Computation of local permeability in gap-graded granular soils

Abstract

This letter proposes semi-analytical methods to obtain the local permeability for granular soils based on indirect measurements of the local porosity profile in a large coaxial cell permeameter using spatial time domain reflectometry. The porosity profile is used to obtain the local permeability using the modified Kozeny-Carman and Katz-Thompson equations, which incorporated an effective particle diameter that accounted for particle migration within the permeameter. The profiles of the local permeability obtained from the proposed methods are compared with experimentally obtained permeability distributions using pressure measurements and flow rate. The permeabilities obtained with the proposed methods are comparable with the experimentally obtained permeabilities and are within one order of magnitude deviation, which is an acceptable range for practical applications.

The Technical Challenges for Applying Unsaturated Soil Sensors to Conduct Laboratory-Scale Seepage Experiments

“…The in/outflow of a one-dimensional soil column could be measured using versatile methods: (1) the flow rate logging using flowmeters; (2) the accumulative soil moisture discharge logging by applying conventional TDR analysis for an FRC sensor; (3) the weight logging for the entire soil column or outflow tanks using digital bench scales. The flowmeters have successfully been applied to measure in/outflow rates by many single-phase seepage experiments integrated with the TDR sensor technique in previous studies [ 19 , 20 , 21 , 28 , 83 , 84 ]. All those studies applied a high-precision electromagnetic flowmeter for flow rates logging at higher flow rates, which were generated for a single-phase flow seeping through perfectly spherical glass beads in various sizes under unconsolidated conditions.…”

“…With this theoretical development, there has been a high demand for innovative sensor techniques and soil testing methods. Those sensor techniques were designed for measuring soil suction [ 5 , 6 , 7 , 8 , 9 , 10 ], soil moisture content [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ], soil density/porosity [ 17 , 18 , 19 , 20 , 21 , 22 ], soil temperature [ 23 , 24 , 25 ], soil electrical conductivity [ 24 , 26 , 27 ], soil permeability/relative permeability [ 28 , 29 , 30 , 31 , 32 ], soil water retention curves [ 33 , 34 , 35 , 36 , 37 , 38 ], soil diffusivity [ 39 , 40 ], etc. With a blossoming development of those sensor techniques, the unsaturated soil testing methods have been simultaneously expanded from laboratory standard tests [ 32 , 38 , 41 , 42 , 43 , 44 ] to full-scale column tests with various boundary conditions [ 30 , 45 , 46 , 47 , 48 , 49...…”