Design foundations from footing to pile cap.

ILX Foundation is a foundation and geotechnical engineering application for Windows, built for structural engineers who need foundation design driven directly by the parameters in a geotechnical report. Rather than forcing you to translate soil borings, bearing values, and pile capacities into a generic spreadsheet, ILX Foundation lets you build a layered soil profile once and then run every foundation module — spread footings, combined footings, pile groups, sheet pile walls, braced excavations, lateral pile analysis, and slope stability — against that same site model. Files are saved with the .ilxf extension and carry the complete site, loads, and analysis state in a single portable document.

The application bridges the gap between geotechnical input and structural output. Bearing capacity is computed by the classical Terzaghi, Meyerhof, and Hansen formulations; structural design of concrete footings follows ACI 318-19; pile capacity uses the α-method in clay and the β-method in sand; lateral pile behavior uses the p-y method of Reese & Van Impe; and slope stability uses the Bishop Simplified Method. Each module produces a transparent, auditable derivation with pass/fail status against the governing limit states.

Why a site-driven model? Foundations rarely fail because the concrete was under-designed — they fail because the soil assumptions were wrong or applied inconsistently across modules. By making the soil profile the single source of truth, ILX Foundation guarantees that the footing, the pile, and the slope all see the same groundwater table, the same layer strengths, and the same surcharges.

ILX Foundation is also a full participant in the ILX Suite. Through the IPC bridge it can receive column reactions directly from ILX Structures, eliminating manual re-entry of factored loads, and it returns lateral subgrade spring stiffness (k_h) values back to the structural model so that soil-structure interaction is consistent in both directions.

Your first workflow looks like this:

1. Launch ILX Foundation and create a new project with Ctrl+N, giving it a name and project number.
2. On the Site tab, enter your soil layers from the geotechnical report — thickness, unit weight, friction angle, cohesion, and SPT N-values — and set the groundwater depth.
3. On the Foundations tab, add a module (for example a spread footing) and enter its geometry.
4. On the Loads tab, apply the column reactions, either manually or imported from ILX Structures.
5. On the Analysis tab, click Run Checks and review the results.

ILX Foundation is a native Windows desktop application. The analysis solvers — particularly the p-y lateral pile iteration and the Bishop circular surface search — benefit from a faster CPU, while the soil profile and results visualization benefit from a discrete GPU. The table below lists minimum and recommended configurations.

Component	Minimum	Recommended
Operating System	Windows 10 64-bit (21H2)	Windows 11 64-bit (23H2 or later)
CPU	Quad-core 2.5 GHz (Intel i5 / AMD Ryzen 5)	8-core 3.5 GHz (Intel i7 / AMD Ryzen 7) or better
RAM	8 GB	16 GB or more
GPU	DirectX 11 integrated graphics	Dedicated GPU with 2 GB VRAM (for slope contour rendering)
Storage	2 GB free (SSD recommended)	5 GB free on NVMe SSD
Display	1920 × 1080	2560 × 1440 or higher, 100% scaling

Note: The slope stability contour plot and the p-y deflection profiles are GPU-accelerated. On integrated graphics these will still render correctly but may redraw more slowly during interactive search. A .NET 8 runtime is installed automatically by the setup package if it is not already present.

Install ILX Foundation as follows:

1. Download ILX-Foundation-Setup-1.4.exe from your ILX Studio account portal.
2. Right-click the installer and choose Run as administrator.
3. Accept the license agreement and choose an install location (default C:\Program Files\ILX Studio\Foundation).
4. The installer registers the .ilxf file association and writes the InstallPath registry key used by the IPC bridge.
5. Launch the application and sign in with your ILX Studio credentials on first run to activate your seat.

Licensing is seat-based. Each user signs in with their ILX Studio account, and a seat is checked out to that machine. You can manage your active seats — release a seat from a retired computer, or move a seat to a new workstation — from the Account → Seats page in the application or through the my.ilxstudio.com admin portal. A single seat permits concurrent installation on a primary and a secondary machine for the same engineer, but only one active session at a time.

Updates are delivered through the in-app updater. When a new build is published, a banner appears on the Home tab; choosing Install Update downloads the differential patch, closes the application, applies it, and relaunches. Beta channel builds (such as the v1.5 seismic and lateral-pile previews) can be opted into under Settings → Updates → Channel. License entitlements are re-validated on each update.

