# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DcOO4JRgjWp
- **Gondola URL:** https://gondola.cc/posts/69422663-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/bad66ea982.jpg
- **Posted:** 2026-08-19T12:54:24.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

The first filling of a new dam is the real test. Everything before it is calculation.

A dam is one of the few structures deliberately loaded to its full design condition on day one. Water pressure rises with depth at roughly 9.81 kilopascals per metre, so a 100 metre head presses close to a megapascal against the heel. That thrust does not act alone. Water also works upward through the foundation rock as uplift, trying to float the dam off its own base.

First impoundment is therefore staged, not rushed. The reservoir is raised in increments, held, and watched:

- Piezometers reading pore pressure inside the embankment and the foundation
- Measuring weirs logging seepage, where clarity matters more than volume, since cloudy water means soil is moving
- Inclinometers and survey targets tracking deflection and settlement
- Jointmeters recording movement between concrete monoliths
- Thermistors following heat of hydration deep inside mass pours

An arch dam is expected to deflect downstream by tens of millimetres and to close its vertical contraction joints as it does so. Movement is not failure. It is the design working. Stillness in the instruments is often more suspicious than motion.

The spillway trial is the loud part. Water down a steep chute reaches 30 to 40 metres per second, fast enough that a surface irregularity of a few millimetres can trigger cavitation, where local pressure drops to vapour pressure and collapsing bubbles pit concrete. Aeration ramps draw air into the flow to cushion those implosions. At the toe, a stilling basin forces a hydraulic jump that converts kinetic energy into turbulence and heat before the river is handed back.

Most dam failures occur within the first years of service, usually through seepage quietly carving a path. First filling is where that path either announces itself or stays hidden.

A dam is not finished when it is built. It is finished when the water agrees.

#stemantics #civilengineering #hydraulics #geotechnical #damengineering

## Stats

- **Views:** 28,707
- **Likes:** 476
- **Shares:** 0
- **Comments:** 9

## Tags

geotechnical, damengineering, civilengineering, stemantics, hydraulics

---
Copyright (c) Gondola