Which tool, when?

The SlipSurface IQ family deliberately contains tools that answer the same question two ways: a slope can be solved by limit equilibrium (LE) or by finite elements (2D); a sheet pile wall by limit equilibrium or by beam-spring. The table below maps typical engineering questions to the right tool.

By question

Your question	Tool	Why
What is this slope's factor of safety, and where is the critical slip surface?	SlipSurface IQ LE	Eight methods and thousands of surfaces in seconds; the standard route for reports and comparisons.
What if the slip surface isn't circular, or there is soil-structure interaction?	SlipSurface IQ 2D	Under strength reduction the mechanism falls out of the deviatoric strain field.
How far does the wall move during excavation, and what happens to the anchor loads?	SlipSurface IQ 2D or SlipSurface IQ SPWA	2D solves the continuum; SPWA is faster and makes the sheet pile design checks.
Is the sheet pile's embedment and section enough?	SlipSurface IQ SPWA	Free-earth support + staged Winkler, stress and deflection checks, a section database.
Which failure do the joints in this rock slope allow?	SlipSurface IQ Kinematic	Markland test, stereonet, Monte Carlo probability.
How many bolts, how long, for the critical rock wedge?	SlipSurface IQ Kinematic	Wedge/planar/toppling limit equilibrium and a bolt spacing × length matrix.
What c′, φ′ and modulus does this rock mass have — around a tunnel, under a slope?	SlipSurface IQ Rock	Generalised Hoek–Brown, GSI five ways, every application and modulus estimate side by side.
Can this footing carry this load, and how wide must it be?	SlipSurface IQ Bearing	Six factor sets side by side, EN 1997-1 design approaches, the width required.
How much, and how fast, will the raft / fill settle?	SlipSurface IQ Settle	Immediate + consolidation + secondary, t50/t90, angular distortion.
How long must the pile be, what does the group carry, how much does it settle?	SlipSurface IQ Pile	α/β/λ, four group efficiencies, block failure, required length, equivalent raft; compression and uplift under seismic loads.
How long must the rock socket be?	SlipSurface IQ Pile	Twelve published correlations and a design length.
Is the reinforcement of this MSE wall enough?	SlipSurface IQ MSEW	FHWA/AASHTO external and internal stability, ASD or LRFD, the required length.
Is this cantilever wall stable, and which bars does it need?	SlipSurface IQ Wall	Four earth pressure methods, TBDY 2018 earthquake, TS 500 design, reinforcement drawing and DXF.

Shared code between siblings

The family shares code, too:

• MSEW's and Wall's bearing capacity factors are SlipSurface IQ Bearing's. The bearing capacity of the wall's base is computed with the same factors.py and capacity.py.
• Kinematic's two modules plot on one stereonet. Screening and limit equilibrium use the same projection, and the most critical component found in screening goes to limit equilibrium in one click.
• LE and 2D check each other. 2D's 2:1 slope test is made against an independently written Bishop search (1.377 against 1.381).

By analysis type

	2D	LE	Kinematic	Rock	Bearing	Settle	Pile	SPWA	MSEW	Wall
Limit equilibrium		●	●		●		●	●	●	●
Finite elements / springs	●							●
Deformation / settlement	●					●	●	●
Staged construction	●							●
Earthquake (pseudo-static)		●	●		●		●	●	●	●
Groundwater	●	●	●		●	●	●	●	●	●
Reliability / probability			●	●	●	●	●	●
PDF / HTML report	HTML	JSON/CSV/SVG	PDF	●	●	●	●	●	●	●
Turkish interface			●	●	●	●	●	●	●	●
DXF import	●

A calculation program does not replace engineering judgement

Read the limitations on each program's Reference page. SlipSurface IQ 2D, for example, has no consolidation and no hardening soil model; SlipSurface IQ MSEW does not check global and compound stability — use SlipSurface IQ LE for that.