To create a new foundation project:

1. Choose Home → New or press Ctrl+N.
2. In the New Project dialog, enter the project name, project number, client, and location.
3. Select the design method (LRFD or ASD) and the code edition (ACI 318-19 is the default). These can be changed later under Settings.
4. Choose your unit system — US Customary or SI.
5. Click Create. The project opens with an empty soil profile and no foundation modules.
6. Save immediately with Ctrl+S; the project is written as a single .ilxf file.

To open an existing project, choose Home → Open or double-click any .ilxf file in Windows Explorer — the file association created during installation launches ILX Foundation directly. Recently opened projects appear on the start screen and under Home → Recent. Because the entire site model, all foundation modules, the applied loads, and the last computed results are stored inside the .ilxf file, a project is fully portable: e-mail it to a reviewer and they see exactly what you saw, including the soil profile and the analysis output.

ILX Foundation uses a ribbon interface organized by workflow stage. The tabs progress from left to right roughly in the order you use them: define the site, add foundations, apply loads, analyze, review results, and report.

Ribbon Tab	Contents
Home	New, Open, Save, Save As, Undo / Redo, Recent projects
Site	Soil layers, groundwater table, surcharges, site notes
Foundations	Add module: spread footing, combined footing, pile group, sheet pile wall, braced excavation, lateral pile, slope
Loads	Apply column reactions (manual entry or import from ILX Structures via IPC)
Analysis	Run checks, run slope search, run p-y solver
Results	Checks table, settlement, bearing diagram, p-y curves, slope contours
Report	Generate PDF, preview, report settings
Settings	Units, design method (LRFD / ASD), code edition, display

The central viewport shows whatever object is selected. With the site selected it renders the layered soil profile to scale with the groundwater table and surcharge symbols. With a foundation module selected it shows the foundation geometry over the relevant soil layers — for example a spread footing with its plan dimensions, depth, and the soil column beneath it. You can pan the viewport by holding the middle mouse button and zoom with the scroll wheel; Ctrl+0 zooms to fit.

The properties panel docked on the right edits every parameter of the selected object. Selecting a soil layer exposes its thickness, total and effective unit weight, friction angle, cohesion, and SPT N-value. Selecting a footing exposes its plan dimensions, thickness, embedment, column size, and reinforcement. Changes in the properties panel mark the project dirty and invalidate the previous results until you re-run the analysis.

The footing module designs shallow foundations against both the soil (bearing, sliding, overturning) and the structural concrete (shear, flexure, development). Three footing types are supported.

Type	Description	Typical Use
Isolated	Single concentric or eccentric column on a rectangular pad	Interior and edge columns
Combined	Two columns on one footing with proportional load distribution to keep the resultant within the kern	Property-line columns, closely spaced columns
Strap (cantilever)	Two separate pads joined by a rigid grade beam (strap) that redistributes eccentric load	Exterior column near a boundary plus an interior column

Bearing capacity is computed by the classical methods — Terzaghi, Meyerhof, or Hansen — selectable per project, with shape, depth, and inclination factors applied per Meyerhof and Hansen as appropriate. The allowable bearing pressure q_allow is derived from the ultimate bearing capacity with the global factor of safety, and the program also reports net versus gross bearing pressure with the surcharge and overburden accounted for. Structural design follows ACI 318-19: one-way (beam) shear at distance d from the column face per §22.5, two-way (punching) shear on the critical perimeter at d/2 per §22.6, flexural reinforcement in both directions per Chapter 13, and development length per §25.4.

To add a footing:

1. On the Foundations tab, click Add Module → Spread Footing (or Combined Footing).
2. In the properties panel, enter the plan dimensions B × L, the footing thickness, and the embedment depth D_f.
3. Define the column(s): size, location, and material.
4. Set the concrete f′_c, reinforcing grade, and clear cover.
5. On the Loads tab, apply the axial load, moments, and shears for each load case.
6. On the Analysis tab, click Run Checks; results populate the checks table on the Results tab.

For combined footings the program automatically positions the footing so the centroid of the pad aligns with the resultant of the two column loads, keeping the eccentricity within the kern and the bearing pressure trapezoidal rather than triangular wherever possible.

The pile module designs deep foundations for axial capacity, computing skin friction layer-by-layer through the soil profile plus end bearing at the tip, and then assessing group behavior. Both driven piles and drilled shafts are supported.

