Effect Of Fine Particle Content On Mechanical Property Of Yinchuan Fine Sand

Sand is widely distributed in northern Ningxia,and the Yinchuan Plain is located in the seismic zone.The frequent occurrence of the earthquake caused the building to collapse and the liquefaction of the sand,resulting in huge economic losses and casualties.For Yinchuan,the local sand has been shaken several times to increase the compactness.The fine sand content of Yinchuan sand in different areas are also different.At the same time,the water content of the sand foundation changes continuously when the Yellow River passes through the city.These factors will have a great impact on the mechanical properties of Yinchuan fine sand.At present,there is some progress in the study of the properties of fine-grained sand.However,most of them are based on sand in other places,which cannot cover sand in Yinchuan area.The second reason is that most of them not systematically study the strength characteristics,compressibility,collapsibility,static side pressure coefficient and dynamic performance.Based on the above problems,according to the actual situation of the project,the sand and fine-grained soil are matched according to a certain ratio,and the orthogonal test scheme is designed according to the factors of dry density,fine grain content and water content.Study the influence of dry density,fine particles and water content on sand strength index,compressibility coefficient,collapsibility coefficient and static side pressure coefficient;and orthogonal design scheme based on dry density,fine particle content and confining pressure to study the effects of dry density,fines content and confining pressure on dynamic performance of sand.Research indicates:(1)The cohesive force of fine-grained sand increases with the increase of dry density and fine-grain content,and decreases with the increase of water content.The internal friction angle increases linearly with the increase of dry density,and the water content trend is increasing first and then decreasing decreases approximately linearly with the increase of fine particle content.Dry density is the main factor affecting the strength index.The increase of fine particle content on the cohesion of sand is obvious and important.The influence of water content on the cohesion and internal friction angle of the strength index is small,which is a secondary factor.(2)When the vertical pressure is constant,the compression coefficient decreases nonlinearly with the dry density,and increases linearly with the increase of fine particle content and water content.At the same time,the collapsibility coefficient of the sample decreases with the increase of dry density,fine particle content and water content,but the compression water sensitivity of Yinchuan sand is low,which can be ignored in the foundation design.The primary and secondary order of the influence of various factors on compressibility and compressive water sensitivity are dry density,water content and fine particle content.Increasing dry density is the most effective measure to reduce the compressibility and compressive water sensitivity of Yinchuan fine sand.(3)The static side pressure coefficient k0 of Yinchuan fine sand has a linear decreasing relationship with the dry density,and it increases nonlinearly with the increase of the fine particle content,and decreases first and then increases with the increase of water content.The main reason for the change of the trend is the change of the particle arrangement structure,the influence of the matrix suction and the change of the hydrogen bond strength.(4)The cycle number of the sample is increased with the increase of dry density,and increases first and then decreases with the increase of fine particle content.The cycle number decreases with the increase of confining pressure.The improvement of the dynamic performance of the fine-grained sand can increase the time during which the sand foundation is subjected to the dynamic load or the large load in a short time,thereby reducing the damage of the building structure.The influence of confining pressure on the dynamic property of fine-grained sand is general.However,the effect of the three influencing factors on Young's modulus is not significant and can be ignored.(5)In the actual project,increasing the compactness of the sand foundation can significantly increase its various indicators to meet the needs of the project.When the fine particle content is about 15%,the sand has the strongest dynamic performance.The water content will have a certain impact on the performance of the sand.It is recommended to adjust the water content to a suitable value by using the soil layer to turn the sun,and use it for the project.Prevent the intrusion of water into foundation works and cause damage to the foundation.