> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/templates/box-culvert-workflow/loading-bc/lateral-earth-pressure-bc.md).

# Lateral Earth Pressure \[BC]

Lateral Earth Pressure applies the horizontal soil pressure on the culvert's exterior walls using the equivalent-fluid method: the pressure grows linearly with depth as if the retained soil were a fluid of a given unit weight.

Two cases are generated, a maximum and a minimum, because the governing combination differs by effect. High lateral pressure controls the wall's own bending; low lateral pressure removes the arching restraint on the frame and can control the slabs. Both are produced so the limit-state combinations can take whichever governs.

The wall loads are sliced along the barrel rather than applied as one full-length polygon, which is what makes them work on a curved alignment.

## General

**Box Culvert:** The culvert barrel this pressure is applied to. A selection is required. The load is applied to the barrel's exterior wall surfaces.

**Stage:** The construction stage this load is activated in. Leave it empty for a model that is not staged.

**Soil Side \[Left/Right/Both]:** Which exterior wall or walls carry the pressure. Use Both for a culvert with fill on both sides; a single side models a wall that is exposed.

**Max Equivalent Fluid Unit Weight (EHmax):** The equivalent fluid unit weight for the maximum lateral pressure case. MnDOT LRFD 12.2.3 quotes 0.060 kcf for at-rest conditions. Must be positive.

**Min Equivalent Fluid Unit Weight (EHmin):** The equivalent fluid unit weight for the minimum case, quoted as 0.030 kcf by the same reference. Must be positive and not greater than the maximum.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.openbrim.org/templates/box-culvert-workflow/loading-bc/lateral-earth-pressure-bc.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.