### id262791393 engineers flatten building sites for long-term stability > The natural landscape is never ideally suited to construction as it stands. The earth is just too uneven. Before things get built, we almost always have to raise or lower areas of the ground first. We flatten building sites, we smooth paths for roads and railways, and we build ramps up to bridges and grade-separated interchanges. You might notice that these cuts and fills usually connect to the existing ground on a slope. Loose soil won’t stand on its own vertically. That’s just the nature of granular materials. The stability of a slope can vary significantly depending on the type of soil and the loading it needs to withstand. You can get many types of earth to hold a vertical slope temporarily, and it’s done all the time during construction, but over time the internal stresses will cause them to slump and settle into a more stable configuration. For long-term stability, engineers rarely trust anything steeper than 25 degrees. That means any time you want to raise or lower the earth, you need a slope that is twice as wide as it is tall, which can be a problem. - [View Highlight](https://read.readwise.io/read/01fqy75nk7b2yq7vzhsd6s5m0q) - [[Why Retaining Walls Collapse by Grady Hillhouse#id262791393 engineers flatten building sites for long-term stability|View in Vault]] - [n] This will be useful for [[Civil Mage]] and [[Irella]] and potentially some prequel stuff with her that I need to collect because I know I've said this before #xref