Pile Type	Section Options	Capacity Method
Driven pile	H-pile, closed/open pipe, precast concrete	α-method (clay), β-method (sand), end bearing
Drilled shaft	Cast-in-place circular	α-method (clay), β-method (sand), end bearing

Skin friction in cohesive layers uses the α-method, where the unit shaft resistance is α times the undrained shear strength s_u, with α determined from s_u per the API/Tomlinson correlation. In cohesionless layers it uses the β-method, where the unit shaft resistance is β times the effective vertical stress, with β derived from the friction angle. End bearing is computed from the bearing capacity factor N_q (sand) or 9·s_u (clay) acting on the tip area. The allowable capacity applies separate factors of safety to shaft and tip resistance.

Group capacity is the lesser of the sum of individual pile capacities reduced by the group efficiency factor (Converse-Labarre or center-to-center spacing rule) and the block failure capacity, in which the group is treated as a single equivalent pier with perimeter shear plus base bearing. The program reports both mechanisms and governs by the smaller.

To add a pile group:

1. On the Foundations tab, click Add Module → Pile Group.
2. Choose the pile type and section, and enter the embedded length and tip elevation.
3. Lay out the group: number of rows and columns and center-to-center spacing.
4. Confirm the soil layers the pile passes through; the program slices skin friction at each layer boundary and the groundwater table.
5. Apply the cap load on the Loads tab and run the analysis.

Two earth-retention modules share the same soil profile and pressure framework. The sheet pile module designs flexible cantilever and single-anchored walls; the braced excavation module designs internally supported cuts with struts or tiebacks.

Module	Configurations	Method
Sheet pile wall	Cantilever, single-anchored	Free-earth support; Rankine / Coulomb active & passive pressures
Braced excavation	Multi-level struts or tiebacks	Apparent pressure diagrams (Peck 1969); basal heave (Terzaghi)

For sheet pile walls the program builds the active and passive pressure distributions using Rankine or Coulomb theory (selectable), accounting for the groundwater table, surcharges, and wall friction. The required embedment depth is found by the free-earth support method — satisfying moment equilibrium about the anchor (or toe, for cantilevers) — and the program reports the maximum bending moment, the required section modulus, and, for anchored walls, the anchor force. A factor is applied to the computed embedment to provide the customary margin.

For braced excavations the lateral pressure follows Peck's 1969 apparent-pressure envelopes, with the appropriate diagram selected automatically based on soil type (sand, soft-to-medium clay, or stiff-fissured clay) and the stability number. Strut or tieback loads are computed from tributary areas using the hinge method, and a basal heave check is performed by Terzaghi's bearing-capacity analogy, reporting the factor of safety against the cut bottom heaving upward.

1. Add the module from Foundations → Add Module.
2. Enter the retained height, the dredge/excavation line, and the support elevations (anchor or strut levels).
3. Confirm soil layers, groundwater, and any surcharge from the Site tab.
4. Run the analysis to obtain embedment, moments, section modulus, and support loads.

The analysis engine coordinates every module against one shared site model. When you run an analysis it first resolves the effective stress profile from the layer unit weights and the groundwater table, then dispatches each foundation module to its appropriate solver: the closed-form bearing and structural checks for footings, the layered capacity summation for piles, the equilibrium solver for retaining structures, the iterative finite-difference p-y solver for lateral piles, and the method-of-slices search for slope stability. Results from every module are collected into a single checks table with explicit pass/fail status and the governing demand-to-capacity ratio.

To solve:

1. Ensure the site, foundation geometry, and loads are complete — incomplete inputs are flagged with a yellow warning badge in the properties panel.
2. On the Analysis tab, click Run Checks for the footing, pile, and retaining modules.
3. Use Run Slope Search to launch the circular surface search and Run p-y Solver for lateral pile analysis.
4. Watch the status bar for the solve progress; when complete, the Results tab is enabled.

A built-in self-test validates the solvers against published benchmark problems — a Terzaghi strip-footing example, a Reese soft-clay p-y example, and a Bishop slope textbook case — and can be run from Settings → Diagnostics → Run Self-Test. If any benchmark deviates beyond tolerance the application reports it and recommends reinstalling, which guards against corrupted solver libraries.

Every module reports its limit states against the governing code and a target factor of safety. The spread footing checks are summarized below; analogous tables exist for piles, retaining walls, and slopes.

