The Dilemma of Measuring Small Pressure Changes in a Settling Tube

by Tatsuaki Nakato, Univ of Iowa, Iowa City, United States,
Roger W. Lehman, Univ of Iowa, Iowa City, United States,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering


A compact settling tube was developed to determine fall-velocity and particle-size frequency distributions and specific gravities of sand-range sediment samples by means of direct measurements of temporal pressure records. The apparatus measures the hydrostatic pressure of the sediment-water mixture at a low point of the settling tube as sediment particles settle past that point following the release of a sediment sample at the top of the settling tube. The measured time history of pressure variations provides a frequency distribution of fall velocities of different particle sizes. The fall-velocity distribution then is used to obtain the spherically-equivalent particle-size frequency distribution.

Subject Headings: Pressure measurement | Pressure distribution | Particle size distribution | Frequency distribution | Velocity distribution | Sediment | Particle velocity | Soil pressure

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