Complete workflow¶

Detailed sequence of a real analysis, from input data to the report.

Overall scheme¶

INPUT                       CALCULATION                OUTPUT
─────                       ───────────                ──────
1. Project data             5. CSR (seismic)            7. FSL(z) table
2. Site GPS · water table   6. CRR (resistance) →       8. FSL vs z plot
3. Seismic parameters           ↓                       9. LPI
4. Stratigraphy                                        10. Settlements
                                                       11. Word report
                                                       12. CSV

1. Project data¶

Fill in at least the description of the project (e.g. "Residential building — Versilia, lot B"). Site, operator and date are optional but useful for the report.

Site GPS¶

Latitude and longitude of the site are strongly recommended: LiquiTer uses them to:

Geolocate the site on the map in the report
Determine the value of a_g from the Italian seismic zonation (if the pre-fill from Parametri Sismici is enabled)

2. Water table¶

Water table depth (m) from ground level. Above the water table there is no liquefaction; below it the soils are saturated and susceptible.

Uncertain water table

If the water table depth is uncertain or varies seasonally, use the worst case (water table as high as possible). Liquefaction is a safety check: better conservative than optimistic.

3. Seismic parameters¶

Code¶

Mandatory selection. LiquiTer supports:

NTC 2018 (Italian D.M. 17/01/2018) — reference for the Italian territory
Eurocode 8 (EN 1998-5) — European, equivalent on many points

Ground category (A · B · C · D · E)¶

Determined by Vs,30 (average shear-wave velocity in the top 30 m). If you don't have a measured Vs, use the geotechnical stratigraphy:

Cat.	Description	Vs,30
A	Rock	> 800 m/s
B	Soft rocks or very dense coarse-grained soils	360-800
C	Dense coarse-grained soils or stiff clays	180-360
D	Loose coarse-grained soils or soft clays	< 180
E	Shallow alluvial layers on a substrate	(special case)

Topographic category (T1 · T2 · T3 · T4)¶

Affects the topographic amplification factor S_T:

T1 — flat ground or slope < 15°
T2 — slope 15-30°
T3 — isolated ridge 15-30°
T4 — isolated ridge > 30°

a_g (peak ground acceleration)¶

Peak ground acceleration, in g (e.g. 0.15 g). From the INGV grid for the site coordinates + return period (nominal life × Cu × P_VR).

Magnitude Mw¶

Moment magnitude of the design earthquake. Used by the magnitude scaling factor (MSF) in most methods (Seed, Tokimatsu, Boulanger-Idriss). Typical range for Italy: 5.5–7.0.

4. Stratigraphy¶

Stratigraphy tab — define the layers one by one:

Field	Meaning
Top/bottom depth	top and bottom elevations of the layer (m)
Lithology	sand / silty sand / clay / gravel / etc.
γ (unit weight)	kN/m³ — total above the water table; saturated below
N-SPT	blows/30 cm from SPT (Standard Penetration Test)
qc	tip resistance from CPT (MPa) — if available
Vs	shear-wave velocity (m/s) — if available
% clay	clay fines fraction (relevant for liquefiability)

Which test to use

SPT is the most common in Italy → use Seed or Tokimatsu
CPT is more precise and continuous → use Boulanger-Idriss
Cross-hole / down-hole (Vs) → use Andrus-Stokoe

If you have several tests, run the calculation with different methods and compare.

5. Calculation¶

Results tab → press Run calculation.

For each depth, LiquiTer:

Computes σ_v (total vertical stress) and σ'_v (effective)
Computes the depth reduction coefficient r_d as a function of depth
Computes CSR = 0.65 · (a_max/g) · (σ_v/σ'_v) · r_d (Seed-Idriss 1971)
Computes CRR with the selected method (see methods)
Computes FSL = (CRR / CSR) · MSF · K_σ (with scaling factors)
Determines whether the point is liquefiable (FSL < FSL_limit, default 1.25)
Computes LPI integrating the contributions of the liquefiable layers
Estimates post-seismic settlements (Ishihara-Yoshimine 1992 method)

6. Inspect the results¶

Table by depth¶

One row per calculation step:

z	σ_v	σ'_v	r_d	CSR	CRR	FSL	Verdict

The verdict is colour-coded: 🟢 stable · 🔴 liquefiable.

FSL vs z plot¶

Vertical FSL profile. The red vertical line is FSL = 1 (liquefaction threshold). Points to the left are critical.

LPI index (Iwasaki)¶

LPI	Risk
0	Negligible
0–5	Low
5–15	Medium
> 15	High

7. Export¶

Export in the toolbar:

Word report (.docx) — technical report with figures, KPIs and tables
CSV — raw data for further analysis

Details →

Summary diagram¶

flowchart TD
    A[Project data] --> B[Water table]
    B --> C[Seismic parameters]
    C --> D[Stratigraphy]
    D --> E{Method}
    E -->|SPT| F[Seed / Tokimatsu]
    E -->|CPT| G[Boulanger-Idriss]
    E -->|Vs| H[Andrus-Stokoe]
    F & G & H --> I[Run calculation]
    I --> J[FSL by depth + LPI + settlements]
    J --> K[Export Word/CSV]

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