SlipSurfaceIQ LE

2D limit equilibrium slope stability analysis with a desktop CAD interface — version 2026.4.0

2026.4.0 release notes — Python scripting tutorial (PDF), main icons in a vertical column on the left, only the ACADS examples bundled, an empty scripting editor, English-only interface, signed update manifests and a safer delta updater.

SlipSurfaceIQ LE is an open-source program for checking the stability of soil and rock slopes, cuts and embankments with the limit equilibrium method (LEM). You draw the slope cross-section, assign materials, add groundwater, loads and supports, and the program searches for the critical slip surface and its factor of safety (FS) with the classic methods of slices — Bishop, Janbu, Spencer, Morgenstern-Price/GLE and others.

The workflow follows the layout geotechnical engineers know from commercial tools such as Slide2: a Modeler window for building the model and a separate Interpret window for the results, which shows a slip-centre FS contour map, the critical surface, slice data and a professional PDF report.

The interface and reports are in English. The program runs on Windows, Linux and macOS.

Engineering disclaimer. SlipSurfaceIQ LE is provided without any warranty. Results depend entirely on the input geometry, strength parameters, groundwater and loads. Always review and verify them with engineering judgement and, where it matters, with independent calculations or software.

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Contents

• Highlights
• Installation and start-up
• A typical workflow
• The Modeler window
• The Interpret window
• Calculation engine
• Material models
• Groundwater, seismic loads and tension cracks
• External loads
• Supports and facings
• Critical surface search
• PDF report
• Project files, DXF and Python scripting
• Bundled examples
• Verification
• Keyboard and mouse reference
• Development
• Project layout
• Roadmap
• License

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Highlights

• Nine limit equilibrium methods — Bishop simplified, Ordinary/Fellenius, Janbu simplified and corrected, Corps of Engineers #1 and #2, Lowe-Karafiath, Spencer and GLE/Morgenstern-Price (four interslice functions).
• Circular, non-circular and user-defined slip surfaces with an automatic global search (differential evolution + Nelder-Mead), slope limits and a minimum depth.
• Eleven strength models — Mohr-Coulomb, generalized Hoek-Brown, Hoek-Brown (mb, s, a), Undrained (Tresca), SHANSEP, Hardening Soil, SANISAND, power-law envelope, Power Curve, Barton-Bandis, CNI rock mass.
• Groundwater by water table (with per-material Hu) or Ru coefficient, ponded water, pseudo-static seismic loading and tension cracks with crack water.
• Supports — end-anchored anchors, grouted tiebacks, soil nails, geotextiles, geosynthetics and micro-piles, single or as automatically placed bolt patterns; shotcrete + wire-mesh facing.
• CAD-style drawing with rulers, adaptive grid, SNAP / GRID / ORTHO / OSNAP, typed coordinates (x,y, @dx,dy, @length<angle) and unlimited undo/redo.
• Results: slip-centre FS contour map with a banded legend, critical surface, lowest 25 surfaces, FS legend for all methods, slice query, text report and notes/shapes on the drawing.
• Detailed computing dialog showing method, search stage, generation, surfaces evaluated / valid / rejected, best FS, elapsed and remaining time and a log.
• Professional PDF report with cover, contents, summary, tables, figures and appendices.
• DXF import/export of the geometry and a built-in Python scripting console.
• Light / dark theme, windows sized to the detected screen.

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Installation and start-up

Source-only execution

SlipSurfaceIQ LE is distributed as Python source code. There are no MSI, DEB, RPM, Arch or PyInstaller application packages, no installers, and no separate launcher scripts. The only supported application entry point is main.py. Python 3.10 or newer and the dependencies from requirements.txt are required.

Get the repository using Git or download its source archive and extract it. Run these commands from the repository root:

python -m pip install -r requirements.txt
python main.py

For an isolated environment (recommended):

python -m venv .venv
# Windows PowerShell: .venv\Scripts\python.exe -m pip install -r requirements.txt
# Windows PowerShell: .venv\Scripts\python.exe main.py
# Linux / macOS: .venv/bin/python -m pip install -r requirements.txt
# Linux / macOS: .venv/bin/python main.py

You can also run main.py directly from VS Code, PyCharm, or another Python IDE, using an interpreter with the dependencies installed. Neither pip install -e . nor OS-level package installation is required.

