Streaming Potential In Loess Medium And Its Preliminary Application

The research indicates that the instability of loess geological slope in northwest area of China is mainly caused by rainfall.In the process of rainwater infiltration from the loess surface,the streaming potential will be generated along the flow path.The flow potential is related to the porosity and permeability of loess.With the increase of rainwater infiltration in the loess,the bulk density of the loess medium increases and its sliding resistance decreases,which may lead to the instability failure of the loess slope.The relationship between the flow potential of porous media and the permeability of loess column is studied in this paper.Research on microscopic scales of electrolyte fluid when flowing through the loess column flow potential causes and influence factors of loess column under different working conditions,to carry out potential relationship between permeability coefficient and flow experiment,build the flow potential correlation of soil slope stability coefficient under theoretical formula,finally told by streaming potential method of loess landslide forecast rainfall conditions.The main work is as follows:Based on the double electric layer Stern model,the variation law and distribution law of ion potential in the double electric layer of sand particles were studied,and the pores between sand particles were simplified as capillary bundles to explore the mechanism and influencing factors of the flow potential when the fluid moved in the pore medium.Under the interaction of force field and electric field,the relationship between the flow potential at both ends of porous media and Darcy seepage movement is derived.Based on this,the relationship between the permeability coefficient of loess column and the flow potential is established.At the same time,the experimental study of flow potential and permeability coefficient under different conditions of water infiltration in unsaturated loess column was carried out.The permeability coefficient of the loess column is calculated by collecting the water permeability in a period of time,and the flow potential at both ends of the loess column is monitored by a multimeter.By changing the length of the loess column,the cross-sectional area of the loess column and the water pressure at both ends of the loess column,the variation rule of the flowing electric potential of the loess column under different conditions and the relationship between the flowing electric potential and the permeability coefficient of the loess column were explored.It is found that the permeability coefficient of loess column increases with the increase of the flow potential,and there is a good consistency between the two.by comparing with the theoretical results,the theoretical formula between the flow potential and the permeability coefficient of loess column is verified.Based on the improved Green-Ampt model,the motion equation and infiltration law of rainwater in loess medium are analyzed.The stability of a particular shallow loess slope is analyzed when the wetting front is taken as the failure surface of the loess slope.The permeability coefficient of soil is calculated by the flow potential,and then the permeability coefficient is applied to the calculation of stability coefficient of soil.It is found that the larger the flowing electric potential of loess medium is,the larger the permeability coefficient of soil is,the larger the spreading velocity of soil wetting front is,and the lower the stability coefficient of shallow loess slope is.It is preliminarily determined that the occurrence of slope instability can be judged by the monitoring of current potential.