In my previous blog, I began some observations of life lessons I learned while working at a geotechnical lab while in college. This blog will complete the lessons, at least the ones I think I learned and can remember.
When the previously described field samples arrive at the lab, the testing begins. It is important to know the type of soil with which you are dealing. One way to figure out the soil type is to determine the Atterberg Limits. This evaluation essentially requires two tests.
One test involves putting a soil sample in a little bowl, using a tool to make a proscribed groove in the sample, and then turning a crank to tap the bowl onto a surface and count the tippy-taps required to close the groove. This, as you can imagine, is a VERY important number! So, you may ask what we do with the sample after we tippy-tap the groove closed? Very simply, we throw it against the lab wall and see if it sticks! This is a non-ASTM test, but one that is both entertaining and moderately useful.
Lesson: Sometimes you have to throw a bunch of ideas against the wall and see which ones stick.
The other test requires rolling a soil sample into a ‘worm’ across an etched glass surface. You all probably did something similar with play dough when you were six (Yes, this is very close to rocket science!). You keep rolling it until the ‘worm’ breaks, or in other words, it no longer maintains its ability to adhere to itself. Then you check its moisture content. What do you do when you are finished with the soil ‘worms’? You put them into a big coffee can, of course.
Lesson: Some people see a can of worms, while others see something useful and of value.
Another interesting lab test involves breaking concrete test cylinders. This is necessary to ensure that samples of concrete taken from construction sites have achieved the strength necessary to comply with the intended design. The interesting thing about this test is that often the testing machine applies more and more force to the test cylinder for longer and longer time…and nothing appears to be happening. Tension builds as the dial nears the assumed breaking strength. Then, without warning…BOOM! Immediate, dramatic and loud failure occurs and you hope you don’t have to change into clean underwear.
Lesson: Sometimes it takes a lot of time, patience and pressure before you realize a desired outcome.
And finally, another lesson from the construction site. Geotechnical firms are often called upon to verify that soil is properly compacted during site grading projects. This requires the technician to flatten a spot on the surface and then use various methods to determine if the particular soil has achieved the required density. If not, typically a contractor is not happy with the message you are giving them.
As the ‘college kid’, I was assigned to inspect a grading project during the overnight shift of a 24/7 grading project. Large grading equipment was crawling all over a subdivision site during the middle of the night. When it was time for a test, a large scraper would come by and blade me a flat spot. I would park my trusty little Datsun lab truck next to the spot and do the test. After only one or two tests, the grading contractor foreman came up to me and suggested that if I would take the test right in front of my pickup’s headlights, and not off to the side in the near-darkness….he could probably better ensure that his equipment operators would not turn me into a grease spot in the dirt because they could not see me.
Lesson: It’s always good if someone is watching your back!