关键词: 盐渍土, 微观孔隙, 电镜扫描, 动三轴试验, 循环应力, 振动频率

Abstract:

Taking saline soil in the Qarhan area as the research object， using Scanning Electron Microscope （SEM） equipment and particle pore and crack image recognition and analysis system （PCAS）， microscopic quantitative identification and structural analysis are carried out. Applying image segmentation principle and fractal theory to study the microstructure of saline soil under traffic cyclic loading， the characteristics of pore distribution and its microscopic mechanism under different cyclic stress ratios and different frequencies are discussed. The results show that the cyclic stress ratio R increases from 0.375 to 0.75， the critical failure dynamic strain increases from 2.32% to 3.17%， and the number of dynamic load cycles decreases accordingly. The vibration frequency f increases from 0.5 Hz to 2.0 Hz， the critical failure dynamic strain reduces from 2.82% to 2.48%， and the number of dynamic load cycles increases correspondingly. The microscopic parameters of saline soil increase with the cyclic stress ratio， fractal dimension value of pore scale D_v increases by 0.12， probability entropy H_m decreases by 0.017， fractal of the morphology of pores D decreases by 0.27， average shape coefficient F increases by 0.14； the microscopic parameters increase with the vibration frequency， D_v increases by 0.014， H_m decreases by 0.002， D changes by 0.06， average shape coefficient F changes by 0.003. Under dynamic loading， the pore space arrangement of sample is consistent with the fold and drum deformation of the macroscopic soil. Based on the comparison of microstructure parameters about the unloaded sample and loaded sample， the interaction mechanism between cyclic stress ratio and vibration frequency on the saline soil microscopic pore characteristics and macroscopic deformation has systematically analyzed.

Key words: saline soil, micro-pore structure, Scanning Electron Microscope （SEM）, dynamic tri-axial test, cyclic stress, vibration frequency