Macroscopic models for the uniaxial consolidation of strong colloidal gels typically characterise the compressive strength of the particulate network in terms of the compressive yield stress P y ( ϕ ) or uniaxial elastic modulus K ′ ( ϕ ). Almost all industrial applications involve multi-dimensional (MD) configurations with arbitrary tensorial stress states, and it is unclear how to generalise these 1D constitutive models to MD consolidation. Several studies have attempted to extend these 1D constitutive models to MD by assuming either isotropic consolidation or zero Poisson’s ratio, but the validity of these assumptions is currently unknown. Lacking is a validated tensorial rheology for the consolidation of strong colloidal gels that is capable of predicting the consolidation of these materials. One step toward the development of such tensorial rheology is the consideration of normal stress differences (NSDs) during uniaxial consolidation. Thus, a tensorial constitutive model for the consolidation of colloidal gels cannot be developed without accounting for these NSDs. We address this problem by performing discrete element model (DEM) simulations of the uniaxial consolidation of a two-dimensional (2D) strong colloidal gel and investigate evolution of the tensorial stress state during consolidation. We show that during consolidation, the Poisson ratio increases from zero near the gel point to almost unity near close-packing and uncover the particle-scale mechanisms that underpin these observations. These results provide the first steps toward a complete tensorial rheology of colloidal gels that is capable of resolving the evolution of these complex materials under superposed differential compression and shear. Graphical abstract

中文翻译：

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强胶体凝胶固结中的法向应力差异

强胶体凝胶单轴固结的宏观模型通常根据压缩屈服应力 P y ( ϕ ) 或单轴弹性模量 K ′ ( ϕ ) 来表征颗粒网络的压缩强度。几乎所有的工业应用都涉及具有任意张量应力状态的多维 (MD) 配置，目前尚不清楚如何将这些一维本构模型推广到 MD 固结。一些研究试图通过假设各向同性固结或零泊松比将这些一维本构模型扩展到 MD，但这些假设的有效性目前未知。缺乏一种经过验证的用于强胶体凝胶固结的张量流变学，它能够预测这些材料的固结。发展这种张量流变学的一个步骤是考虑单轴固结过程中的法向应力差 (NSD)。因此，如果不考虑这些 NSD，就无法开发用于胶体凝胶固结的张量本构模型。我们通过对二维 (2D) 强胶体凝胶的单轴固结进行离散元模型 (DEM) 模拟并研究固结过程中张应力状态的演变来解决这个问题。我们表明，在固结过程中，泊松比从凝胶点附近的零增加到紧密堆积附近的几乎统一，并揭示了支持这些观察的粒子尺度机制。这些结果为胶体凝胶的完整张量流变学提供了第一步，该凝胶能够解决这些复杂材料在叠加的不同压缩和剪切下的演变。图形概要