Civil engineer guide to fighting positions, shelters, obstacles

AFH 10-222 Volume 14 1 August 2008 153
A3.3.9. Ribbon Test. This test is also performed only on material passing the
No. 40 sieve. A representative portion of the sample is mixed with water until
it can be molded or shaped without sticking to the fingers. Form a roll of soil
about ½- to ¾-inches in diameter and 3 to 5 inches long. Lay the roll across
the palm of one hand (palm up), and starting at one end, squeeze the roll between
the thumb and forefinger over the edge of the hand to form a flat, unbroken
ribbon about 1/2 to 3/4 inches thick. Allow the ribbon as formed to
hang free and unsupported (Figure A3.4). Continue squeezing and handling
the roll carefully to form the maximum length of ribbon that can be supported
only by the cohesive properties of the soil. Use Table A3.7 to draw conclusions.
Figure A3.4. Ribbon Test Technique.
Table A3.7. Ribbon Test Results and Indications.
Result Indication
Sample holds together for a length Highly plastic and highly com-
of 8 to10 inches without breaking
Soil can be ribboned only with
pressive (CH)
difficulty into 3-inch to 8-inch
lengths
Low plasticity (CL)