On minimal Linux desktops, install the Qt runtime shared libraries from your operating system's repository if PySide6 reports that they are missing:

sudo apt install libegl1 libgl1 libxkbcommon0 libfontconfig1 libdbus-1-3       # Debian / Ubuntu
sudo dnf install libglvnd-egl libglvnd-opengl libxkbcommon fontconfig dbus-libs  # Fedora
sudo pacman -S libglvnd libxkbcommon fontconfig dbus                            # Arch Linux
sudo zypper install libglvnd libxkbcommon0 fontconfig libdbus-1-3              # openSUSE

Command line

python main.py                                    # empty project, window sized to the screen
python main.py examples/acads_1a.slp.json         # open a project file
python main.py --example "ACADS EX1(a)"           # open a bundled example
python main.py --list-examples                    # list the bundled examples
python main.py --check                            # check Python and the required packages

Update notifications

The update checker (Help → Check for Updates…, or once a day at start-up) queries the latest published GitHub release. When a newer release is found, you can click Update Changed Files to download and replace only the modified source files in place (with automatic backups in .update-backup), or open the release page on GitHub. Every file is downloaded and hash-checked before anything is replaced, so a failed or cancelled update leaves the installation unchanged; the test suite (tests/) is not part of updates, and files you keep in examples/ or docs/ are never deleted. When a release changes requirements.txt, the completion dialog offers Install Requirements, which runs python -m pip install -r requirements.txt with the same Python that runs the application. Always start the application with python main.py. Automatic checks can be disabled under Help → Check for Updates at Start-up.

Signed manifests (maintainers). Releases can sign manifest.json with an Ed25519 key (pure Python, no extra package). Run python -m slipsurface.patch.signing genkey once, store the private key only as the repository secret MANIFEST_SIGNING_KEY, and add the printed public key to TRUSTED_PUBLIC_KEYS in slipsurface/patch/signing.py. From then on the release workflow publishes manifest.json.sig, and the updater installs only from a manifest whose signature verifies. With no public key configured, updates rely on HTTPS and the per-file hashes.

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A typical workflow

The workflow bar at the top of the Modeler follows the steps of a slope model; each step shows its own toolbar.

1. Geometry — draw the external boundary (closed polygon) by clicking or typing coordinates, then material boundaries, the water table and, if needed, a tension crack line. Regions are created automatically from the boundaries.
2. Properties — define materials (Properties → Define Material Properties) and click inside the regions to assign them. Define shotcrete facing types and assign them to the slope face.
3. Loading — add distributed and line loads; set seismic coefficients in Project Settings → Seismic.
4. Support — define support types and draw single supports, click on the slope face to place bolts at a fixed inclination, or create bolt patterns.
5. Surfaces — choose circular, non-circular or a drawn user surface, the search effort and optional slope limits (entry/exit ranges).
6. Compute (F5) — the computing dialog shows the progress; when finished, the results open in the Interpret window.
7. Interpret — review the critical surfaces of all methods, query slices, add notes and create the PDF report (Ctrl+P).

Every edit can be undone (Ctrl+Z / Ctrl+Y). Changing the model invalidates the results and asks for a new computation; display-only changes (colours, labels, notes) do not.

