FAQ — frequently asked questions¶

General¶

Is LiquiTer NX free?¶

LiquiTer NX is part of the GeoStru NX suite with a freemium plan:

Free: access, full calculation, CSV export
Subscription: Word report, AI Import, multi-site batch, priority support

For details: geostru.ai or info@geostru.ai.

Do I have to install anything?¶

No. LiquiTer NX is a web app that opens from nx.geostru.ai/liquiter/ in any modern browser. Works on Windows / Mac / Linux PCs.

Does my data go through GeoStru servers?¶

Calculations happen server-side (in GCP cloud, encrypted). Projects are saved to your device as .json when you press Save. We do not share data with third parties.

If you need confidential data handling (forensic reports, military sites): contact us privately for on-premise hosting options.

Input¶

Where do I find a_g and Mw for my site?¶

a_g (NTC 2018): from parametri-sismici.geostru.ai with coordinates + return period (nominal life × Cu × P_VR)
Mw: from the maximum expected magnitude of the seismogenic zone INGV (DISS database). For Italy: Calabria/Friuli ~ 7.0, Central Apennines ~ 6.5, Po Plain ~ 5.5–6.5, Sardinia < 5.5.

Ground category without Vs,30¶

NTC 2018 allows estimation from geotechnical tests:

Cat. C: dense sandy/gravelly soils, stiff clays
Cat. D: loose granular soils, soft clays
Cat. E: 5–20 m alluvial layer on a Cat. A substrate

When in doubt, assume the worst case or run MASW to measure Vs,30.

How much does the result change between Seed and Boulanger?¶

In typical clean/silty sands, the difference is within 10–20% on the FSL. Boulanger-Idriss tends to be more conservative in silty sands. Run both and compare — if both give LPI > 5 the site is critical (agreement between methods strengthens the conclusion).

Can I use LiquiTer on clays?¶

No, not directly. True liquefaction concerns saturated sands and silty sands. For clays the phenomenon of cyclic softening (cyclic degradation of undrained strength) may exist, but it requires different methods (Boulanger-Idriss 2007 for clays, Bray-Sancio 2006). LiquiTer does not currently implement cyclic softening.

Clays with > 35% of particles < 5 µm are automatically excluded from the calculation (NTC 2018).

Can I use LiquiTer on a slope?¶

LiquiTer NX assumes horizontal ground. On slopes the presence of a static shear stress (K_α correction) modifies CRR. Slope analysis would require a dedicated method — at the moment we only use K_α = 1 (horizontal), conservative for not-too-steep slopes.

Calculation¶

What does "Run calculation" do?¶

For each depth z along the stratigraphy:

Computes stresses σ_v, σ'_v
Computes CSR (Seed-Idriss)
Computes CRR with the selected method
Applies MSF and K_σ
Computes FSL = (CRR · MSF · K_σ) / CSR
Marks the layer as liquefiable if FSL < FSL_limit

Then integrates LPI and settlements.

I see FSL = 99 in some layers. Why?¶

FSL = 99 (or "non-liquefiable") means the layer:

Is above the water table (unsaturated soil)
Has % clay > 35% (excluded by NTC)
Is at depth > 20 m (excluded by NTC)
Has N-SPT too high to be liquefiable (very dense soil)

All of these are cases where the calculation is logically bypassed.

The default limit safety factor is 1.25, can I change it?¶

Yes. Default 1.25 (NTC 2018). You can set 1.0 (EC8) or 1.5 (conservative analysis). Edit it in the Limit safety factor field. The calculation itself is unchanged — only the colour-coding threshold (what is "red" vs "green") and the LPI counting change.

Exports¶

The Word report won't open¶

Check that you have Word 2016+, LibreOffice 6+, or Google Docs
Open as a fallback in LibreOffice (it always handles .docx)
If the issue persists, contact us at info@geostru.ai with the file attached

I want to customise the Word template¶

For now the template is centralised. For a custom template (firm logo, fonts), write to info@geostru.ai.

My question isn't here¶

Write to us and we'll add it.