Limit State	Criterion	Reference
Gross / net bearing pressure	qmax ≤ qallow	Terzaghi / Meyerhof / Hansen
Eccentricity	Resultant within the kern	e ≤ B/6, L/6
Sliding	FS ≥ 1.5	Soil-base friction + passive
Overturning	FS ≥ 1.5	Resisting / driving moment
One-way (beam) shear	φVc ≥ Vu at d	ACI 318-19 §22.5
Two-way (punching) shear	φVc ≥ Vu at d/2	ACI 318-19 §22.6
Flexural reinforcement	φMn ≥ Mu, both directions	ACI 318-19 Ch.13
Development length	provided ≥ ld	ACI 318-19 §25.4

Design method note: When the project is set to LRFD, structural checks use factored loads with strength-reduction factors φ per ACI 318-19, while geotechnical stability (bearing, sliding, overturning) uses service loads with a global factor of safety. When set to ASD, allowable-stress combinations are used throughout. The active method is shown in the report header so reviewers know which combinations governed.

The lateral pile module solves the soil-pile interaction problem using the p-y method of Reese & Van Impe. The pile is modeled as a beam on a nonlinear Winkler foundation, with the soil represented by depth-dependent p-y curves — soft clay, stiff clay, and sand formulations are built in and selected automatically from each soil layer. The governing beam-column differential equation is solved by finite difference, iterating until the soil reactions and pile deflections converge.

The solver produces full profiles versus depth of deflection, bending moment, shear, and rotation, and reports the maximum of each along with the depth at which it occurs. Critically for suite interoperability, it also outputs the equivalent lateral subgrade spring stiffness k_h at each node, which can be passed back to ILX Structures so that the structural model uses soil springs consistent with the actual nonlinear soil response.

1. Add a Lateral Pile module from the Foundations tab.
2. Enter the pile section, flexural stiffness EI, and head fixity (free, fixed, or partial).
3. Apply the lateral shear and any applied head moment on the Loads tab.
4. Click Run p-y Solver on the Analysis tab.
5. Review the deflection, moment, shear, and rotation profiles on the Results tab, and export the k_h springs for ILX Structures via the IPC bridge if desired.

Because the p-y curves are nonlinear, the reported k_h is a secant stiffness consistent with the computed deflection level; re-running at a different load level updates the springs accordingly.

The slope stability module evaluates the factor of safety against circular rotational failure using the Bishop Simplified Method. The slope geometry and the soil layers come from the site model; the program discretizes a candidate failure circle into vertical slices, sums the resisting and driving moments accounting for the interslice normal forces, and iterates to the converged factor of safety for that circle. It then searches a grid of circle centers and radii to locate the critical surface — the one with the minimum factor of safety.

Results are visualized as an F_s contour plot over the search grid, with the critical circle drawn on the slope cross-section and the minimum factor of safety annotated. A pseudo-static seismic option applies a horizontal seismic coefficient k_h to each slice for seismic slope stability, reporting the seismic factor of safety alongside the static value.

The Results tab consolidates every module's output. Display modes include:

Display	Shows
Checks table	All limit states, demand/capacity ratios, pass/fail
Settlement	Immediate and consolidation settlement estimates
Bearing diagram	Pressure distribution beneath footings
p-y curves	Deflection, moment, shear, rotation versus depth
Slope contours	Fs contour grid with critical circle

ILX Foundation generates a complete, auditable PDF report for any project. The report opens with the soil profile and groundwater table, lists every input for each foundation module, shows the full derivation of bearing capacity, pile capacity, embedment, p-y profiles, or slope factor of safety as applicable, and closes with the checks table and pass/fail summary. To generate, choose Report → Generate PDF; use Preview to review on screen before exporting.

Report settings under Report → Settings control the firm name and logo, the engineer of record, the cover page, which modules are included, the level of derivation detail (summary versus full hand-calc style), and whether the soil profile and result diagrams are embedded. The output conforms to the ILXReport standard so that it can be combined with output from other ILX Suite tools into a single coordinated calculation package.

The Settings tab controls project-wide and application-wide preferences. Project-level settings (units, design method, code edition) are stored inside the .ilxf file; application-level settings (display, updates, firm defaults) persist across projects.

