California Bearing Ratio Test - Soil Properties: Testing, Measurement, and Evaluation - page 405

[B] Unit Weight Determination

The area and volume of the specimen are easily computed as follows:

2

p D 2
4

p 1 6.00 2

Area

28 . 27 in . 2

4

Volume height area 5.00 28.27

141.35 in. 3

1 21 2

The mass of the compacted soil specimen can be determined by sub-
tracting the mass of the mold from the mass of the mold plus compacted
soil specimen:

Mass of specimen mass of mold specimen mass of mold

1 2 1 2

Mass of specimen before soaking 9,020.90 4,167.50 4,853.40 g
Mass of specimen after soaking 9,036.81 4,167.50 4,869.31 g

Wet unit weights g wet can now be determined:

a 4,853.40
141.35

ba 1,728
453.6

g wet before soaking 130.8 lb

ft 3

b >

a 4,869.31
141.35

ba 1,728
453.6

g wet after soaking 131.2 lb

ft 3

b >

(The numbers 1,728 and 453.6 are conversion factors: 1,728 in. 3

1 ft 3 ;
453.6 g 1 lb.) With the water contents having been computed
previously, dry unit weights

γ dry can be determined next:

130.8
18.3 100

g dry before soaking 100 110.6 lb

ft 3

a b >

131.2
19.5 100

g dry after soaking 100 109.8 lb

ft 3

a b >

[C] Swell Data

The swell percentage is computed by dividing the final (swell) dial
reading by the initial height of the specimen:

dial reading
initial height of specimen 100

final 1 swell 2

0.0135
5.00 100 0.27 %

Swell

[D] Bearing Ratio

Respective piston loads can be determined by multiplying each proving
ring dial reading by the proving ring calibration. Then each penetration
stress can be obtained by dividing the piston load by the area of the pis-
ton (which is 3 in. 2 ). Hence, for the penetration of 0.025 in., the piston
load is 0.0004 74,000, or 29.6 lb, and the penetration stress is

29.6/ 3.00, or 9.9 psi.

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