Abstract:

It is necessary for underground backfill to concentrate the tailing slurry at a higher level.Polyacrylamide which can effectively accelerate tailings sentiment and reduce the overflow sands，is an ordinary additive material in this process.However，flocculants-sedimentation always results in lower underflow density which is unreliable and is useless for backfilling.Still，research has shown that proper settling disturbance is beneficial to increase the density of settling underflow，such as deep cone thickener.The interaction between disturbance rake and flocs in a cone thickener is very complex.However，the core idea is that the disturbance process which destroys the water consolidation process of flocs.Research results at home and abroad has shown that the result of flow density by dynamic settling is much higher than that by natural flocculation settling.In this research direction，many scholars have gained some valuable experience，such as using computational fluid dynamics （CTD） to analyze the adsorption process of flocculants and analyze the shear effect to the activity of flocculants.Also，some used dynamic flocculation settling and rheological parameters to analyze the pressure rake of deep cone thickener，such as analysis about pressure rake in flocculation settling.The research process and conclusions are very helpful，but the dynamic effect of disturbed rake in flocculation settling process and its causation of concentration need to be further studied.In order to find out the internal mechanism of the dynamic settlement，some comparative experiments were carried out in this paper.It is shown that，a low frequency disturbance by the disturbed rake，the settling rate is significantly improved，with an increase rate of 24%，and the underflow density were greatly increase which up to 10% comparing to corresponding values in the static flocculants-settlement.Through the analysis，the reason of this results mostly attribute to three factors，that are reshaping-effect，scattering-effect and channel-effect.Reshaping-effect is that the disturbed rake continuously changes the spatial geometry shape of flocs in the settling process，promotes the wrapped water outflowing therefore increasing the settling rate.Scattering-effect is that the disturbed rake forms a velocity field in the settling space，which changes the settling path of flocs，promotes the reshaping-effect and discharge the micro-excess pore water in the flocs，thus affecting the settling rate.Channel-effect is that the small displacement of the rake makes it form a water micro passage behind the rake rotation path，which making excess pore water flow out，reducing the porosity in the Compaction Zone and increasing the underflow concentration.In this paper，the microscopic analysis of disturbing flocculation settling is focused on and three factors are analyzed and formed for reference.

Key words: tailings, disturbed flocculants-sedimentation, excess pore water pressure, flocs, underflow density, flocculation and settlement mechanism