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The Modeler window

• Menus: File, Edit, View, Analysis, Boundaries, Loading, Support, Surfaces, Properties, Tools, Help.
• Workflow bar: Geometry › Support › Loading › Properties › Surfaces, with the toolbar of the current step below it.
• Icon column (left): new / open / save, undo / redo, project settings, summary, materials, compute, interpret, PDF report, zoom and pan, select, measure, export and the note tools, read from top to bottom.
• View menu: theme, zoom, grid settings, material labels, and Display Options (colours, line width, grid, ruler, material fill, legend, slope limits). Hovering a region with the Select tool shows the material name and strength parameters; the context menu offers Edit This Material.
• Interpret left dock: Document Viewer (materials, boundaries, supports, facings, loads, notes, methods — click an item to select it in the drawing) and the same Display Options used while reviewing results.
• Dialogs: Project Settings (General, Methods, Groundwater, Seismic, Advanced), Project Summary, Define Material Properties, Surface Options, Define Support Properties, Define Facing Types, coordinate table, grid settings, display options.
• Material labels on the regions: none, name, or name + strength parameters and unit weights.
• Notes: text, line, arrow, rectangle and ellipse annotations, also on the results.
• View → Dark mode switches the theme (remembered).
• On first start the Modeler and Interpret windows open at the size of the detected screen; dialogs scale with the screen resolution. F11 toggles full screen.

CAD drawing area

• Rulers, adaptive grid, crosshair cursor, material and FS legends.
• Wheel = zoom at the cursor, middle button = pan, middle double-click / F2 = zoom all, zoom window and pan tools.
• SNAP (F9, to the grid), GRID (F7), ORTHO (F8), OSNAP (F3: endpoint, midpoint, intersection, nearest).
• Coordinate box in the status bar: x,y · @dx,dy · @length<angle · c close · u undo point · empty Enter finish.
• Editing: drag vertices, add/delete vertices, double-click for the coordinate table or the properties of loads, supports, facings and notes, Delete, right-click context menu.

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The Interpret window

• Method selector (e.g. "Spencer FS: 0.984") and Global Minimum button.
• Slip-centre FS contour map (circular searches): every admissible circle evaluated by the search contributes its centre; each grid cell shows the lowest FS of the circles centred there, smoothed into continuous bands with contour lines and a banded FS legend (0 … ≈6.4·FSmin). The critical centre carries an FS = … label, with dashed lines to the exit and entry points and the critical surface as a dashed line.
• Optional: slices and sliding-mass fill, the lowest 25 surfaces coloured by FS, spline control points — all switchable in Display Options.
• FS legend (bottom right) with the factor of safety of every method; the current method is highlighted and the global minimum shown in green.
• Slice Data query (click a slice), Information Viewer (complete text report — save or copy), image export.
• Notes and shapes on the results with their own undo/redo; they are picked by shape (on a line or arrow, inside a rectangle or ellipse), show grips and a selection frame, can be moved by dragging, edited by double-click and deleted from the context menu. They are saved in the project file and appear in the report.

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Calculation engine

Method	Equilibrium	Surfaces
Bishop simplified	moment	circular
Ordinary / Fellenius	moment (circle) / force	circular and non-circular
Janbu simplified / corrected (f0)	force	circular and non-circular
Corps of Engineers #1, #2	force	circular and non-circular
Lowe-Karafiath	force	circular and non-circular
Spencer	force + moment	circular and non-circular
GLE / Morgenstern-Price (half-sine, constant, clipped sine, trapezoidal)	force + moment	circular and non-circular

• Slicing: a chosen number of equal-width slices plus extra boundaries at every ground, water table, load and polyline-surface vertex, so the top of each slice is straight, and where the slip surface crosses a material boundary, so each slice base lies in one material. These geometric boundaries take precedence when they nearly coincide with an equal-width one, so the result does not depend on the failure direction. Slice weights are integrated through all material regions (γ above, γsat below the water table).
• Non-linear strength: for curved envelopes the solvers iterate on the effective normal stress on each slice base and use the instantaneous (tangent) c and φ.
• Admissibility: solutions with mα < 0.2 (Whitman & Bailey) or a negative mobilised base shear (tension at the base) are rejected; interslice forces above a configurable multiple of the total weight are treated as singular. Both checks can be tuned in Project Settings → Advanced.
• Failure direction: right-to-left or left-to-right (Project Settings → General).
• Geometry: the ground must be a continuous, single-valued profile y(x). Vertical slope faces and overhangs are rejected with an explanatory message; vertical sides at the outer model limits remain supported.

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Material models

Choose the model in Define Material Properties → Strength. Every material has a unit weight, an optional saturated unit weight, a colour and water parameters (whether the water table acts on it and the piezometric factor Hu).

