Boundary Shear Stress Measurement by Preston Tube

by Malcolm Hollick,


Serial Information: Journal of the Hydraulics Division, 1976, Vol. 102, Issue 7, Pg. 1053-1057


Document Type: Journal Paper

Abstract:

This work confirmed the possibility of using the Preston tube technique on sand roughened boundaries but emphasized certain problems, particularly those related to obtaining a satisfactory theoretical calibration. The main conclusions were that: 1. A small plate close to the nose of the Preston tube can increase the accuracy, particularly where the tube diameter is not large than the grains; 2. the effective boundary roughness, Ks, is between the mean and maximum grain size unless the sand is very closely graded; and 3. the value of z may vary with position of the probe on the boundary and cannot be predicted, which results in uncertain stress readings.



Subject Headings: Shear stress | Boundary shear | Domain boundary | Sandy soils | Grain (material) | Plates | Calibration | Probe instruments

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