Everything Geotechnical.
Your comprehensive geotechnical engineering analysis platform.
Select a module from the sidebar to get started!
Analyze soil liquefaction potential
Deep excavation analysis
Foundation design analysis
Select unit system for calculations and Excel report display.
Multiple levels separated by commas
| No | Soil Type | Drainage | Depth (m) | γt (kN/m³) | Illustrate | |
|---|---|---|---|---|---|---|
| Analysis above | Sand Surge Analysis | |||||
Click "Load DIGGS map" to show map
Enter water levels for each excavation stage. Use the initial groundwater level if not specified.
| Excavation Stage | Depth (m) |
|---|
Standard: USACE EM 1110-2-2504 (or FHWA GEC 4)
Rationale: Both standards use the same logic for calculating "passive earth pressure resistance against kick-out" (Free Earth Support Method).
Program Setting: Fixed FS ≥ 1.5
Standard: NAVFAC DM 7.02
Rationale: This is the most classic reference for handling heave in soft clay. When American engineers discuss Heave, they refer to NAVFAC.
Program Setting: Fixed FS ≥ 1.5
Standard: USACE / FHWA General Standards
Program Setting: Fixed FS ≥ 1.5
| No | Z (m) | A (m) | B (m) | Q (kPa) | Action |
|---|
| Layer Parameters | Layered Water Level Input Mode | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| No | Layer Code | Drainage | Depth (m) | γt (kN/m³) | c' (kPa) | φ' (deg.) | Su/σv' | SPT-N | Dw,exc (GL-m) | Dw,ret (GL-m) | Seepage Mode |
Click "Load DIGGS map" to show map
| No | Soil Type | Layer Type | Depth (m) | γt (kN/m³) | c' (kPa) | φ' (deg.) | Su (kPa) | SPT-N |
|---|
| Dw,exc (GL-m) | Dw,ret (GL-m) | Seepage Mode |
|---|
Select unit system for inputs and results.
| Type | Vx | Vy | Pz | Mx | My |
|---|---|---|---|---|---|
| D | |||||
| L | |||||
| W | |||||
| E |
| ztop (m) | zbot (m) | γt (kN/m³) | Soil Class | Drainage | Su (kPa) | c′ (kPa) | φ′ (°) | |
|---|---|---|---|---|---|---|---|---|
Click "Load DIGGS map" to show map
Pile Foundation module coming soon...
Retaining Wall module coming soon...
Image loading failed
Please place the image at: static/images/calculation_points.png
Use comma-separated groundwater levels for each impermeable interface (U layer), for example:
2, 4.5, 8.
Order must be from top to bottom interface. If fewer values are provided than interfaces, the last value is reused.
Units follow the selected unit system: m in Metric, ft in Imperial.
The groundwater levels on both the retaining side and excavation side exhibit static water pressure distribution, without considering the effects caused by water pressure differences on both sides of the retaining wall.
When using non-watertight retaining walls (steel rail piles, steel sections, soldier piles), this mode is generally applicable when the original formation exhibits static water pressure distribution. Since (after dewatering on the excavation side) the water levels on both sides of the retaining wall are the same, please enter the same value for the retaining side groundwater level Dw,ret and the excavation side groundwater level Dw,exc.
The groundwater levels on the retaining side and excavation side are different, causing seepage due to the water pressure difference at the bottom of the retaining wall. This mode is applicable to watertight retaining walls (diaphragm walls, sheet piles) in thick permeable formations (sand, gravel, cobble), without clay interlayers.
After horizontal seepage at the wall bottom, CATii automatically calculates the water pressure using the following formula:
This mode is applicable to various formation conditions. For formations with alternating sand and clay layers, it is recommended to prioritize this mode. After inputting the water levels of each layer and seepage mode according to the construction dewatering conditions, CATii can automatically calculate vertical seepage and horizontal seepage at the wall bottom. For input methods, please refer to the Layered Water Level Input Mode description.
Service loads represent the unfactored working load combinations used to evaluate foundation performance under normal operating conditions. These combinations include permanent loads (D), live loads (L), wind loads (W), and seismic loads (E), combined according to service-level requirements.
The resulting forces and moments are used to assess eccentricity effects, contact area reduction, and allowable bearing capacity under working stress conditions.
This platform evaluates seepage-induced instability using classical hydraulic gradient and uplift stability concepts widely adopted in U.S. levee and dam engineering practice.
The formulations implemented here are based on:
These methods are commonly used for preliminary assessment of uplift, heave, and piping risk in earth structures.
This equation compares the total vertical soil weight above the potential uplift plane with the upward hydraulic force generated by excess pore water pressure.
If \( FS_u < 1.0 \), uplift failure may occur. Design guidelines typically require \( FS_u \ge 1.2 \).
