Experimental Study On Influencing Factors Of Settling Velocity Of Soil Particles

The particle composition of soil has a significant effect on the engineering properties of soil.The existing specifications for geotechnical tests use the settlement analysis method based on Stokes settlement rate formula to test the particle size composition of fine particles in soil while the Stokes theory assumes that the particle is an ideal sphere,the surface of the particle does not carry charge and so on.These often do not conform to the actual conditions of soil particles.For example,clay mineral particles are mostly flake and there is a large density of unsaturated charge on the surface.The sedimentation rate of this kind of particles in aqueous solution is quite different from that of the ideal sphere assumed by Stokes,which leads to the error in the measurement of soil particle size composition by settlement analysis method.This error can affect the tester's understanding and judgment of the basic characteristics of soil,such as the settlement rate of non-spherical or even flake mineral particles is small,which leads to the overestimation of clay content in soil samples.Such misjudgment can prevent scholars from exploring the physical mechanism and law of particle size distribution affecting soil strength and deformation.It is not conducive to the selection of relevant engineering and technical schemes,and even affects the reliability of engineering and technical scheme design.Therefore,based on the laser scattering method whose measurement accuracy is not affected by the particle settlement rate,the settlement analysis method is compared and analyzed using artificial soil and natural soil respectively,and the influencing factors of particle settlement rate are discussed.In view of the factors affecting the sedimentation rate of the particles mentioned above,the sedimentation rate experiments were carried out by self-made experimental equipment to explore the mechanism and law of the effects of mineral composition,particle size,particle concentration,ion concentration and other factors on the sedimentation rate of particles.The sedimentation potential test was carried out by self-made test equipment to explore the mechanism and law of the influence of mineral composition,particle size,particle concentration,ion concentration and other factors on particle sedimentation potential and sedimentation potential.The main research work and achievements of this paper are as follows:i.Taking two kinds of artificial clay mineral particles,two kinds of artificial non-clay mineral particles and natural soils in four areas as test objects,the comparative tests and analysis of settlement analysis method and laser scattering method were carried out.Because the experimental results of laser scattering method are not affected by particle sedimentation rate,this paper studies the influencing factors and their mechanism of the influence of particle sedimentation rate based on the experimental results of laser scattering method.The comparative experimental results show that the errors caused by the sedimentation analysis of different mineral particles are different.The greater the surface activity of mineral particles,or the more the shape deviates from the sphere,the greater the error of particle size composition measured by sedimentation analysis.ii.Based on the comparative test results of settlement analysis method and laser scattering method,the method of correcting the error of settlement analysis method is explored.By using the correction methods of "primary correction" and "secondary correction",the correction effect is good.iii.The sedimentation rate test was carried out by self-made test equipment.The results showed that the sedimentation rate of non-clay mineral particles was positively correlated with particle size and negatively correlated with particle concentration and ion concentration.The sedimentation rate of clay mineral particles increases with the increase of particle size and particle concentration,while increases at first and then decreases with the increase of ion concentration.When equivalent grain size is the same,the sedimentation rate of clay mineral particles is much lower than that of non-clay mineral particles.iv.The sedimentation potential test was carried out by self-made test equipment.The results showed that the particle sedimentation potential was positively correlated with suspension depth and particle concentration,and negatively correlated with sedimentation duration and ion concentration.The sedimentation potential of non-clay mineral particles is negatively correlated with the particle size,and the sedimentation potential of clay mineral particles is positively correlated with the particle size.Under the same settling environment,the settling potential of clay mineral particles is larger than that of non-clay mineral particles.