Experimental Study On Dynamic Characteristics Of The Clay

With the massive construction of railways,the dynamic stability and long-term uneven settlement of subgrade soils under long-term high-speed train cyclic loading often cause excessive deformation of the subgrade and lead to instability and damage of the subgrade which poses a huge safety risk to the normal operation of the railway.Therefore,it is very important to study the dynamic characteristics of soil under cyclic loading.Under this background,the dynamic triaxial test with different frequencies and different dynamic stress amplitudes for the clay from Leshan to Guiyang section of Chengdu-Guizhou railway was carried out by using the dynamic triaxial apparatus of GCTS,aiming to provide guidance and reference value for the roadbed construction and disaster prevention of the Chengdu-Guizhou railway.The main contents of the experiment and the results are as follows:(1)The basic physical parameters of soil samples were obtained through particle analysis test,liquid plastic-limit measurement,and compaction test.By analyzing the test data,the soil samples were designated as low liquid-limit clay with good gradation.(2)The dynamic triaxial test with different frequencies(1Hz,2Hz,3Hz)and different dynamic stress amplitudes(30kPa,60 kPa,90kPa)was carried out through the GCTS dynamic triaxial apparatus combined with the characteristics of high-speed train loads.The dynamic triaxial specimens were prepared with the optimum moisture content,and the saturation mode was back pressure saturation.Cyclic loading was performed under unequal consolidation and drainage conditions.The frequency and dynamic stress amplitudes were analyzed for the dynamic strain,dynamic elasticity,modulus and damping ratio of the low liquid limit clay.(3)By analyzing the influence of frequency and dynamic stress amplitude on the dynamic strain,results show that the dynamic strain increases linearly and reaches a stable value after reaching a certain vibration.The stable value increases with the magnitude of dynamic stress.As the frequency increases,it increases first and then decreases.It is proposed that under the same dynamic stress amplitude condition,there may exist a natural frequency value that can make the dynamic strain and the dynamic elastic modulus reach the maximum value.(4)By analyzing the characteristics of maximum dynamic elastic modulus and damping ratio,it is found that when the dynamic stress amplitude is larger and the frequency is smaller,the maximum dynamic elastic modulus is larger and the damping ratio is also larger.