Study On Modification Of Ningxia Loess By Bentonite

Loess in the Ningxia region is widely distributed,collapsible strong,and prone to erosion,erosion and piping and other infiltration damage.Construction and water conservancy projects on the loess foundation in Ningxia are often caused by collapse of the loess foundation due to the failure of waterproofing,erosion and corrosion erosion,and increased frost heaving.Due to collapsible loess,infiltration deformation and freeze-thaw deformation,the building or structure settles,cracks and even destroys,resulting in huge economic losses.Ningxia area is arid,lack of water resources,water is the lifeblood of industrial and agricultural development in Ningxia,so water conservation is extremely important.Canal seepage prevention and landscape wetland seepage control are important ways to save water,but the existing impervious measures are not ideal.The main mineral composition of bentonite is montmorillonite,which has high water expansibility,adsorption and ion exchangeability.Incorporating it into soil can significantly improve soil impermeability.At present,some progress has been made in the study on the impermeability of bentonite into clay as impermeable material and for improving the impermeability of clay,however,few studies have been done to improve the permeability of loess in Ningxia while satisfying the strength,compressibility and collapsibility of loess in Ningxia.Therefore,it is of great significance to study the impermeability,strength characteristics,compressibility and collapsibility of modified loess to improve the impermeability of buildings and water conservancy projects in Ningxia.Based on the above problems,according to the actual situation of the project,mix the loess and bentonite in a certain proportion,taking bentonite content as the main factor,the scheme of single factor experiment was designed.Taking the degree of compaction,saturation and bentonite content as factors,orthogonal experimental design was designed to study the influence of compaction,saturation and bentonite content on the impermeability,strength,compressibility and collapsibility of modified loess.Researches indicate:(1)When the amount of bentonite was less than 3%,the permeability coefficient of the sample first decreased and then increased,and the change was greater.The permeability coefficient of the sample as a whole increased with the increase in the amount of bentonite.The degree of compaction has a favorable effect on the reduction of the permeability coefficient,and the greater the degree of compaction,the greater the magnitude of the reduction of the permeability coefficient.The degree of compaction and the amount of bentonite have a significant influence on the permeability coefficient.The amount of bentonite added to the permeability coefficient is the most important factor that affects the permeability coefficient.(2)Cohesion increased with the compaction degree and the content of bentonite,but decreased with the increase of saturation.The order of the factors affecting cohesion is compaction degree,saturation,and bentonite content.The internal friction angle increases with the increase of compaction degree and decreases with the increase of saturation and bentonite addition.The order of the influence of each factor on the internal friction angle is saturation,compaction,and amount of bentonite.The change in the amount of bentonite does not have a significant effect on the shear strength of loess.(3)The compressive modulus is inversely proportional to the compressibility.The compressibility decreases with the increase of compaction degree,increases with the increase of saturation,and increases with the increase of the content of bentonite.The order of the primary and secondary factors affecting the compressibility is the degree of compaction,saturation and content of bentonite.(4)Loess in Ningxia Tongxin collapsible strongly,increasing soil compaction degree can reduce the loess collapsibility.The incorporation of bentonite into loess can effectively reduce the amount of collapsible loess collapses in Ningxia Tongxin,which is of great significance as a seepage-proof material into Ningxia loess and improve the collapsibility of loess.(5)The optimal combination should take into account economic and bentonite modified loess impermeability,strength characteristics,compressibility and collapsibility.The loess project generally requires a degree of compaction of 0.94 to 0.96.Under the premise of meeting the engineering requirements,bentonite should be mixed as little as possible.Therefore,the reasonable amount of bentonite is determined to be approximately 3.0%,and the saturation is approximately 35%.