In-Situ Density Test 3

[charnott]

The main contractor is required to demonstrate the fill placed in layers and compacted by rollers is 95 or 98% of its MDD. The in-situ test selected by the Contractor is the sand-replacement test with associated OMC/MDD from lab testing. Nuclear density gauge was ruled out due to issues associated with radioactive permitting in the country.

Now the Contractor has to achieve 95% of MDD of fill with a different grading including up to 5% 300mm dia. According to BS1377 testing procedure sand replacement and even nuclear density are no longer valid tests since the maximum particle size is too great. An alternative test has been recommended by the project designer, the Water Replacement test (WRT) (ASTM D5030-04). Given the maximum particle size it seems the test-ring and excavation will need to be approx. 2m in diameter and as such is a rather laborious and inefficient test method.

Furthermore the designer has confirmed that the frequency of testing should be the same when using the WRT as when using sand-replacement testing which is completely impractical given the work involved with undertaking each WRT.

I am interested to know if anyone can point me in the direction of an in-situ denity test applicable for material with a maximum particle size 300mm other than SRT, Nuclear Denisty or WRT?Some advice Ive been given points me to a plate-load test (standard not specified) however Im struggling to see how I can derive a %compaction in order to meet the requirements of the specification.

Rather long-winded but hope its clear enough to those who know the field. Any help much appreciated.

 

[fattdad]

12-in diameter maximum partical size is extreme! I mean you'd have to consider 2-ft lift thickness and lord knows what compaction equipment would be in use.

I'd have to consider how uniform the materials are and to what extent the quality control should be performed using a test pad.

Just to point out, the obligation of the contractor is to return to the project the fill as specified (i.e., gradation, classification, density). The promise is the compaction, not the compaction test method. If the contractor has control over the borrow and 12-in diameter is allowed by the specifications, then what method is the contractor using to control the quality?

f-d

¡papá gordo ain’t no madre flaca!

 

[Ron]

I would not allow fill with 300mm size particles. There is no reasonable, accurate or efficient way of testing compaction in such materials for quality assurance.

 

[BigH]

So rockfill for dams is out of the question? We use the water replacement method and, yes, it is labourious in that we have rock sizes up to 800 mm (least dimension) - but we do only for 1 in 10k m3. I think that you should consider a test trial whereby the "settlement" is measured after each pass or two until you get no more "compaction settlement." Then you will know how many passes are required. Of course, a lot depends on the use of the fill - what is its purpose and what is it supporting or is it an embankment, etc.

 

[charnott]

fatdad - The 2m diameter test ring has come from the contractors review of the ASTM water replacement test procedure. The COntractor is required to verify that the fill has been compacted to obtain a density of at least 95% of modified Proctor MDD. MDD to be obtained using BS1377 test method or similar approved standard (here lies the opportunity to spec a more appropriate test) The grading is required to be 100% passing 300mm, 95-100% passing 125mm and 0-10% passing 600micron.

Ron - herein lies the problem, the designer has provided the required grading and required the contractor to verify the %compaction. we have a second garding of fill on the project with max particle size 75mm, i believe that the requirement for %MDD compaction was intended for that fill and a generic statement that the >300mm fill must also be compacted to 95% was a poorly thought out afterthought. Nevertheless the Contractor didnt query this during tender or during the first 2 years of the contract, only now that he is starting the works and we're stuck with the spec as it is!

BigH - The issue is the scale of the job, this area of the project will take more than 10Mm3 so the numbers of tests involved are huge! We've already undertaken tens of thousands of SRT on the millions of m3 we've already placed but the comparative cost and time implications of WRT vs SRT will have signiifcant implications for the successful delivery of the project. The fill is purely to raise site levels for future development, the location is the area surrounding a new port project so end -use will likley be a industrial support type business however its currently unknown. Howevere common sense thinking like that isnt welcomed by the client who wants his pound of flesh 'im paying for 95% MDD, i want 95%'!

 

[GeoPaveTraffic]

Previous advice has been very good, particularly that by BigH. Limitied tests by the water test method are often peformed for rock fill dams with most of the fill just observed.

For this project, the simple solution would appear to be to limit the partical size to smaller material so that nucular or sand replacement tests can be used.

Mike Lambert

 

[Panars]

I would recommend you determine the compaction effort it takes to attain the 95% requirement as tested by the WRT method, and then have the contractor use that same compaction effort on the rest of the fill. If the material stays the same, the compaction equipment stays the same, and the number of passes remains the same, you should get the same results. This will allow you to reduce the number of Water Replacement tests required. You will basically use the WRT to convert the performance specification into a method specification.

 

[charnott]

GeoPaveTraffic - unfortunately the gradings are as per the contract/specification and have been decided by the designer based upon the anticipated grading of our excavated material, all our reclamation fill is site won from our port basin and transported to reclamation areas to raise site levels. The problem lies in that the designer has specified a grading where up to 5% may be 125-300mm but has not provided an appropriate test methodology to validate compaction of that material, now they're scrambling and specifying a test which is wholly inappropriate given the volumes involved.

Panars - this seems a sensible approach given that we know the grading of the material will be consistent through our regular PSD/uniformity testing. We have asked the contractor to undertake a compaction trial at the moment and I will put this forward to designer and contractor in my review of that trial results.

Thanks to one and all for your input, highly appreciated.

Regards

Chris

 

[Panars]

Glad to help, and I hope it works out for you.
FYI, if you find a post helpful, you should click on the purple star that says "Thank ____ and star this post!"

 

[Ron]

BigH...you are right as usual! I was thinking smaller fills, of course. Rather than a specific density requirement that can't be easily verified, I would look toward a proof-rolling technique or using a control strip method to determine subsequent acceptance.

 

[charnott]

The Contractor has now submitted a relationship between plate load derived modulus ration and degree of compaction in his latest attempt to avoid ASTM water replacement testing. However the supporintg technical documents are in French and German (the contractor is CHinese!). Until such time as I can get them to provide an English explanation of the relationship does anyone here have any experience with such a relationship??

The bare bones of it seem to be:
EV2/EV1 <2.3 equals 100% Dpr (degree of compaction)
EV2/EV1 <2.5 eqauls >98%
EV2/EV1 <2.6 equals >97%

Any thoughts??