Standard Test Method for Dispersive Characteristics of Clay Soil by Double Hydrometer

Importancia y uso:

5.1 Dispersive clays are those which normally deflocculate when exposed to water of low-salt concentration, the opposite of aggregated clays that would remain flocculated in the same soil-water system (3, 4, 7). Generally, dispersive clays are highly erosive, possibly subject to high shrink-swell potential, may have lower shear strength, and have lower permeability rates than aggregated clays.

5.2 When the percent dispersion equals 100, it indicates a completely dispersive clay-size fraction. When the percent dispersion equals 0, it indicates completely nondispersive clay-size fraction.

5.3 Available data (1) indicates that the test method has about 85 % reliance in predicting dispersive performance (85 % of dispersive clays show more than 35 % dispersion).

5.4 Since this test method may not identify all dispersive clays, design decisions based solely on this test method may not be conservative. It is often run in conjunction with the crumb test (D6572) (4, 7), the pinhole test (D4647/D4647M), or the analysis of the pore water extract (D4542) (4, 7), or combination thereof, to identify possible dispersive clay behavior.

Note 1: The quality of the result produced by this standard is dependent on the competence of the personal performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depends on many factors; Practice D3740 provides a means of evaluating some of those factors.

Subcomité:

D18.06

Referida por:

D4647_D4647M-13R20, D6572-21

Volúmen:

04.08

Número ICS:

91.100.15 (Mineral materials and products)

Palabras clave:

clays; deflocculation; dispersion; dispersive clay; erosion; gradation; hydrometer analysis; jugging; particle size; piping; sedimentation analysis;