First, the answer to Vol. 11 (last week).
When I arrived on-site, I first thought maybe the site was hit with an overnight rain shower! Conditions looked like the photo below. A couple sips of coffee later and I realized the road wasn’t wet, so I got out to investigate.
Scott and David both nailed it! Hydrostatic pressure! We did a proof-roll of the subgrade for an access road/clay berm extension on the right side of the first photograph and it failed. No sign of water. A bridging lift was placed which cracked and again, no sign of water. This process probably took a week or so, and simultaneously, the contractor was excavating off the topsoil to expose borrow materials for a cell being constructed to the north of this area (trees are south). Eventually, with the topsoil overburden removed (there were also large piles of old trees on the area that were removed first) and traffic disruption, the uplift suddenly occurred all at once! It was perched water that existed in a sandy silt, sandy clay mix above a much more impermeable clay (our borrow material). Ironically, when we dug the test pits for material sampling 2-months prior, no water was encountered!
In these blog posts, Do You See What Glen Sees, I will present a photograph or short video related to earthwork or geosynthetics construction and have you identify the significance of what you’re seeing.
It could be things being done correctly or incorrectly. Primarily, these will be things that impact quality.
In addition to my blog, I’ll post this content on X and LinkedIn. You can post your response on one of those two.
I’ll give you my thoughts on each photo or video when I post the next installment.
Do you see what I see? Or did you find something I missed? I’m excited to find out!
