Kayli DeCocker

Granular rheology is of interest in many geophysical and industrial applications that require precise handling of particulate materials, including conveying, dosing, spreading, compaction, and other operations. The capability to handle dense flows is important for process throughput and efficiency. In this context, we explore oscillatory rheometry for dense granular flow using a chute-flow rheometer (CFR) having multimodal sensing capability. The CFR applies oscillatory shear in a Couette gap with measurements of torque, wall pressure, and axial flow. The resulting cyclic data were deconstructed into elastic and viscous components using Fourier transforms. Torque data were normalized to the active mass of granular material in the CFR, converted to specific torque and shear stress, and analyzed using Lissajous–Bowditch (LJB) plots. Viscoelastic crossovers were observed at relatively low shear rates consistent with quasistatic (i.e., friction-like) flows. At higher shear rates, secondary loops were observed in elastic (γ˙,τ) LJB plots, consistent with transition to dense inertial (i.e., fluid-like) flow. These rheological markers are discussed in terms of dense flow transitions. Further analysis considered inertial number scaling in the μ(I) granular rheology, comparing specific torque with the conventional definition using pressure and bulk density. Finally, a contour diagram summarizes the coupling of shear and normal forces in the CFR, where the wall pressure sensor detects the first normal force and the second normal force is in the direction of axial flow. The results suggest characterization criteria that are relevant to managing dense granular flows in quasistatic and dense inertial regimes.

Ultraviolet light cured-in-place pipe is a popular trenchless rehabilitation technology used to repair existing buried pipelines without soil excavation. A polymer composite liner is manufactured directly in the field. After curing is complete, the new liner is placed in service to convey flowing water. Long-term water exposure has the potential to degrade the fiber reinforced cured-in-place pipe liners. Like other composites, liner hygrothermal stability could be a major challenge, especially for undercured materials. The objective of this study was to investigate the effect of aggressive environmental conditions such as water, salt solution, and simulated concrete pore solution at 50℃ on cured-in-place pipe liner mechanical and thermo-mechanical performance. Liners were exposed to aqueous solutions ranging from a typical exposure environment to a very aggressive alkaline environment. Cured-in-place pipe liner samples were collected from New York storm sewer installation sites. Specimens were assessed for the degree of curing as determined by differential scanning calorimetry and TGA. Samples were then immersed in aforementioned solutions for investigating the stability of the liners as a function of degree of cure. Both interlaminar shear strength and thermo-mechanical properties significantly differed based on the degree of cure. Cured-in-place pipe liner mechanical and thermo-mechanical properties were significantly impacted by water, salt, and pore solutions exposure. Long-term exposure to salt and alkaline environments may have a detrimental effect on the performance of cured-in-place pipe liners and desires additional scrutiny.