Bingham Yield Stress Research Articles

Effect of pH on the Rheology of Marine Clay from the Site of the South Nation River, Canada, Landslide of 1971

AbstractThe pH of Na-saturated, carbonate-containing and carbonate-free Leda clay, at salinities of 2 and 10 g/liter, was decreased from pH 8 to 4 by the addition of HCl. The Bingham yield stress, as determined with a coaxial viscometer, increased in all materials as the pH decreased. Above about pH 7 the 2-g/liter materials had a lower yield stress at any water content than the 10-g/liter materials, whereas, below about pH 6.8 the yield stress of the carbonate-containing soil at a salinity of 10 g/liter was lower. For the carbonate-free material, the change occurred at about pH 6.2. The influence of salinity on the remolded shear strength of these materials was pH-dependent. A yield stress increase with decreasing pH was likely due to a change in ion saturation. The carbonate-free material exhibited a maximum yield stress at about pH 5.5–6.2, depending on salinity. The isoelectric points for oxides and clay mineral edges most probably account for the existence of the maximum.

Rheological Properties of Clay Pastes—Part III: Surface Area and Thixotropy at Liquid Limit Consistency

Investigations to correlate various rheological parameters as Bingham yield stress, thixotropic break-down at upper plastic limit consistency, cation exchange capacity, liquid limit with specific surface area (SSA) of some Indian red, black and alluvial soils have been reported. A linear relationship between liquid limit/cation exchange capacity and specific surface area was noted. The plot between the ratio of plastic index (PI) and specific surface area (SSA) against Bingham yield stress or liquid limit yielded three linear curves which indicate the texture, CH, CL and CL-ML group, of soils. The Bingham yield stress decreased while the liquid limit increased with increasing ratios of PI/SSA. The two curves of identical slopes representing CH and CL group of soils were characteristic of (1) plastic soils having liquid limit above 50, containing expanding group of clay minerals and (2) lean plastic soils of liquid limit below 50, containing a mixture of kaolinite and mica group of clay minerals.

Acoustic fluidization and the scale dependence of impact crater morphology

A phenomenological Bingham plastic model has previously been shown to provide an adequate description of the collapse of impact craters. This paper demonstrates that the Bingham parameters may be derived from a model in which acoustic energy generated during excavation fluidizes the rock debris surrounding the crater. Experimental support for the theoretical flow law is presented. Although the Bingham yield stress cannot be computed without detailed knowledge of the initial acoustic field, the Bingham viscosity is derived from a simple argument which shows that it increases as the 3/2 power of crater diameter, consistent with observation. Crater collapse may occur in material with internal dissipation Q as low as 100, comparable to laboratory observations of dissipation in granular materials. Crater collapse thus does not require that the acoustic field be regenerated during flow.

A schematic model of crater modification by gravity

Models are proposed to account for the formation of slump terraces, central peaks, peak rings, and concentric rings in large impact structures. Crater slumping and central peak formation is attributed to the process of acoustic fluidization, which endows a volume of the target surrounding the crater with a Bingham plastic rheology for a short time after the impact. The parameters of this Bingham plastic model are remarkably constant throughout the solar system the Bingham yield stress ranges from a maximum of 80 bars on Mercury to a minimum of 7 bars on Callisto. The Bingham viscosity is between 109 and 1010 P at the onset of central peak formation for all bodies studied, although it appears to rise to 1011 P as crater diameter grows to a few hundred kilometers. Asymmetric (or scarp‐bounded) concentric rings are due to a fundamentally different process. They form when the target planet's lithosphere fractures under stresses imposed by the flow of the asthenosphere toward the transient crater cavity. Lithosphere yield strengths of less than a few hundred bars are implied by observed ring development on the moon and Callisto.

Rheological Properties of Clay Pastes—Part II: Thixotropic Co-efficient at Liquid Limit Consistency

Studies on the application of rheological properties of clay pastes from red, black and alluvial clays for the determination of liquid limit have been further extended to determine the thixotropic coefficient of various clays at liquid limit consistency. The thixotropic co-efficient at liquid limit consistency, irrespective of clay mineral composition varies in a narrow range of 0.7 to 1.50. At this consistency, the Bingham yield stress and thixotropic area also vary in a narrow range. The plot between thixotropic co-efficient and moisture content at liquid limit of various clays holds two linear relationships: (i) for plastic clays having liquid limit above 50 and (ii) for lean clays having liquid limit below 50±2. The small variations occurring in thixo-tropic co-efficient at liquid limit consistency have been attributed to the nature of exchangeable and adsorbed ions, organic matter, non-clay fractions, surface roughness on sand and silt particles etc.

