Experimental Study On Static And Dynamic Characteristics Of Clay-containing Sand Based On Fine Content And Mineral Composition

Under the action of cyclic loading,the sand will be liquefied and destroyed.Most of the previous research work focused on pure sand,but in nature more clay-containing sand with fine grains.Unlike pure sand,clay-containing sand contains two matrices,coarse-grained and fine-grained.At present,more and more scholars have discovered the liquefaction of clay-containing sand in earthquakes.There are contradictions in the research results of existing scholars.The conclusions that adding fine particles to pure sand will increase or decrease the resistance to liquefaction or have almost no effect on the resistance to liquefaction have been reported.At present,more scholars only use a specific type of fine-grained soil and pure sand to carry out research,not paying enough attention to the influence of mineral composition,and the experimental conditions are relatively simple and lack of mutual comparison.At the same time,based on the two factors of fine particle content and mineral composition,the research results using multiple test conditions to compare each other are still quite limited.In this paper,Toyora Sand is used as coarse grain,and two mixed fine-grained soils with the same plasticity index but different mineral composition are used as fine grains.After mixing,clay-containing sands with different fine grain contents are obtained,which is useful for controlling relative compactness.Two test groups with the same and the same inter-particle void ratio were subjected to a triaxial monotonic shear test and a triaxial cyclic shear test,and the test results were compared with each other.The main conclusions are as follows:(1)The content of fine particles has an important influence on the static and dynamic characteristics of clay-containing sand.On the one hand,increasing the content of fine particles will cause significant changes in the stress-strain relationship of clay-containing sands,the development law of excess pore water pressure,shear strength indexes and effective stress paths.For example,the stress-strain relationship changes from strain softening to strain hardening.And other phenomena,the shear strength index will first decrease and then increase.On the other hand,increasing the content of fine particles will cause the liquefaction resistance of clay-containing sands to decrease first and then increase.(2)The mineral composition has an important influence on the static and dynamic characteristics of clay-bearing sand.Although the plasticity index of the two fine-grained soils is the same,the content of different fine-grained soil minerals will affect the static and dynamic characteristics of the soil.On the whole,when the content of fine particles is low,the content of clay minerals enhances the anti-liquefaction ability more obviously,and when the content of fine particles is high,the presence of montmorillonite enhances the anti-liquefaction ability more obvious.(3)There is a main peak point in the viscous energy dissipation ratio of clay-containing sand in the later stage of loading,and the value of cyclic stress ratio and fine particle content will significantly affect the height of this peak point.(4)When the relative density of clay-containing sand is controlled to be the same,the clay-containing sand with montmorillonite in the fine grains will produce a more obvious "energy competition" phenomenon,and control the intergranular pore ratio of the clay-containing sand.At the same time,clay-containing sand with higher clay content in fine grains will produce a more obvious "energy competition" phenomenon.