great scientific significance.Sodium sulfate is a common and widespread type of salt in dry lake beds in arid and semi-arid regions.For this reason,this paper was use blown sand physics and soil physics as the theoretical basis,and combined with wind tunnel experiments,shear strength experiments,and bulk weight measurement experiments to jointly analyze the mechanism of salt dust release from the surface of sodium sulfate crusts under alternating dry and wet conditions from both wind erosion physics and micromechanical properties of crusts.In this paper,through the self-made sodium sulfate crust,four different salt contents,three wind speeds and six dry wet cycle times are designed to explore the effects of different salt contents and different dry wet cycle times on the physical properties and Erodibility of salt crust,and the effect of the interaction between salt content and dry and wet cycles on the erodibility of salt crusts was also analyzed in detail using statistical knowledge and methods.The wind tunnel test results show that the wind erosion intensity presents the growth trend of power function and exponential function with the increase of salt content and wind speed,respectively.In addition,with the increase of the number of dry-wet cycles,the wind erosion intensity of the crust with different salt content shows a dynamic trend of increasing first and then stable,and the wind erosion intensity increases significantly and the highest after one dry-wet cycle,while the increase of wind erosion intensity decreases and gradually reaches stable after three dry-wet cycles.The experiments of shear strength and bulk weight determination showed that the alternating wet and dry effects caused significant changes in the structure of salt crusts,and the internal friction angle of salt crusts with four different salt contents increased and then decreased with the increase of wet and dry cycles,and then decreased and then increased with the increase of salt content.The changes in cohesion and bulk weight were more complicated,and the trends of both were consistent.When they did not experience wet and dry cycles,the cohesion and bulk weight of salt crusts showed an increase and then decrease with the increase of salt content.After they experienced wet and dry cycles,both decreased with the increase of wet and dry cycles times and salt content,while the cohesion and bulk weight of salt-free crusts increased with the increase of wet and dry cycles times.The multi-factor ANOVA showed that salt content,wind speed and number of wet and dry cycles all had significant effects on the erodibility of sodium sulfate crusts,and the effects of salt content and the number of wet and dry cycles on the erodibility of sodium sulfate salt crusts were greater than the effects of their interaction with wind speed on the erodibility of salt crusts,respectively.