Humboldt H-4340 Sand Equivalent Test Set with Case - Manual (Page 9)

• Continue to apply a stabbing and twisting action while flushing the fines upward
until the cylinder is filled to the 15 in. (381 mm) graduation. Then raise the irrigator
tube slowly without shutting off the flow so that the liquid level is maintained at
about the 15 in. graduation while the irrigator tube is being withdrawn. Regulate
the flow just before the irrigator tube is entirely withdrawn and adjust the final level
to the 15 in. graduation.
9. Allow the cylinder and contents to stand undisturbed for 20 min ± 15 seconds. Start
the timing immediately after withdrawing the irrigator tube.
10. At the end of the 20 min sedimentation period, read and record the level of the
top of the clay suspension as prescribed in 12 below. This is referred to as the “clay
reading”.
If no clear line of demarcation has formed at the end of the specified 20 minute
sedimentation period, allow the sample to stand undisturbed until a clay reading
can be obtained; then immediately read and record the level of the top of the clay
suspension and the total sedimentation time. If the total sedimentation time exceeds
30 minute rerun the test using three individual specimens of the same material.
Record the clay column height for the sample requiring the shortest sedimentation
period as the clay reading.
11. Sand Reading Determination:
• After the clay reading has been taken, place the weighted foot assembly over
the cylinder and gently lower the assembly until it comes to rest on the sand. Do
not allow the indicator to hit the mouth of the cylinder as the assembly is being
lowered.
• As the weighted foot comes to rest on the sand, tip the assembly toward the
graduations on the cylinder until the indicator touches the inside of the cylinder.
Subtract 10 in. (254 mm) from the level indicated by the extreme top edge of the
indicator and record this value as the “sand reading”.
NOTE 9: lf the sand reading indicator and foot is used, modify the sand reading
determination procedure given above as follows: While the weighted foot is being
lowered, keep one of the centering screws in contact with the cylinder wall near the
gradua tions so that it can be seen at all times. When the weighted foot has come to
rest on the sand, read and record the level of the slot of the centering screw as the value
for the “sand reading”.
•
When taking the sand reading, use care not to press down on the weighted foot
assembly since this could give an erroneous reading.
12. If clay or sand readings fall between 0.l in. (2.5 mm) graduations, record the level
of the higher graduation as the reading. For example, a clay level at 7.95 would be
recorded as 8.0. A sand level at 3.22 would be recorded as 3.3.
Calculation and Report
1. Calculate the sand equivalent to the nearest 0.1 % as follows:
SE=(sand reading/clay reading) X 100
where:
SE = sand equivalent.