Model	Strength	Notes
Mohr-Coulomb	τ = c′ + σ′n tan φ′
Undrained (Tresca)	τ = su	total stress, pore pressure not used
SHANSEP	τ = su = A + S · σ′v · OCR^m	A is additive; σ′v = max(W/b − u, 0) is the reference effective vertical overburden stress; total-stress analysis. Details and limitations.
Hardening Soil	τ = c′ + σ′n tan φ′	Mohr-Coulomb failure surface of the HS model; E50,ref, Eoed,ref, Eur,ref, m, pref, Rf and ψ are stored for reference — LEM uses only the failure envelope
SANISAND	τ = σ′n tan φ(ψ), sin φ = 3Mb / (6 + Mb), Mb = M exp(−nb ψ)	state parameter ψ = e − ec, critical state line ec = ec0 − λc (p′/pat)^ξ (Dafalias & Manzari 2004); in LEM p′ ≈ σ′n
Power-law envelope	τ = a · pa · (1 + σ′n/pa)^b	concave envelope for granular materials
Power Curve	τ = a (σ′n + d)^b + c	as in Slide2
Barton-Bandis	τ = σ′n tan(φr + JRCn log10(JCSn / σ′n))	joints; scale correction JRCn = JRC0 (Ln/L0)^(−0.02 JRC0), JCSn = JCS0 (Ln/L0)^(−0.03 JRC0); total friction angle ≤ 70°
CNI rock mass	τ = a · σc · ((σn − T0) / σc)^n	Cylwik, Killian & Cicchini (2023), in the variables of Slide2; instantaneous φ ≤ 70°
Generalized Hoek-Brown	σ1 = σ3 + σci (mb σ3/σci + s)^a	mb, s, a from GSI, mi and D (Hoek et al. 2002)
Hoek-Brown (mb, s, a)	same envelope	mb, s and a entered directly

The Hoek-Brown envelopes are converted to τ–σn curves (Balmer) and used with instantaneous c and φ.

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Groundwater, seismic loads and tension cracks

• Water table: u = Hu · γw · (water table − base elevation); Hu and whether the water acts are set per material. Ponded water above the ground is added to the slice weight as a vertical load only; the horizontal component of the water pressure on a sloping submerged ground surface is not modelled. Where that thrust matters (a submerged toe, a reservoir drawdown), model it explicitly with a surface-normal distributed load.
• Ru coefficient: u = Ru · σv (total vertical stress at the base).
• Pseudo-static seismic loading: horizontal force kh·W in the failure direction at the slice centroid; kv positive upward gives a vertical load (1 − kv)·W.
• Tension crack: a crack line is drawn (or created from a depth, with the Rankine z_c = 2c / (γ√Ka) as a suggestion). A slip surface crossing the line on the crest side is cut there and a vertical crack face rises to the ground. The crack can be dry, full or partially filled; the water thrust V = ½ γw hw² acts in the failure direction at hw/3.

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External loads

• Distributed loads on the ground surface between two points, uniform or linearly varying, acting vertically or normal to the surface.
• Line loads at a surface point with any direction angle.

All loads are included as forces and moments in every method.

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Supports and facings

Support type	Force T (per support, then divided by the out-of-plane spacing)
End anchored	tensile capacity
Grouted tieback	min(tensile, bond strength × min(bond length, L_out))
Geotextile	min(tensile strength, pullout × min(L_in, L_out))
Geosynthetic	min(C · tensile, P_in, P_out), P = 2 · C · ∫(adhesion + σv tan δ) ds, σv = γ · depth; anchorage none / slope face / embedded end / both ends
Micro-pile	pile shear strength

L_in and L_out are the support lengths inside and outside the sliding mass, C the strip coverage. Each support type has:

• Application: active (the force reduces the driving force) or passive (the force is mobilised like shear strength, T/F).
• Direction: parallel to the support, tangent to the slip surface, or perpendicular to the support (micro-piles).

Single bolts are placed by clicking on the slope face with a given inclination (default 15° below horizontal) and length. Bolt patterns fill a stretch of the slope face with equally spaced bolts and are edited as one object; each bolt acts as a separate support.

