Lab

Class,

I don’t think it is practical for us to obtain actual topsoil samples for our Loam Grain Size Lab due to the weather. I have unpublished this assignment, but I do not want to change the Overview. You can see the example I produced to make the instructions. A great exercise to do when teaching soil classification.

All you need to do for the other lab exercise is to use Play-Doh to demonstrate the physical test for cohesiveness, or a role test. We perform a visual and a physical test for all three elements for soil classification. We can look at grain size as a visual test for cohesiveness and then perform a role test where we make a 1/8-inch-thick string of the soil. If we can it confirms cohesiveness.

Next we perform a visual test for fissuring. Again, we have a visual test inspecting for cracking, flaking, etc and then pat out a 1 inch thick by 2-inch-wide disk and allow it to dry naturally. If it stays together and does not crumble easily, it is not fissured material. Usually fissuring material will crack or come apart as it dries and easily crushes.

Since we dont have real soil that is all. But in the real world we use a thumb test and confirm with a pocket penetrometer, and some use pocket shear vane testers to determine TSF.

We do these to practice our classification skills but to also see how I was taught and how I teach soil classification to safety students and operators. It is a good idea to have several real samples available for learners to describe, and perform visual and physical tests on. In order to be qualified a learner should be able to perform a thumb test and be accurate with the penetrometer test at least 80% of the time.

Remember, qualified persons have DEMONSTRATED KNOWLEDGE AND SKILL. SKILL BEING EXEMPLIFIED WITH EXPERIENCE. QUALIFIED PERSONS MUST HAVE TWO SKILLS DEMONSTRATED, CONTROL OF ACTIVITY AND ABILITY TO RECOGNIZE AND AVOID HAZARDOUS CONDITIONS. Documenting the class learning and the practicals go along way to proving qualified status. You can then eval and document the same practical elements in the field to document successful experience.