充填料浆中气泡作用机理及其流变特性演变规律

Mechanism of bubble action in backfill slurry and the evolution of its rheological properties

充填料浆是由固-液-气三相组成的悬浮体,长期以来有关充填料浆研究重点多是固-液两相的流变特性,而气相因素对于具有复杂流变特性的料浆影响却鲜有报道。气相成分可以显著降低充填浆体的屈服应力、黏度,对于改善管道输送性能、降低管道磨损等方面具有显著优越性。首先,通过控制引气剂(TTAB)掺量调节料浆含气量,并测定充填料浆表面张力、空气体积分数、流变性能等参数,探寻料浆中气泡对其流变性能的影响规律。其次,引入毛细管力(F_(cay))、无量纲屈服应力(τ_(ref)/τy)气泡演变模型来分析料浆内气泡演变特征,以期探明气泡对料浆流变特性的作用机理。结果表明,当充填料浆含气量较低时(<12.5%),气相因素对悬浮体料浆流变特性影响甚微,而伴随含气量增加气泡对充填料浆流变特性的影响愈发显著。引气剂作用下气泡表面对料浆内细颗粒体产生斥力,降低了水泥、固废(尾砂)等细颗粒的吸附力,导致料浆屈服应力表现为递减趋势,其流动性呈现增强趋势。基于毛细管力(F_(cay))与无量纲屈服应力(τ_(ref)/τ_(y))理论分析了充填料浆不同含气量下流变特性演变机制,当含气量增加(12.5%~27.7%),料浆的表面张力、屈服应力降低,气泡挤压变形;高含气量下(接近28.6%),料浆内气泡极易破裂。另外,气泡滞留充填体内部导致强度劣化,为此就气泡对充填体力学性能影响及其解决措施开展了探索,并提出了3点有效措施。通过揭示气泡对于充填料浆流变特性影响与其演变特征规律,为高泡充填减阻减磨技术发展提供理论支撑。

Cemented paste backfill is a suspension composed of solid-liquid-gas three-phase.For a long time,the focus has been mostly on the rheological behavior of solid-liquid two-phase,while the effect of gas phase on slurry with complex rheological behavior remains obscure.The gaseous phase components can significantly reduce the yield stress and viscosity of high-concentration backfilling slurry,which plays a significant role on improving pipeline transportation per-formance and reducing pipeline wear.In order to reveal the mechanism of bubbles to its rheological properties of slurry,the gas content of slurry was controlled by adjusting the content of air entrainment agent(TTAB),and tests such as sur-face tension,air content and rheological properties were carried out to find out the influence of bubbles on the rheological behavior of slurry,and capillary force(F_(cay))and the bubble evolution model of dimensionless yield stress(τ_(ref)/τ_(y))were in-troduced to analyze the bubble evolution characteristics in the slurry and reveal the mechanism of bubbles on the rheolo-gical properties of slurry.The results showed that under the low gas content(<12.5%),the gas phase had little effect on the rheological behavior of the suspended slurry.As the increase of gas content,the effect of bubbles on the rheological behavior of backfilling slurry was immense.Under the action of the air-entraining,the bubble surface had a repulsive force on the fine particles in the slurry,and could reduce the adsorption capacity of cement and solid waste,resulting in a de-creasing trend of slurry yield stress and increasing fluidity.Based on capillary force(F_(cay))and dimensionless yield stress theory(τ_(ref)=τ_(y)),evolutional mechanism of rheological properties of slurry in different gas content was analyzed.It could be seen that as the gas content increased(12.5%-27.7%),the surface tension and yield stress of slurry decreased,and the bubble would be deformed by extrusion.When the gas content(28.6%)was high,the bubbles in the slurry were easy to burst.In addition,bubbles,retained inside the backfilling body,leading to strength degradation,so the effect of bubbles on the mechanical properties of the backfilling body and its solution were explored and three effective measures were pro-posed.By revealing the effect of bubbles on the rheological properties of suspension slurry and its evolution characterist-ics,it provides theoretical support for the development of high bubble filling,which can achieve the goal of drag reduc-tion and friction reduction.