Shotcrete + wire-mesh facing: thickness, unit weight, shear strength τ, mesh (Q106 … Q589 or a custom As) and fy. Its weight γ·t is applied as a surface load; where the slip surface exits or enters through the faced surface, T = τ·t + As·fy acts tangent to the slip surface against sliding (passive by default).

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Critical surface search

• Circular: each candidate is defined by its two ground intersections and the central angle, so every candidate is a valid circle.
• Non-circular, polyline (default, as in Slide2): straight segments through interior vertices. After the global search all vertices of the best surface are optimised freely, then a vertex is inserted in the middle of every segment and the surface is optimised again.
• Non-circular, B-spline: smooth surface; optionally convex only.
• User-defined: a surface drawn by hand is analysed directly.
• Optimiser: differential evolution (global) + Nelder-Mead (local); non-circular searches are seeded with the critical circle of a quick circular pre-search. Search effort: fast / normal / fine.
• Slope limits: left and right ranges for the exit and entry points, drawn on the ground; optional minimum sliding-mass depth.
• The computing dialog reports the method (i/n), the current stage, generation, surfaces evaluated / valid / rejected, lowest and last FS, slices, elapsed and estimated remaining time, with a time-stamped log. The computation runs in the background and can be cancelled at any time.

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PDF report

File → PDF Report (Ctrl+P) in either window creates a report with:

• cover with project data and a critical FS card assessed against a target FS (Adequate / Marginal / Inadequate);
• contents, summary, model figure and geometry description;
• material tables, analysis and search settings, loads, supports and facings;
• results table and FS comparison chart, critical surface figures for the global minimum and for each method;
• mobilised support forces, tension crack results;
• appendices with slice data and coordinates;
• page headers and footers, "Page n / N", PDF bookmarks.

The sections can be switched on or off; author, checker and company are remembered.

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Project files, DXF and Python scripting

Project files

Projects are saved as .slp.json (format version 3). Files from earlier versions (1 and 2) are converted automatically when opened. A project stores the geometry, materials, groundwater, loads, supports, facings, search settings, display options and the notes of both windows.

DXF

File → Import DXF / Export DXF exchanges the 2D geometry. Importing replaces the current model and can be undone with Ctrl+Z.

Layer	Content
SS_EXTERNAL	one closed external boundary (alternatively a single closed polyline on layer 0)
SS_MATERIAL	material boundaries
SS_WATER	one water table polyline
SS_CRACK	one tension crack polyline
SS_SURFACE	one user slip surface
SS_SUPPORT	support lines (export only)

LINE, LWPOLYLINE, POLYLINE, ARC and SPLINE are read; curves are converted to straight segments with a 1 cm tolerance. Drawing units are converted to metres (unitless drawings are taken as metres with a warning); geometry outside z = 0 is rejected and skipped entities are listed. DXF carries geometry only — use .slp.json for materials, loads, supports and results.

The DXF Import Guide (PDF; also under Help) explains the layers, supported entities and units, a CAD preparation checklist, what happens after an import, exporting, using DXF from Python and every import message with its fix. Start a drawing from docs/DXF_Layer_Template.dxf, which has every layer. Maintainers rebuild both with python scripts/build_dxf_guide.py.

Python scripting

Tools → Python scripting opens an empty editor where a script can modify the project object (external, material_boundaries, assignments, water_table, tension_crack, materials, support_types, supports, support_patterns, facing_types, facings, loads, seismic, methods, surfaces, annotations, …). MaterialSpec, SupportType, FacingType, Project and empty_project are available. The script runs on a copy of the project; if validation succeeds, all changes become a single undoable step, otherwise the open project is left unchanged. Scripts run with your local Python permissions — run trusted code only. Scripts never run when a project is opened; a script opened from a .py file asks for confirmation before its first run.

The Python Scripting Tutorial (PDF; also under Help and the editor's Tutorial (PDF) button) explains every command: all project fields, every material model and its parameters, loads, supports, facings, settings, notes and display options, with tested examples and a complete model. Maintainers rebuild it with python scripts/build_scripting_tutorial.py; every example in it is run during the build.

