Experimental Research On The Engineering Property Of Sulphate Saline Soil In Ningxia Area

Sulphate soil as a special soil,distributed in all regions of the world widely,sulphate saline soil of our country are mainly distributed in the northwest region.Ningxia is located in arid and semi-arid region of Northwest China.dry climate,strong evaporation and great temperature difference in this area,therefore,formed a unique inland saline soil in arid and cold regions.Among them,the sulfate saline soil and sulfurous saline soil is widespread.Sulphate saline soil has the characteristics of salt expansion,dissolution and corrosion,the hazards of these properties are greater than collapsible loess in the engineering construction.With the development of the western development strategy and the the Belt and Road is implemented,Water,road,railway and housing construction will continue to increase in the saline soil area,this will encounter the problem of sulphate soil.Therefore,the study on engineering characteristics of sulphate salty soil is especially urgent and necessary.In this dissertation,wuzhong City HONGSIBU sulphate saline soil to test the soil,by artificial preparation of sulfate saline soil as research object,the effects of compaction degree,salt content,water content and temperature on the strength,swelling and compression of sulphate saline soil were studied,and study on the salt expansion characteristics of sulfate saline soil by calcium chloride and fly ash.The following conclusions are drawn through the experimental study:(1)The degree of compaction and water content have enhanced effect on cohesion in a certain range,but beyond a certain threshold will reduce the cohesion,the amount of salt and the number of freeze-thaw cycles have a decreasing effect on cohesion.Various factors have a great influence on the cohesionm,the internal friction angle is less affected by the above factors.(2)For the salt heaving rate of sulphate soil,the effect of salt content was significant,and other factors were not significant,salt content has an increasing effect on salt expansion.For compression coefficient,the effect of salt content was extremely significant,the number of freeze-thaw cycles was significant,and the influence of other factors was not significant,the increase of salt content and freezing thawing times will increase the compressibility.(3)Under the condition of unilateral cooling,the swelling temperature of sulfate saline soil increases with the increase of salt content.With the decrease of temperature,the process of salt and frost heaving appears as four stages:35?5 ? belongs to the pure salt expansion stage,5?5?belongs to the adjustment stage,-5?10? belongs to the salt and frost heaving stage,-10?-25?belongs to the stable stage.(4)Through the experiment of improving the salt swelling of sulfuric acid soil at room temperature,the optimal dosage of fly ash is 20%,The optimal dosage of Cacl2 is 2%,The inhibitory effect of Cacl2 on salt swelling was obvious.This dissertation studies the engineering characteristics of sulphate soil in Ningxia by indoor experiment,to provide reference and technical support for the engineering construction in the area of sulphate soil.