Dynamic Characteristics Of Loess In Xianyang Based On Analysis Of Its Microstructure

The loess is widely distributed in China,and the Loess Plateau in the northwest is the largest loess plateau in the world.The Loess plain in North China is also the largest loess plain in the world.Loess areas prone to earthquake disasters.Due to the loess with large porosity,loose,changing met water features,earthquake disasters caused by loess are particularly serious.With the 18 th CPC National Congress,deepening of the eighteen western development,the construction of the western region is increasing,and the dynamic stability of loess must be considered in the construction of the project.The dynamic characteristics of loess involve many contents and wide range.Most domestic and foreign scholars have focused on multi-stage loading,by controlling the confining pressure,consolidation ratio,frequency,waveform test conditions such as a series of studies on the dynamic characteristics of loess,however the research on the dynamic characteristics of loess single stage loading involves less.Most of the research is focused on the macro perspective,there are still some deficiencies in the study of the dynamic characteristics of loess from the micro perspective and the relationship between microstructure parameters and macro dynamics parameters.This paper is supported by the National Natural Science Foundation of China,"the study on the evolution of microstructure and strength of typical loess under different dynamic loads".Based on the basic physical and mechanical properties of the samples taken from the Xianyang area,the single stage loading dynamic triaxial test of loess samples is respectively in different confining pressure,waveform,frequency and amplitude,and the influence of confining pressure waveform,frequency and amplitude of dynamic characteristics of loess is analyzed.The microstructures of the samples were obtained at different stages of the dynamic triaxial test,and the images were processed with ipp6.0 and Photoshop image processing software.The samples at different stages under different test conditions were analyzed in the average diameter,abundance,circularity,fractal dimension,directional probability entropy and other microstructure parameters of the law of change.The article makes a further analysis by use of the theory of grey correlation degree between sample microstructure parameters and dynamic modulus of elasticity.The results show that the waveform,frequency,confining pressure and amplitude have great influence on the dynamic characteristics of Xianyang loess.Relative to the sine wave,square wave,sawtooth wave are more likely to make the Xianyang loess deformation,and the dynamic elastic modulus value is relatively small;The higher the confining pressure is,the harder the deformation of the specimen is,and the bigger the dynamic elastic modulus is.The higher the frequency is,the easier the deformation of the specimen is,the smaller the dynamic elastic modulus is.The high amplitude is easier to make the loess deformation and the dynamic elastic modulus is smaller.The microstructure of loess in Xianyang is mainly composed of particles,pores and aggregates,and the particles are mainly flaky and columnar grains.Particle contact are mostly little contact and point contact,and particle and pore distribution is uneven.The content of agglomerates increased after the experiment under the condition of all dynamic loading test.The deformation of the specimen is mainly caused by the dislocation and destruction of the particle skeleton.Vibration to the test cycle time 12 times,particles and pores change law is not obvious.When the test reaches the limit state,the average diameter and area of the particles and the pores are reduced and the directional probability entropy increases.The law of abundance,circularity and fractal dimension is not obvious.In the limit state,there is a certain correlation between the microstructure parameters and the dynamic elastic modulus of the particles,and the correlation degree is as follows: the average diameter > fractal dimension> directional probability entropy> area> abundance> circularity.The relationship between the pore microstructure parameters and the dynamic elastic modulus in the limit state is as follows: the average diameter > directional probability entropy = abundance > fractal dimension> circularity> area.