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Bundled examples

The bundled examples are the ACADS verification problems. They are available under File → Examples and from the command line with --example "<name>" (python main.py --list-examples prints the names). The same models are in the examples folder as project files. File → New starts an empty project with one default material (Soil 1, Mohr-Coulomb).

Example (--example)	File	Shows
ACADS EX1(a)	acads_1a.slp.json	ACADS verification problem (homogeneous slope)
ACADS EX1(b)	acads_1b.slp.json	ACADS verification problem (three layers, weak lens; layer starts at the toe)
ACADS EX1(c)	acads_1c.slp.json	homogeneous slope with a water-filled tension crack (Craig depth 2.685 m); Spencer ref 1.592
ACADS EX1(d)	acads_1d.slp.json	the EX1(b) three-layer slope with kh = 0.15; Spencer ref 0.991
ACADS 2(a) — Talbingo critical upstream search	acads_2a.slp.json	upstream-face critical-circle search; infinite-slope reference FoS ~1.951
ACADS 2(b) — Talbingo fixed circle	acads_2b.slp.json	four-material dry embankment; exact circle (100.3, 291, 278.8); Bishop/Spencer/GLE/Janbu
ACADS 3(a) — weak seam + water table	acads_3a.slp.json	two materials, 0.5 m weak seam, water table at its base; non-circular Spencer/GLE search
ACADS 3(b) — weak seam specified path	acads_3b.slp.json	exact four-point noncircular path for a fixed-surface solver control; no critical search
ACADS EX4	acads_4.slp.json	weak seam, inclined piezometric surface and two surcharges; Spencer ref 0.761 (block search)
ACADS EX5	acads_5.slp.json	excavated 1:2 slope, water-table approximation of the published flow net; Spencer ~1.486 vs 1.500

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Verification

The ACADS Janbu validation separates Janbu Simplified from Janbu Corrected, lists method-matched Slide2 factors, and verifies published fixed surfaces. Deep-surface Janbu correction is bounded at its empirical peak; use Spencer/GLE to corroborate unusual non-circular mechanisms.

A reproducible 29-slice GeoStudio / Seequent hand-calculation reference now checks the Ordinary and Simplified Bishop equilibrium equations and the existing LE solver independently. In 2026.1.4, Ordinary's pore-pressure projection for circular moment equilibrium was aligned with the published u L cos² α formulation (non-circular force equilibrium retains u L), and the Bishop pore-water normal-force decomposition was added as a checked solver relation. See GeoStudio Hand Calculations Verification.

Additional official SLOPE/W Tutorial and Limit Equilibrium Formulation examples are now covered by exact published tutorial geometry/material/pore inputs and solver-level analytical/method tests. Vendor critical-search FS numbers are labelled reference-only until the original solved circle/search settings are available; no false cross-program equality is claimed. See Additional GeoStudio Verification.

Run python -m pytest tests/test_geostudio_handcalcs.py tests/test_geostudio_slope_examples.py -q.

Reference discrepancies: The verification discrepancy audit separates Talbingo 2(a) versus 2(b) and provides a read-only diagnostic for ACADS 3(a) and Borges–Cardoso Case 2. Do not accept very low optimized FoS without checking the actual surface and support mobilization.

The ACADS 2(b) Talbingo Dam verification adds an exact fixed-circle solver case, without an optimizer search, to check four methods on the same published surface. The circle is editable under Surface Options → User-defined → Fixed circle.

The Borges–Cardoso Case 2 geosynthetic benchmark adds a 5-layer reinforced embankment model and a new elevation-dependent undrained total-stress material (UDG). Published FoS are verification references, not hardcoded results; global critical-circle matching remains pending independent analysis.

The Arai & Tagyo VP15 layered-slope verification note provides the circular and non-circular models, material region checks, and published vendor FoS values. The benchmark global-search match remains unverified until separately calculated and reviewed.

The ACADS 3(a) verification note gives the exact groundwater/weak-seam geometry and published Spencer/GLE references. The regression tests check material regions, pore pressures, and a fixed non-circular diagnostic path; no match of optimized FS is claimed until a full critical search has been checked.

