In an effort to reach the middle of the slab that was surrounded by grade beams we embarked on excavating a 3 deep tunnel from the west side. From there we could access the area between the grade beams. We excavated using chipping hammers with spade bits (shovels) on the end of them. Once we reached the middle we began to excavate with compressed air. We could work safely under the center area in the tunnels because we excavated them out deep enough so that if the slab suddenly lowered that there was still enough room to still crawl safely out.
I was on site every day and under the foundation every day observing and making adjustments. I soon realized that even from the center of the slab compressed air was doing little against the rock hard clays. We were concerned that by using high pressure water that we could exacerbate the moisture heave problem in the clays. We soon realized that this approach was the only one that was having any effect…. However the concern of causing future problems under the slab from the moisture of the high pressure sprayers were minimized for the following reasons.
- We quickly followed short bursts of high pressure water to break up the very hard clays with highly compressed air that removed those wet soils.
- The high compressed air to remove the soils was also high flow (375 cubic feet per minute), was very hot and very dry and circulated air under the entire under slab area drying the entire area very quickly.
- All of the perimeter areas were open and open to circulation during off hours drying out this area.
- The areas we were excavating were from several inches up to a foot or more below the slab. Any swelling during our excavation time would give us pre swell with that large gap as a cushion. With the installation of the MoistureLevel system the soils would only get lower over time.
I understood that quickly alternating between high pressure water and highly compressed air was more effective because it not only broke up the hard clays, but any water that soaked in to the clays directly adjacent started to soften those very hard clays so that the compressed air could dislodge them. I soon got to know the optimal timing between the air and water to get the maximized effect.
For those of you who remember my post “how I got to where I am today” recounting my beginnings might remember a picture I posted of myself with my workers…. All of us dirty to the max. Well. The picture below is a replay on that.
As you can see I was rolling around under the slab for 12 and 14 hour days. I purchased heavy duty ear muffs to protect my ears from the extremely loud screaming noises of the compressed air because ear plugs were not effective enough and goggles to protect my eyes from flying, mud, sand and gravel flying all over the place. I was clear that I needed heavy duty elbow and hand protection from commando crawling and working under the sharp rocks still connected to the bottom of the slab.
As you can see I had bruises up and down and all over all sides my entire body, from working under the slab. I also had scabs on my elbows and the back of my hands from being scrapped. The good thing about the extremely loud noise was that nobody could hear me cursing and yelling at the top of my lungs while under the foundation.
After weeks and weeks of this work we began to make progress. I showed my foreman the areas that I needed to be excavated in order to lower the remaining high areas. I returned to Phoenix to attend to ownership duties that I had neglected during the intervening time. I felt good about being able to finish up with a proven plan and clear instructions to finish…… false summit.