Study On Seepage And Instability Characteristics Of Dry Stack Tailing Under Short-term Rainfall

Rainfall is an important factor causing the slope instability of dry-stack tailings pond.It is of great significance to study the seepage and instability characteristics of dry-stack tailings pond under rainfall to improve the design theory of dry-stack tailings pond.Firstly,the seepage characteristics of dry-stack tailings pond are studied.Based on the saturated zone-unsaturated infiltration layer model,combined with Darcy ’s law,the theoretical formula of the relationship between the thickness of the saturated zone and the thickness of the unsaturated infiltration zone during the infiltration process is derived.The theoretical model of water profile eliminates the assumption of the relationship between the thickness of the saturated zone and the thickness of the infiltration zone.On this basis,an improved Green-Ampt model considering the shape of soil water profile and the equivalent parameters of unsaturated infiltration zone is established,and the model is verified by experiments and finite element numerical simulation.Considering that the shallow transient saturated zone of slope under rainfall has an important influence on slope stability.In order to explore the evolution law of transient saturated zone of saturated-unsaturated slope under rainfall conditions,a research model of transient saturated zone of double-layer soil is established.Combined with Darcy’s law and continuity theorem,the theoretical calculation formula of pore water pressure in transient saturated zone is derived,and the distribution law of pore pressure in transient saturated zone is revealed.Based on Moore’s two-layer infiltration model,the theoretical formulas for calculating the depth of transient saturated zone and the value of positive pore pressure with rainfall infiltration time are derived,the temporal and spatial evolution law of transient saturated zone depth and the value of transient positive pore pressure during rainfall infiltration is revealed.The correctness of the above conclusions is verified by experiments and numerical simulations.In view of the instability characteristics of dry-stack tailings pond under short-time rainfall,based on the existing unsaturated slope stability theory,the contribution of matric suction to the calculation of shear strength of unsaturated soil is considered by using the extended Mohr-Coulomb failure criterion.The influence of rainfall factors such as rainfall intensity,rainfall duration and rainfall pattern on the stability of dry-stack tailings pond under the influence of transient saturated zone depth and transient pore pressure is studied,which provides reference for the stability analysis of the dam slope of the dry-stack tailings pond.