Experimental Study On Pore Change Law And Mechanism Of Loess Before And After Immersion In Weibei Area Of Shaanxi Province

In order to study the variation characteristics and mechanism of loess pores under the action of water,and to better understand the collapsibility of loess,the loess samples before and after water immersion were tested by laboratory test,scanning electron microscopy test,mercury injection test,energy spectrum analysis test and particle size analysis test.The characteristics of pores,microscopic morphology,chemical elements and particle size of undisturbed loess before and after water immersion were studied from macro and micro perspectives.The causes of pore change were analyzed and the following results were obtained:(1)The indoor consolidation test,scanning electron microscopy image analysis and mercury intrusion test were carried out on the loess samples before and after water immersion.The results show that the pore ratio and pore volume of saturated soil samples are larger than natural soil samples.According to this,it is proposed that the pore volume of loess increased after water saturation.(2)The particle characteristics of natural and saturated loess,the contact form between the particles,the degree of cementation and the pore characteristics were analyzed by scanning electron microscopy images.According to the energy spectrum analysis test and the particle size analysis test,the chemical elements of the soil skeleton particles and crumb particles(cement)before and after the water immersion and the variation of the particle size and specific surface area of the soil particles were analyzed.(3)Based on the microscopic test results,the mechanism of pore change after immersion was analyzed.The increase in loess pores is due to the wetting of water film and the dissolution of water.The test results show that the dissolution of water makes the surface of the soil particles rough,and the surface is covered with loosely distributed debris particles,which form more tiny pores;the dissolution of water and the wetting of water film make the granules(agglomerates)of the soil are dispersed and decomposed into small particles,resulting in a decrease in particle size and an increase in the specific surface area of the soil particles.