Presented by Muhammad Rizwan Riaz

2. IDENTIFICATION OF
DISPERSIVE SOILS
(Foundation Engineering-I)
Presented by:
Muhammad Rizwan Riaz 2011-MS-CES-01
Omer Abrar 2011-MS-CES-06

3. CONTENTS
The discussion is divided into the following sections :
• Introduction
• Dispersion Phenomenon
• Problems caused by Dispersive Soils
• Failure Examples
• Identification

4. Dispersive Soils
• Soils that are dislodged easily and rapidly in
flowing water are called dispersive soils
• Highly susceptible to erosion and containing
high percentage of exchangeable sodium ions
• Also called Sodic Soils
• Disperse into basic particles (sand, silt and clay),
even in still water

5. Different Properties
• Appear to ‘dissolve’ in water
• Results in cloudy ring in fresh water
• Structurally unstable
• Responsible for tunnel erosion

6. Dispersive Soils

7. Dispersive Soils

8. Dispersive Clays vs Ordinary
Clays
• Principle difference is the nature of the
cations in the pore water of the clay mass
• Dispersive clays have an excess of sodium
(Na+) cations
• Ordinary clays are having excess potassium,
magnesium or calcium cations. (K+, Mg2+,
Ca2+)

9. Dispersion Phenomenon

10. Dispersion Phenomenon
Weak attraction due
to distance
Clay
Particles
Strong Attraction

11. Dispersion Phenomenon

12. Problems Caused by Dispersive
Soils
• Surface erosion
• Tunnel Formation
• Gully formation
• Sinkholes
• High Suspended Sediment Loads

13. Dispersive Soil Problems

14. Surface Erosion

15. Tunnels and Sinkholes

16. Gully Formation

17. Turbid Water Bodies

18. Failure Example

19. Failure Example

20. Identification of Dispersive Soils
• Visual Identification
• Identification Test
– Crumb Test ASTM D 6572-06
– Pinhole Test ASTM D 4647-93
– Double Hydrometer Test ASTM D 4221-99
– Chemical Test

21. VISUAL IDENTIFICATION
Dribble Pattern Muddy dams
Pocketing

22. CRUMB TEST
(ASTM D 6572-06)
• Was developed as a simple procedure to
identify dispersive soils’ behaviour in
field
• Now a days, is also performed in
laboratory as a standard test

23. Test Procedure
• It consists of either preparing a cubical
specimen of about 15mm size at natural
moisture content or selecting a soil crumb at
natural water content of about equal volume
• Specimen is carefully placed in 250mL of
distilled water
• With the passage of time, the tendency of
the colloidal size particles to deflocculate
and go into suspension is observed

24. Test Results
• Results are interpreted after 1 hour and four
grades of reaction are possible
– No Reaction
– Slight Reaction
– Moderate Reaction
– Strong Reaction

25. Non-Dispersive Slightly-Dispersive Dispersive Highly-Dispersive
Discoloration in
Water remains clear Discoloration and Discoloration and
surrounding particles or
though particles may cloudiness surround cloudiness surround
distinct cloudiness
crumble. most or all particles. throughout, extending
surrounding some.
vertically throughout
Boundary of crumbs Boundary of crumbs Boundary of crumbs not
most or all water
clearly defined vaguely defined. able to be defined.

26. PINHOLE TEST
(ASTM D 4647-93)
• This method presents a direct and
qualitative measurement of dispersibility
and consequent colloidal erodobility of clay
soils by causing water to flow through a
small hole punched in a soil specimen.

27. Test Procedure
• The test method is started with distilled water flowing
horizontally under a hydraulic head of 50 mm (2 in.) through a
1.0-mm (0.04-in.) diameter hole punched in the soil specimen.
The nature of the solution emerging from the specimen under
the initial 50-mm (2-in.) head provides the principle
differentiation between dispersive and nondispersive clays.
Flow from dispersive clays will be distinctly dark and the hole
through the specimen will enlarge rapidly, with a resultant
increase in the flow rate. Flow from slightly to moderately
dispersive clays will be slightly dark with a constant hole size
and flow rate. Flow from nondispersive clays will be
completely clear with no measurable increase in the hole size.

28. Test Apparatus

29. Test Apparatus

30. Test Results
Test results are evaluated from
– The appearance of the flowing solution emerging
from the specimen
– The rate of flow
– The final size of the hole through the specimen.
These observations provide the basis for
classifying the soil specimen.

31. Test Results

32. Tested Sample

33. DOUBLE HYDROMETER
TEST (ASTM D 4221-99)
• This test method, when used in conjunction
with standard hydrometer test method D422
on a duplicate soil sample, provides an
indication of natural dispersive
characteristics of clay soils.

34. Test procedure
In this method, 2 hydrometer tests are
performed
1. Standard Hydrometer Test
2. Hydrometer Test with no mechanical
agitation nor the chemical dispertant

35. Test Results

36. Chemical Test
• A sample of pore water is extracted from a
saturated slurry of a soil sample and analysed
for cations
• Based on field performance, a soil’s total salt
content and the percentage of the cations i.e.
Sodium, are used to categorize the soil’s
dispersive characteristics.
% Sodium = Na(100) / TDS
Where TDS = Ca + Mg + Na + K

37. Test Results

38. Test Results

39. Refrences
• ASTM D6572-06- Standard test method for determining dispersive
characteristics of clayey soil by crumb test
• ASTM D4647-93- Standard test method for identification and
classification of dispersive clays soil by pinhole test
• ASTM D4221-99- Standard test method for dispersive characteristics
of clay soil by double hydrometer test
• C.A. Vacher et al, (June 2004), ‘Identification and management of
dispersive mine spoils’, Australian center for mining environmental
research, Australia.
• Stephen davies and Alison Lacey, (Nov 2009), ‘Identifying Dispersive
Soils’, Department of agriculture and food, Australia.
• T. S. Umesh et al, (June 2011), ‘Characterization of dispersive soils’,
scientific research journal.

40. References
• Mahabir Dixit and S. L. Gupta, (Oct 2011), ‘problems in
characterization and identification of dispersive soils’, international
journal of earth sciences and engineering.
• Sameer vyas et al, (Oct 2011), ‘stabilization of dispersive soils by
blending polymers’, international journal of earth sciences and
engineering.
• Edgar H. Nelson, (Feb, 1991), ‘Soil mechanics note no. 13’, soil
conservation service, united states department of agriculture.