Particle interactions in aqueous kaolinite suspensions: I. Effect of pH and electrolyte upon the mode of particle interaction in homoionic sodium kaolinite suspensions

Flow curves of dilute homoionic sodium kaolinite suspensions have been measured as a function of pH and electrolyte concentration. The changes in Bingham yield stress have been shown to be entirely in accord with the Schofield-van Olphen model of particle interactions, and it has been possible to elucidate the conditions under which edge-face, edge-edge, and face-face coagulated structures exist. The results have also enabled the isoelectric point of the edge surface of this kaolinite sample to be located at pH 7.3 ± 0.2. The electrolyte concentration required to develop the edge-edge structure fully increases as the edge surface potential increases on either side of the edge isoelectric point; the results are in accord with the DLVO theory of colloidal stability. Comparison of the effects of 1:1, 1:2, 2:2, and 2:1 electrolytes on the Bingham yield stress suggests that the anionic species may be the more important in converting edge-face structures into the edge-edge form at low pH values. The effect of pH and electrolyte concentration on the plastic viscosity is also discussed in terms of the electrical double layers at the kaolinite/water interfaces.

Particle interactions in aqueous kaolinite suspensions: III. Sedimentation volumes

Sediment volumes of suspensions of homoionic “Al-free” Na kaolinite, Standard Porcelain, and a natural kaolinite sample have been followed as a function of pH and NaCl concentration. The addition of NaCl decreases the sediment volume at low pH values and increases it at high. The results are interpreted in terms of the effect of the electrolyte upon the density of packing of particles within flocs and average floc size. It is suggested that the Bingham yield stress is a more sensitive measure of particle-particle interactions than the sedimentation volume.

Particle interactions in aqueous kaolinite suspensions: II. Comparison of some laboratory and commercial kaolinite samples

Flow curves of dilute suspensions of a natural kaolinite sample and two commercial kaolinite samples have been measured as a function of pH and NaCl concentration. The results have been compared with five specially prepared batches of sodium kaolinite. Two of the untreated and two treated samples were found to be contaminated with a specifically adsorbed aluminum species, and they also had edge isoelectric points lower than the specially prepared Na kaolinites which were “aluminum free.” Possible reasons for this shift are discussed and comments are made about the preparation process. The effect of NaCl and pH upon the Bingham yield stress of the kaolinite samples can be explained in terms of the modes of particle interaction discussed previously in a detailed study of the “Al-free” Na kaolinite, but the pH values and added NaCl concentrations at which edge-edge interactions are fully developed vary according to the edge isoelectric point and degree of contamination of the clay with soluble salts. Finally, the results of this study are compared with those of others.

Rheology of concentrated suspensions of spheres. II. Suspensions agglomerated by an immiscible second liquid

Small amounts of a second immiscible liquid, water, were introduced into suspensions of glass beads (untreated or surface treated with dimethyldichlorosilane) in liquid polybutadiene. Water formed liquid bridges between the particles and caused the suspensions containing untreated beads to agglomerate. These large agglomerates changed the flow behavior from Newtonian to pseudoplastic. The extrapolated Bingham yield stress went through a maximum as the amount of water increased. Surfactants first decrease the pseudoplastic behavior and then, at higher concentrations, surfactants cause the suspensions to become Newtonian in behavior. A theory was developed in an attempt to explain the experimental results. The theory predicts pseudoplastic flow behavior for agglomerated suspensions, but the quantitative correlation between theory and experiment is not satisfactory.

Structure of thixotropic suspensions in shear flow: I. Mechanical properties

A theory for the steady state viscosity η of thixotropic clay-water suspensions is given. The numerical results of this analysis can be approximated by u + u2/10 = K/γ̇ where u = (ηr − 1)/C, γ̇ is the shear rate, η∞ is the viscosity for γ̇ → ∞, ηr =η/η∞, and K and C are parameters depending on concentration and temperature. For large shear rates this expression reduces to the Bingham behavior ηr = 1 + τ0/η∞γ̇, where τ0 is the Bingham yield stress. Experiments on a Wyoming bentonite at various concentrations and temperatures give good agreement with the theoretically predicted behavior. The comparison of experimental and analytical results yields the cohesive force per particle and the ratio of the major and minor dimensions of the bentonite particles.