Experimental Study On Dynamic Liquefaction Of Saturated Silty Sand

Currently, For fines content, there are few dynamic liquefaction tests on saturated sand being carried out. Only for the content of fines, The researchers carried out experimental studies on indoor dynamic triaxial tests. Analysed the influence on dynamic elastic modulus, dynamic strength and dynamic pore water pressure ect. of the saturated sand,which has different levels of fines. But didn’t reached the same result yet.This paper considered the different types of fines(mean particle size d50 is different), that is to say, this paper takes the content of fines Fn and the ratio of the mean particle size D50/d50 into account(D50-the mean particle size of sand and d50-the mean particle size of fines). Under the different kinds of fines, Studied the influence on dynamic axial strain, dynamic elastic modulus, dynamic strength and dynamic pore water pressure of the saturated sand,which has different levels of fines. The main contents:The liquefaction tests are performed by a multi-function triaxial apparatus of Huaqiao University. Under the different ratios of the mean particle size(D50/d50=14,5,3),Studied the influence on dynamic axial strain, dynamic elastic modulus, dynamic strength and dynamic pore water pressure of the saturated sand. In these tests, the fines content of sand increases as 0%,5%,15%,20%,30%,45%. The results shows that:1. The mean particle size ratio D50/d50 and the fines content bigger, the growth of accumulated dynamic axial strain ?d faster. And the sample liquefied more easily.2. Dynamic elastic modulus Ed occurs the phenomenon of strain softening with the increase of strain. The maximum value Ed of dynamic elastic modulus shows irregular variation,which decreases first and then increases, with the increase of fines content. The critical fines content is about 20%~30%. When the fines content is less than the critical fines content, the greater the mean particle size ratio D50/d50,the smaller the maximum value Ed of dynamic elastic modulus. When it exceeds the critical fines content, the maximum value Ed of dynamic elastic modulus shows irregular variation,which decreases first and then increases, with the increase of the ratio of the mean particle size.3. Dynamic shear strength ?d shows irregular variation,which decreases first and then increases, with the increase of fines content. The critical fines content is about 20%~30%,and it reduced gradually with the increase of vibration times. The effect on dynamic shear strength ?d of the ratio of the mean particle size D50/d50 is that the maximum value of dynamic shear strength ?d decreases with the increase of the ratio of the mean particle size D50/d50. The greater the ratio of the mean particle size D50/d50,the larger the rate of the reduction of the value of dynamic shear strength ?d with the increase of vibration times, the smaller the contrary.4. Under the same test conditions, analysed the effect on dynamic pore water pressure of the saturated sand. The results shows that,when the ratio of mean particle diameter is 14(D50/d50 =14),the fitting effect of the classical pore pressure model of Seed is poor, but Using the modified exponential model can express the development law of dynamic pore pressure better. when the ratio of mean particle size is relatively small(D50/d50 =5、3), the development law of dynamic pore pressure is in full compliance with the classical model of Seed.