Did you wash and shake the hydrometer specimen for the sieve test? If not, and you used two separate specimens as per the ASTM STPs, then it's possible that the hydrom specimen may have had a greater percentage of P200 than the shook gradation sample and this will cause an issue.
@MTNClimber: Many firms along the front range use the Denver Swell procedure in place of the ASTM method. I do not recommend the procedure in that video as there are potential issues.
There is most definitely an error somewhere. Ensure you are using the correct specific gravity for this material and also double check the dry mass of the specimen.
If the lab is using a mechanical hammer, it shouldn't matter if several techs are involved. However, if the points are being pounded by hand by different techs, it can have an effect on the results (unless they are taking turns pounding lifts).
Sieves #8,16,30,50,100 & 200 are commonly used for highway or materials testing. For geotechnical soils testing, sieves #10,20,40,60, 100(or 140) & 200 are most common.
I believe that the older USBR classification method used the 0.005 mm as the clay demarcation. ASTM D422 is now withdrawn and ASTM D7928, the current procedure for the hydrometer test does list 0.002 mm as the clay size.
the report is graphing total pore pressure during the shear phase, not excess pore pressure. My guess is that the total chamber pressures are roughly 1, 2 and 3 ksf greater than the pore pressure at the beginning of the shearing phase. The strain rate seems reasonable. Not sure why they haven't...
Normal load = stress * area. Watch your units.
If you want to apply a normal stress of 1000 psf over an area of 0.0203 ft2 (dia = 1.93"), the load would be 20.316 lbs. Our equipment has a beam ratio of 10, so we would apply 2.0316 lbs.
I think you may be confused. D2487 is the USCS soil classification system and D7928 is the hydrometer (sedimentation) portion of a particle size analysis. D2487 does not require the results for D7928. Perhaps you are wondering about the difference between the historical version for particle size...
It is never up to the lab to decide specific parameters for geotechnical tests.
From ASTM D2435:
1.3 It shall be the responsibility of the agency requesting
this test to specify the magnitude and sequence of each load increment, including the location of a
rebound cycle, if required, and, for...
No. 200 sieves are essential to USCS soil classification therefore quite commonly used. As Ron stated, wet sieving is the optimal method to determine %passing .075 mm.
