Bentonite Modified The Properties Of Secondary Loess In Ningxia

In recent years,along with the social and economic development of our country and the progress of agricultural irrigation technology,the seepage prevention requirements of modern irrigation districts,urban lakes and building foundations have also been constantly increasing.How to improve the leakage of secondary loess area in Ningxia under the premise of meeting the requirements of strength and compressibility has become the hotspot of current research.Bentonite as a "universal earth" is widely distributed in our country,reserves,ranking second in the world,the main mineral composition of bentonite for the montmorillonite has a very high water swelling properties,the current bentonite impervious blanket applied to the channel,the foundation and lakes.Some progress has been made in the research of seepage control engineering of lakes and so on.However,There is little research on increasing the permeability of secondary locss by directly mixing bentonite as an impermeable material into the widely distributed secondary loess in Ningxia,which satisfies the strength and compression.Therefore,it is of high engineering value and practical significance to carry out experiments on the infiltration,strength,compression and collapse coefficient of bentonite-modified secondary loess.In order to study the influence of various factors on the engineering indexes,single factor experiment was carried out with sandy loess and loess as the research object.The sand content was set as 0%,15%,20%25%and 30%respectively.The compaction degree was set at 4 levels of 0.86,0.90,0.94 and 0.98.The relationship between permeability,strength,compaction and humidification of bentonite modified secondary loess and the ratio of sand content and the relationship between humidification and compaction was studied experimentally.Based on the factors of saturation,compaction degree,bentonite content and sand content,orthogonal design L16(45)was designed.Saturation was set at 4 levels of 35%,55%,75%and 95%Compaction was set at 4 levels of 0.86,0.90,0.94 and 0.98.The content of bentonite is set at 4 levels of 0%,1.5%,3.0%and 4.5%.Sand content is set at 15%,20%,25%and 30%,4 levels,the strength and compressibility of secondary loess modified by bentonite were studied experimentally.The orthogonal experiment scheme L16(45)was designed with the compaction degree,bentonite content and sand content as the factors.The compaction degree was set as 0.86 and 0.90,0.94 and 0.98 respectively.The content of bentonite was set at 4 levels of 0%,1.5%,3.0%and 4.5%.The sand content was set at 4 levels of 15%,20%,25%and 30%.The properties of bentonite modified secondary loess were studied experimentally.The permeability coefficient,strength index,compression coefficient and wet subsidence coefficient were measured by TST-55 type osmometer,ZJ type electric straightener and GZQ-1 type automatic pneumatic fixer.The law and significance of each factor were analyzed.The optimal combination was obtained with the compaction coefficient of 0.95 or 0.97 and the saturation of 65.5%/69%.The content of bentonite should meet the requirement of impermeability,to minimize mixing,in order to reduce costs;sandy rate of mechanical properties of loess little effect,can not be processed to save costs,the results show that:(1)With the increase of compaction degree and the increase of the content of bentonite,the permeability coefficient decreases obviously.With the increase of sand content,the permeability coefficient increases,but the effect is not obvious.(2)The compaction is beneficial to the improvement of the mechanical properties of loess and has the most significant effect.The mechanical properties of secondary loess decreased with increasing saturation.The ratio of sand content is unfavorable to mechanical properties but has no significant effect.The addition of bentonite to improve the impermeability of secondary loess will not have significant adverse effects on its mechanical properties.(3)The compressibility decreases nonlinearly with the increase of compaction dcgree,increases nonlinearly with the increase of saturation and bentonite content.With the sand content increasing first and then decreasing,the parabola trend of secondary loess.When the grit content is 25%,the compressibility is unfavorable,the content of bentonite is increased,and the compressibility of soil is increased.(4)With the increase of compaction degree and sand content,the collapsibility of secondary loess is weakened.