Study On The Microscopic Mechanism Of Cementation And Capillarity Between Spherical Particles

For geotechnical engineering,the cementation involves issues such as cultural relic restoration and soil slope reinforcement,while the capillarity involves disaster prevention of unsaturated soil slopes.These engineering problems can be attributed to key scientific issues such as the cemented and liquid ridge interactions between unsaturated soil particles,which have a significant impact on the mechanical properties of unsaturated soil.In order to avoid the uncertainty of particle shape in research,the soil particles with different shapes are simplified into homogeneous spherical particles.To explore inter particle cementation,the consolidated undrained triaxial test and cemented unit mechanical test are carried out for granular materials with different cementation content,then the law of macroscopic and mesoscopic specimens is qualitatively and jointly analyzed.To explore the capillarity between particles,the effects of tensile speed,liquid volume,particle size ratio,and proximity of upper particles on the mechanical parameters of the funicular bridge are studied respectively,then the coalescence and rupture criterion of the funicular bridge are analyzed;the separation of the pendular bridge with a constant volume is numerically studied using Surface Evolver software;based on the Young-Laplace equation and the "Gorge" method,the mechanical and water retention characteristics of the pendular bridge with a constant suction are calculated analytically.This article provides a calculation approach for the required parameters for the discrete element method of macroscopic cemented or unsaturated granular aggregates.The main conclusions are as follows:(1)With cementation content increasing,the peak strength and shear strength parameters of the cemented granular specimens increase,and the strength growth rate shows a nonlinear growth trend.With confining pressure increasing,the strengthening effect of solid matrix on cemented granular materials gradually decreases.(2)The tensile and shear peak force of the cemented unit is proportional to the particlematrix contact area.Increasing cementation content causes the shear strength parameters of the cemented specimens increase.Compared to the tensile failure resistance,increasing cementation content is beneficial to improving the shear failure resistance of cementitious granular materials.(3)The pinning effect of the contact angle is determined by the liquid volume and solidliquid contact angle.The backward section of the initial contact angle corresponds to the rising section of the liquid bridge force-separation distance curve.The effect of tensile speed on liquid bridge force and rupture distance is positively correlated with liquid viscosity.The coalescence of liquid bridge leads to an increase in the rupture distance.The rupture distance of the funicular bridge is positively correlated with the liquid volume.(4)The pinning effect of the solid-liquid contact angle causes the rising section of the forceseparation distance test curve.The test curve of the pendular bridge is reproduced using Surface Evolver software.The gravity causes the liquid bridge force to increase and rupture distance to decrease.The larger the solid-liquid contact angle of the liquid,the more obvious the effect of gravity on liquid bridge force and rupture distance.(5)The "Gorge" method is more accurate in calculating the liquid bridge force of the liquid bridge between micron-sized particles.The rupture distance is negatively correlated with the suction.The water retention characteristic between two particles is positively correlated with particle size,particle size ratio and liquid-gas surface tension,but negatively correlated with suction and solid-liquid contact angle.