Lythos LE

Slopes and rock

Limit equilibrium slope stability

Method-of-slices stability of slopes and embankments: eight methods from Fellenius to Morgenstern-Price, critical surface search, water, seismic, reinforcement and tension cracks — with zero dependencies.

$ pip install lythosle

Run

lythosle

Default port

8000

Python

3.9+

Version

0.1.0

Licence

AGPL-3.0

See the examples →ReferenceSource ↗

Limit equilibrium slope stability in pure Python, with a browser front end. Lythos LE computes the factor of safety of slopes and embankments with the method of slices — the same class of analysis as Rocscience Slide or GeoStudio SLOPE/W. It searches for the critical slip surface, reports every classical method on it, and draws the section in the browser.

• No dependencies. The solver, the web server and the front end are standard library and vanilla JavaScript. python -m lythosle serve works on a bare Python 3.9+ install with nothing to pip install.
• Eight methods, from Fellenius to Morgenstern-Price, all built on one slice formulation — the differences between them are the assumptions, not the code.
• Validated against closed-form solutions, Taylor's stability numbers and the ACADS benchmark problem.

What it does

Methods	Ordinary (Fellenius), Bishop simplified, Janbu simplified and corrected, Corps of Engineers #1, Lowe-Karafiath, Spencer, Morgenstern-Price (half-sine, constant or trapezoidal interslice function)
Surfaces	Circular (grid-and-tangent search with adaptive box and refinement), a single specified circle, a user-defined non-circular surface, and non-circular optimisation from the critical circle
Strength	Effective stress (c′, φ′), undrained (su, optionally increasing linearly with depth), impenetrable and no-strength materials
Groundwater	Piezometric water table, per-material pore pressure ratio ru, separate saturated unit weights, ponded water on the slope
Loading	Surface surcharges, pseudo-static kh and kv, reinforcement (nails, anchors, geosynthetics), tension cracks with optional water pressure
Output	Factor of safety per method, the critical surface, a full slice force table (CSV), the λ–FS plot for Spencer/Morgenstern-Price, the search grid, JSON for everything

Screenshots

Browser interface — light theme

Browser interface — dark theme

Quick start

pip install lythosle

lythosle serve --open         # browser interface on http://127.0.0.1:8000
lythosle example              # list the built-in examples
lythosle example homogeneous  # run one and print the report

Or straight from a clone, with nothing installed at all:

git clone https://github.com/hdaltuntas/lythosle
cd lythosle
python main.py                         # same interface
python main.py example homogeneous     # same commands
python -m unittest discover -s tests   # run the test suite

HOST and PORT override the address. If you prefer FastAPI, uvicorn lythosle.web.app:app serves exactly the same API.

The browser interface

Build the geometry from a template or by typing coordinates, set up materials, groundwater and loading in the sidebar, then Run analysis (or Ctrl/Cmd + Enter). The section view shows the layers, the phreatic surface, the critical surface with its centre of rotation, the search grid coloured by factor of safety, the slices and the reinforcement. Results export as SVG, CSV and JSON. ?example=layered_water and ?theme=dark work as URL parameters.

The fonts (Inter and Newsreader) are bundled; nothing is fetched from a CDN at runtime, and the page looks the same offline.

Next steps

• Examples — the six built-in examples, the command line, the Python API and a staged fill.
• Reference — model format, formulation, validation and limitations.