Setting	Location	Options
Unit system	Settings → Units	US Customary, SI
Design method	Settings → Design	LRFD, ASD
Code edition	Settings → Design	ACI 318-19 (default), earlier editions
Bearing capacity method	Settings → Design	Terzaghi, Meyerhof, Hansen
Earth pressure theory	Settings → Design	Rankine, Coulomb
Factor of safety targets	Settings → Design	Editable per limit state (default 1.5 sliding/overturning)
Display theme	Settings → Display	Light, Dark, System
Soil profile scale	Settings → Display	Auto, fixed vertical exaggeration
Update channel	Settings → Updates	Stable, Beta
Firm info & logo	Settings → Firm	Name, address, logo, engineer of record
IPC bridge	Settings → Integration	Enable / disable, port (default 7744)

Error: Bearing capacity not computed — missing soil strength. This appears when the soil layer beneath a footing lacks the parameters the chosen bearing method requires (for example a friction angle for a cohesionless layer or a cohesion value for clay). Open the Site tab, select the bearing layer, and supply the missing strength parameter, then re-run.

Error: p-y solver did not converge. The finite-difference iteration failed to reach equilibrium, usually because the applied lateral load greatly exceeds the soil resistance or the pile is too short. Verify the pile embedded length, confirm the soil p-y curve type matches the layer, and reduce the load or extend the pile. If it persists, increase the node count under Settings → Diagnostics.

Error: Slope search found no valid surface. The circular-surface search grid did not contain any kinematically admissible circle, typically because the search grid does not span the slope geometry. Widen the center grid and radius range, and confirm the slope profile entry and groundwater table are correct.

Error: IPC import failed — ILX Structures not detected. The bridge could not reach ILX Structures on its localhost port. Ensure ILX Structures is running, that the IPC bridge is enabled in both applications under Settings → Integration, and that no firewall is blocking the loopback port. You can always enter the column reactions manually as a fallback.

Application logs. If you need to send diagnostics to support, the full logs are written to %LOCALAPPDATA%\ILX Studio\Foundation\Logs\. Attach the most recent log file to your support request.

Appendix A — Conventions

Convention	Meaning
code	File paths, registry keys, and literal values
Ctrl+N	Keyboard shortcut
→	Menu / ribbon navigation path
qallow, su	Geotechnical symbols (allowable bearing, undrained shear strength)
FS	Factor of safety

Appendix B — File Management

Projects are stored as single .ilxf files containing the site model, all foundation modules, applied loads, and the last computed results. Use Save As to branch a design study. The application keeps timed autosave snapshots so that a crash recovers your most recent work; recovered files are offered on the next launch.

Appendix C — Validation

The solvers are validated against published benchmarks: Terzaghi and Meyerhof strip-footing examples, Reese & Van Impe p-y case studies, and Bishop slope textbook problems. Run Settings → Diagnostics → Run Self-Test to confirm your installation reproduces these benchmarks within tolerance. ILX Foundation is an engineering aid; the engineer of record is responsible for verifying all results.

Appendix D — Accessibility

The interface supports keyboard navigation throughout, high-contrast light and dark themes, and adjustable UI scaling. Result diagrams use colorblind-safe palettes, and the checks table can be read by screen readers.

Appendix E — Support & Logs

Contact support at support@ilxstudio.com. Logs are at %LOCALAPPDATA%\ILX Studio\Foundation\Logs\. Include your version number (Home → About) and the relevant .ilxf file when reporting an issue.

Appendix F — Glossary

Term	Definition
α-method	Skin-friction method for piles in cohesive soil, scaling undrained shear strength by α
β-method	Skin-friction method for piles in cohesionless soil, scaling effective vertical stress by β
Free-earth support	Sheet-pile method assuming the toe is free to rotate, solved by moment equilibrium
p-y curve	Nonlinear soil-reaction (p) versus pile-deflection (y) relationship used in lateral analysis
Bishop method	Method of slices for circular slope stability including interslice normal forces
Kern	Central region of a footing base within which a resultant keeps the entire base in compression
Basal heave	Upward failure of the soil at the bottom of an excavation

Appendix G — Revision History

Version	Date	Notes
1.0	2025	Initial release: spread/combined footings, pile groups, sheet pile walls, braced excavation, PDF reports
1.4	2026	Lateral pile p-y solver, IPC bridge with ILX Structures, kh spring export, expanded code checks

Appendix H — Design Checklist

• Soil layers, unit weights, and strengths entered from the geotechnical report.
• Groundwater table and surcharges set correctly.
• Design method (LRFD/ASD) and code edition confirmed.
• Column reactions applied for all governing load combinations.
• All bearing, sliding, overturning, shear, flexure, and development checks pass.
• Pile capacity governed by the correct mechanism (individual vs. block) and group efficiency applied.
• Retaining embedment, moments, and support loads within section capacity.
• Slope factor of safety meets the target for static and (if applicable) seismic cases.
• Report generated, reviewed, and sealed by the engineer of record.