Earthworks quality control

[Rendang71]

Dear All,

Recently, I was assigned to supervise the earthworks at several sites for housing projects. One of the cases is like this, the contractor brought the material for filling purpose. We call this Class 3 Material, according to our spec the material should have the gradation as follows : passing 100 mm sieve (100%); passing 5 mm sieve (0-50%) and passing 0.075 mm sieve (0-20%). Lab compaction test was performed, we came to know that this material has portion passing 37.5 mm sieve and 20 mm sieve were 65% and 51% respectively (silty, sandy GRAVEL, according to BS 5930-1999). In BS 1377-1990 Part 4, it says when the gradation of material falls into Grading Zone X, where the portion passing 37.5 mm and 20 mm sieves are less than 90% and 70%, then the lab compaction is no longer applicaple because the material is too coarse to be tested. But, the laboratory managed to do this lab compaction test, and obtained OMC of 16% and max dry density of 1.8 Mg/m3, which I believed that they just performed the compaction test on the material passing 20 mm sieve.

My questions are :
1. Is there any other way to test this sample and also the field compaction quality control method? Because when the lab test is no longer applicable, then we won't have any reference to control the soil density on site.
2. Can I use plate load test to check the field compaction quality?


Thanks in advance,

Rendang71

 

[fattdad]

ASTM D698 addresses oversize correction. While you may not have ASTM specified for your project you can learn the methods for oversize correction and these methods may have been used by the testing firm.

Don't know.

f-d

¡papá gordo ain’t no madre flaca!

 

[Rendang71]

Thank you fattdad for your comments. FYI, based on the sieve analyses itself, the gradation of the material falls into Grading Zone X where the material will not be possible to be tested under this Lab Compaction method. In BS 1377-1990 Part 4 there is correction of oversize material, when the material falls into Grading Zone 5, where the portion of material passing 37.5 mm and 20 mm sieves are 90% and 70%. Under this condition, the amount of material retained on 37.5 mm sieve will be replaced with the same amount of material passing 37.5 mm sieve and retained on 20 mm sieve.

Regards,

Rendang71

 

[BigH]

Sadly - this is where specifications should be very very specific - identify what you wish and what kind of compaction testing you wish to use. Unless you have a "lab" test result, you will not be able, under your spec, to determine the % relative compaction in the field. For "oversized" gradations - there was another recent thread on it - look for it.