The test suite checks the engine against reference solutions, among them:

• ACADS EX1(a): Bishop 0.985, Spencer 0.984, GLE 0.984 (Slide2: 0.987 / 0.986 / 0.986).
• Planar block: every force-equilibrium method reproduces the closed-form rigid-block solution to 10⁻⁶, with seismic loads, external loads and active and passive anchors (a quadratic in F).
• Hoek & Bray planar sliding with a vertical tension crack (dry, half full, full): seven methods to 10⁻⁶.
• Bishop–GLE moment consistency with loads, passive anchors and crack water; support capacity formulas; mirror symmetry; an independent Bishop reference; the infinite slope limit; weight = area × γ.
• Tangent consistency of every non-linear strength model, the Barton-Bandis and CNI formulas, SHANSEP with the effective vertical stress, and the effect of micro-piles and geosynthetics on the FS.

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Keyboard and mouse reference

Key / action	Function
F5 / F6	compute / open Interpret
F2, middle double-click	zoom all
Wheel / middle drag	zoom at cursor / pan
F3 / F7 / F8 / F9	OSNAP / GRID / ORTHO / SNAP
F10	Information Viewer (Interpret)
F11	full screen on / off
Ctrl+Z / Ctrl+Y	undo / redo
Ctrl+P	PDF report
Enter, c, Backspace, Esc	finish, close, undo last point, cancel (drawing)
Double-click	coordinate table or properties of the picked object
Delete	delete the selection

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Development

python -m pip install -r requirements-dev.txt
python -m pytest -p no:cacheprovider --durations=15    # Qt tests run headless
python -m pytest -p no:cacheprovider -m "not slow"     # quick run without long analyses
python -m ruff check .
python -m mypy                                         # computation core

The full suite takes a few minutes because of the non-circular searches and the PDF and GUI tests (tests marked slow hold the long benchmark analyses). GitHub Actions runs the lint (including the 100-character line limit) and type checks, and the python main.py checks with the full suite on Python 3.12 and the quick suite on Python 3.10.

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Project layout

main.py              start-up script (IDE / command line)
pyproject.toml       lint, type-check and test configuration only
requirements*.txt    runtime and development requirements
slipsurface/
  geometry/          slope geometry, slip surfaces (circle, polyline, B-spline), regions from boundaries
  materials/         strength models and the model catalogue
  lem/               slicing, Bishop / Fellenius, Spencer, GLE, Janbu, Corps, Lowe-Karafiath
  optimizer/         critical surface search (differential evolution + Nelder-Mead)
  loads.py           external loads, support forces, facings, bolt placement
  project.py         project model and JSON file format
  analysis.py        multi-method runner and text report
  exchange.py        DXF import / export
  scripting.py       Python scripting
  patch/             delta self-updater and manifest signatures
  report/            PDF report (ReportLab) and fonts (Source Sans 3, SIL OFL)
  ui/                Modeler, Interpret, CAD canvas and tools, dialogs
examples/            ACADS example projects
tests/               test suite

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Roadmap

SlipSurfaceIQ LE remains an independent application, not a SlipSurfaceIQ Suite module. Its native CAD modeler, Interpret results, numerical engine, project files, licenses, source releases and version numbers stay under this repository. See the standalone development plan for the staged reliability, CAD, solver-verification and release-quality work.

Longer-term research features:

• Probabilistic analysis (Monte Carlo)
• Sarma method
• Back analysis

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License

Copyright © 2026 Hasan Deniz Altuntaş.

SlipSurfaceIQ LE is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. If you modify the program and make it available to users over a network (for example as a server or web service), the AGPL requires you to offer them the corresponding source code.

The program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose.

Third-party components and their licenses are listed under Help → About: Qt / PySide6 (LGPL-3.0), NumPy, SciPy and Shapely (BSD), ReportLab (BSD), ezdxf and QtAwesome (MIT), Material Design Icons (Apache-2.0), Source Sans 3 (SIL Open Font License 1.1).