Study on the mechanical properties and microscopic mechanism of structural clay of zhanjiang formation under the action of vibration disturbance
[Objective]In order to study the mechanical properties and microstructure evolution mechanism of Zhanjiang Forma-tion structural clay under vibration disturbance,[Methods]using the electric frequency modulation shaking table to apply differ-ent vibration frequency and vibration time to the undisturbed soil,the clay samples with different disturbance degree were pre-pared.The unconfined compressive strength test and electron microscope scanning(SEM)test were carried out to obtain the me-chanical characteristics and micro-damage law of the soil.[Results]The result show that after vibration disturbance,the uncon-fined compressive strength of soil decreases significantly,the stress-strain curve of the sample is strain softening type,and the failure strain of disturbed soil decreases with the increase of vibration time and vibration frequency,and are larger than the failure strain of the undisturbed soil.When the vibration frequency is constant,the overall disturbance degree increases with the exten-sion of vibration time,and the disturbance degree increases faster in the previous period and slows down gradually in the later pe-riod.When the vibration frequency is 20 Hz,after 60 min,the unconfined compressive strength of the sample has no significant change,and the samples with vibration frequency of 35 Hz and 50 Hz do not have similar result.For the curves with different vibration frequencies,the curve moves up as a whole with the increase of vibration frequency,and the relationship between fractal dimension,pore probability entropy and disturbance degree is positive correlation,and the relationship between area probability distribution index and disturbance degree is negative correlation.After disturbance,the pore surface morphology is more complex,the degree of distortion is higher,the pore area increases,and the directional arrangement of pores tends to be more disordered.[Conclusion]The result show that the soil strength of Zhanjiang Formation structural clay decreases significantly after experiencing vibration disturbance.Through the scanning electron microscope test,it is found that the essence of the strength decline is the change of the microstructure of the soil sample,and the vibration disturbance makes the clay microstructure change from the honeycomb-compact flocculation composite structure to the loose flocculation structure.The contact mode and arrange-ment rules between clay particle units have changed,and the main factor of soil strength damage is the fracture of colloid bond between clay particles.The research result can provide a theoretical basis for explaining the macroscopic phenomena in the process of soil disturbance damage.
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