Compaction Testing Science

What's your fill plasticity ratio?

I tried posting a response to this thread, but the dang CR4 site ate it twice! Flew off into cyberspace!.

First obtain a free downloadable file UFC 3-220-10N "Soil Mechanics" from the USACE Publications website here:

http://www.wbdg.org/ccb/browse_cat.php?o=29&c=4

Then Google search Troxler Density Test, Standard Proctor Density Test, and Modified Density test, to learn the differences between them.

While you're at the USACE site, find an applicable Technical Specification dealing with pavement subgrade & subbase construction and the necessary compaction testing procedures. A lot depends on the type of pavement: flexible (asphalt) vs. rigid (PCC).

Good afternoon guys,

The location is the Central Highlands, carved into the upper bank of a large valley of a small creek. The building has been built. The owners have always had funding problems, which has caused this project to drag on over several years. They are just now getting ready to install the UG hookups to the street, then the subgrade preparation. The automobile parking lot is ~ 100' x 350', including the bldg.

I was asked to prepare to witness the soil tests, not as an official soil mechanics expert, rather as an observer of general location, #, type, date, weather, etc., prior to them being sent to a lab. I wanted to have some basic general knowledge of the testing, so I wouldn't appear too ignorant.

I downloaded & scanned the recommended document. Based on zero training and experience, I'd guess the soils range from Residential Sands (Generally favorable for foundations) to Residential Clays (Variable Properties).

I notice the Extreme Frost Penetration is ~7.5" in this area.

I have since been told the City will assume this task. Thx all for your responses.

What part of AZ are you in? You need to first know your soil types before worry about the rest.

bakerjohn is correct. You need to the soil types in your locale. You can get these from your county, like the Cornell Cooperative Extension (if available there). More importantly, you can contact the local office of the USDA Natural Resources Conservation Service (NRCS), formerly the Soil Conservation Service. They'll have soil maps and pertinent data for all soil types in your area. Also, your county Planning Dept. may have the soil maps on their GIS database, if they are so equipped.

http://www.nrcs.usda.gov/wps/portal/nrcs/main/national/home

As far as the different soil density testing methods and their respective capabilities, you could obtain the appropriate ASTM specifications for each online, but they are not free for the updated versions. You may be able to find pirated versions to download via a Google Search. Frankly, if you had no formal soil mechanics course or field experience they will be of little use to you.

You could find an online a free ebook download of the latest edition of "Foundation Design" authored by Prof. Joesph E. Bowles, P.E.. He has a chapter that discusses the various soil density testing methods. If you find an older edition it may not include the Troxler test.

Sure you can do the soil compaction methods that you mentioned. And sheepsfoot rolling is a consideration, especially for initial compaction of deep fill areas. Frankly, I would limit the individual lifts of an engineered soil to 12-inch maximum loose lifts, and test each lift per specification (method, quantity, and location). Actually, I prefer vibratory rolling for consolidation of each placed lift whenever possible, but you must get the soil moisture close as possible to the optimum moisture content.

A lot of engineers specify 90% minimum Modified Proctor Density under pavements. I've always liked using at least 95%, because of the future consolidation issues, especially with asphalt pavements placed over deep fill areas. If you have a very good excavation Contractor, who is diligent, your compaction densities may approach 100%.

I think your best bet is going to the USACE Publications website that I provided you and downloading everything you can regarding soil mechanics, soil compaction testing methods and procedures, subgrade and subbase construction, and pavement construction. Hey, they are free for the taking; you already paid for them w/ your Federal Income Taxes etc. It would be an understatement to say they are comprehensive. Besides, you will learn a lot about soil mechanics from them if you're a layman.

Unfortunately, there's not enough time in the day (or the space herein) to discuss and teach you the specifics regarding the various testing methods and advice that you asked for. Sorry about that!

Let us know how you made out, okay?

USDA has several web base soil survey programs which a great I do a custom report through them all the time. AZ unlike many of the local governments in the North East don't have county resources for soil surveys its much easier to go online I agree with all your other statements it much easier and cheaper to get a local soils inspector in then try this on your own for the first time without the training. Like I said before depends on location and soils types. You'll never get away will 12" lifts with DG degraded granite which is very common here or fine sands in the west valley but you could get it from clay sources only the Rim. Consulting an expert in that field is you best bet to get the best product.

If it is a large enough paving project, it is essential to hire a local Geotechnical Engineer to oversee soil borings and laboratory soils testing + furnish an Engineering Report which outlines construction means and methods, and field testing.

Cheap insurance for very expensive pavements, to assure that it is done correctly. I can't stress that one singular requirement enough. Most people ignore that and later pay dearly for premature pavement failures and shorten pavement lifespans.....

Airfield, as in aircraft, parking?

You are so right. I got caught up in one some years back where the engineer had no F%#$ clue as to what he was doing. Million pounds of jolt to be applied from this molding machine, not including the total weight of the unit. Setting on a mixture of peat and layers of clay. Company I worked for at the time did listen and hired proper engineer to come up with solution to footings. Been running almost 30 years and has not driven its self to the bottom of the pit yet.

Moral of story, do it right do it once.

fixit, I'm glad that the company that you once worked for had the good sense to hire a geotech engineer and do it right from the onset! Also, glad to hear that the foundation design has been working out after 30 years. In-situ Peat and clay soils are extremely difficult to design for.

What happened to the original engineer who didn't have a clue? Fired?

All too often over the years I have run into designs completed by moonlighting engineers who are state or county or town employees. Most are young engineers who have just passed the PE exam and are looking for a quick buck to supplement their incomes. Most have only worked for Gov't., which carries it's own mindset vs. those engineers that have worked in the private sector. Often they do not carry Professional Engineer's insurance of any type. Many of these guys are only in it for a fast buck, and what is worse, they don't have the necessary experience to complete the designs in a proper manner. Many are done so haphazzard that it is downright scary, They aren't doing their clients any great big favors, that's for sure!

Capt. The firm who sold the bag of goods was replaced. The Engineer (head) from the company I worked for also went by by. Big mess, but could have been allot worst. The Plant Manager is the person I presented my findings to. He made the call on the rest. Found an engineer out U of Chicago who knew what he was doing.

Funny thing I didn't even get a pat on the back for that one. Might be why I quit! Oh well!