Study On Dynamic Characteristics Of Compacted Loess Under Acid Condition

Along with the implementation and deepening of the strategy of the rise of central China,the highway engineering construction,which plays an critical role in promoting economic development,has been developing rapidly.As one of the most important provinces in Central China,Shanxi has large areas of loess,which brings about the use of loess as roadbed filler in highway construction.In recent years,the acid rain caused by fossil fuel burning in the development processing,on the addition of untreated wastewater discharged,contributing to the erosion of loess roadbed.Due to the special property of the loess,such as porosity and moisture,the highway roadbed which will be put into use is influenced by the long-term vibration of the traffic load,so that the dynamic characteristics of the roadbed is bound to be affected.In this paper,we used the British GDS dynamic three axis instrument to test the three axis of the remodeling sample.By analyzing the data collected during the loading process,the dynamic parameters of soil samples under acidic condition were analyzed systematically.The effects of pH ?,vibration frequency and age on dynamicparameters including dynamic elastic modulus,damping ratio and dynamic strength were studied.The results obtained in this paper are as follows:1.Dynamic elastic modulus(1)Under the same condition of frequency,confining pressure and pH ?,the dynamic elastic modulus decreases with the strain increasing,the decreasing process can be divided into three stages: slump stage,decline stage,stable stage.The dynamic elastic modulus decreases with the decrease of pH ? at constant dynamic strain.(2)Once the dynamic strain remain the same,the dynamic elastic modulus increases with the increase of the vibration frequency.The dynamic elastic modulus decreases with the increase of the dynamic strain,followed with the strain softening.At different age,the dynamic elastic modulus of the sample is consistent with the change of dynamic strain,and decreases with the increase of the strain.In the range of 3d-14 d,the dynamic elastic modulus is decreased gradually.In the range of 14d-60 d,the dynamic elastic modulus is gradually increasing,but the increase is small.2.Damping ratio(1)With the constant strain,the damping ratio decreases with the decrease of pH ?.The variation trends of the damping ratios of the samples with different pH ? acid erosion are basically consistent.The damping ratio increases with the increase of the dynamic strain,and the growth trend is gradually reduced.This is mainly due to the increase of strain,which leads tothe increase of the density of the soil.The energy consumption is increase,which leads to the increase of the damping ratio.(2)Keep the vibration frequency remain static,the damping ratio goes up with the increase of the dynamic strain.After the dynamic strain reached about8%,it eventually reach a plateau.Which indicates that the influence of the dynamic strain on the damping ratio is more obvious under the small strain condition,and the effect of the damping ratio is gradually weakened in the process of strain increasing.Under the same dynamic strain,the damping ratio rises with the increase of the vibration frequency.But when the strain reached8%,the damping ratio between different vibration frequency is subtle.(3)At different age,the damping ratio of the sample is basically consistent with the change of dynamic strain,and increases with the increase of the strain,but it gradually tends to be gentle after the dynamic strain reaches about 8%.In the range of 3d-14 d,the damping ratio is gradually decreased,and then remained stable.3.Dynamic strength(1)Under the same condition of pH ?,with the decrease of the dynamic stress,the vibration number is increasing when the failure criterion is reached.Under different p H ?,when the same dynamic stress is used,the vibration number decrease with the pH ? decrease when the failure criterion is reached.(2)Keep the vibration frequency remain static,with the decrease of the dynamic stress,the minimum vibration number to the failure criterion isincreasing.Under different frequency,when the same dynamic stress is used,the minimum vibration number to the failure criterion increase with the frequency increase.(3)Under the same condition of age,with the decrease of the dynamic stress,the minimum vibration number to the failure criterion is increasing.In the range of 3d-14 d,when dynamic stress remain the same,the minimum vibration number to the failure criterion decrease with the increase of age.In the range of 14d-60 d,the minimum vibration number to the failure criterion have decreased trend with the increase of age,but remains generally stable.