Analysis of piezocone dissipation data using dislocation methods

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Abstract

The theory of a moving point dislocation is applied to the rational determination of permeability and consolidation coefficients from piezocone-sounding data. Motion of the process zone in following the penetrometer tip is shown to result in important differences in behavior between static and undrained analogs to penetration. A distinction is drawn between pressure buildup and postarrest dissipation behaviors recorded both at the tip and along the shaft. Tip pressures are shown to become steady within approximately 1 s following drivage initiation at a standard rate of 2 cm/s. Shaft pressures within 10 radii of the tip equilibrate within 10 s. Postarrest pressure dissipation at the tip enables consolidation coefficient, c, to be determined independently. Nonuniqueness in pressure-dissipation response along the shaft is shown to preclude independent determination of consolidation behavior for consolidation coefficients less than about 20 cm2/s, under standard penetration. Hydraulic conductivities, k, are directly evaluated from induced pore pressure magnitudes recorded either at the tip or along the shaft, given a priori knowledge of consolidation coefficient, c. Piezocone-derived magnitudes of consolidation coefficient enable conductivities to be determined independently of laboratory or material-specific empirical determinations. Relationships are developed for net cone end bearing (qn) as a linear function of elastic parameters and for pore pressure ratio (Bq). Pore pressure ratio is shown to be an insensitive index in low c soils. Results from well-documented field investigations in both normally consolidated and overconsolidated materials are used to independently establish the applicability of the proposed parameter determination techniques. Satisfactory correspondence is obtained.

Original languageEnglish (US)
Pages (from-to)1601-1623
Number of pages23
JournalJournal of Geotechnical Engineering
Volume119
Issue number10
DOIs
StatePublished - Jul 1993

All Science Journal Classification (ASJC) codes

  • Environmental Science(all)
  • Earth and Planetary Sciences(all)

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