References: Terzaghi (1943); USACE EM 1110-2-1901
This expression is derived from the ratio \( FS = i_{cr} / i_{exit} \), where \( i_{cr} = \gamma'/\gamma_w \) is the critical hydraulic gradient (Terzaghi) and \( i_{exit} = \Delta H/(2D) \) is the exit gradient at the seepage face.
Design guidance typically requires \( FS_{p1} \ge 1.5 \).
References: Terzaghi (1943), Theoretical Soil Mechanics; USACE EM 1110-2-1901
This formulation reflects seepage path length considerations based on classical creep theory developed by Lane (1935). It represents a simplified expression of weighted seepage path resistance.
Typical design requirement: \( FS_{p2} \ge 2.0 \).
References: Lane (1935), "Security from Under-Seepage – Masonry Dams on Earth Foundations"; USACE EM 1110-2-1913
These formulations assume steady-state seepage and homogeneous soil conditions. They represent simplified engineering design checks and are not substitutes for fully coupled transient finite element seepage analysis.
Return period is a hazard level concept used to describe the probability of exceedance within a time window (e.g., 50 years). In geotechnical / levee practice, DBE is often tied to serviceability checks, while MCE is commonly used for liquefaction-triggering (extreme event) checks.
| Return Period | Probability (50 years) | Engineering term | Use case (geotechnical / levee) |
|---|---|---|---|
| 475 years | 10% in 50 years | DBE (Design Basis Earthquake) | General building / serviceability limit state. In this level, levees may be damaged but should not collapse; basic flood protection function must be maintained. Often used for settlement checks. |
| 2475 years (default) | 2% in 50 years | MCE (Maximum Considered Earthquake) | Critical infrastructure / ultimate limit state. This is commonly used for liquefaction analysis. The goal is to prevent catastrophic levee breach under extreme earthquake loading. |
The options below combine the design code basis (for PGA via USGS design-maps) and the NSHMP hazard disaggregation model (for Mw via NSHMP disagg).
The SPT data imported from DIGGS borehole logs may not be sufficient for a reliable liquefaction triggering analysis. Some boreholes may contain only a single SPT record, while others may include multiple tests at various depths. Liquefaction evaluation typically requires SPT measurements at several depths within the potentially liquefiable strata, along with corresponding fines content (FC%) data to perform proper corrections.
Users are responsible for reviewing the completeness, quality, and suitability of the available SPT data before performing liquefaction calculations. Engineering judgment should be applied to determine whether the data coverage and soil characterization are adequate for analysis.
DIGGS XML may not contain soil strength parameters such as cohesion (c), friction angle (φ), or undrained shear strength (Su). Data imported from DIGGS typically provides stratigraphy (depth, soil type, unit weight) but often omits c, φ, and Su.
Engineers must review and fill in the strength parameters (c′, φ′, Su/σ′v) in the stratigraphic table as required for the analysis. Do not rely on DIGGS import alone for these values.
Borehole data from DIGGS XML may not include soil strength parameters (e.g. Su, c′, φ′). Imported layers often provide depth, soil type, and unit weight only.
Users should review and judge strength values or derive them (e.g. from SPT-N correlations) as needed. Do not rely on DIGGS import alone for bearing capacity analysis.
m (metric) or ft (imperial)qc, fs: stress units kPa (metric) or tsf (imperial)u₂: water head (length) m (metric) or ft (imperial). Internally converted to pore pressure for qt correction.depth_m = depth_ft × 0.3048qc_kPa = qc_tsf × 95.7605, fs_kPa = fs_tsf × 95.7605u2_head_m = u2_ft × 0.3048u2_kPa = u2_head_m × γw, where γw = 9.81 kN/m³ (and 1 kN/m² = 1 kPa)
qt = qc + (1 − an) × u2an is net area ratio (default 0.80), and u2 is pore pressure converted from head.
σv0(z) = ∫ γ(z) dz
u0(z) = max(0, (z − GWL) × γw)
σ′v0(z) = σv0(z) − u0(z)
Fr = (fs / (qt − σv0)) × 100%Qt = (qt − σv0) / σ′v0Ic = √[(3.47 − log10(Qt))² + (log10(Fr) + 1.22)²]
Qt.
It uses an iterative procedure to compute Qtn (and a derived Ic) with a stress exponent n that depends on Ic and stress level:
Cn = (Pa / σ′v0)n, capped (typ. ≤ 1.7)Qtn = ((qt − σ′v0) / Pa) × Cn (implementation form; Pa = 101.325 kPa)Ic = √[(3.47 − log10(Qtn))² + (1.22 + log10(Fr))²]n = clamp(0.381 Ic + 0.05 (σ′v0/Pa) − 0.15, 0.5, 1.0)n stabilizes.
Kc(Ic) polynomial (for sand-like ranges), producing:
Qtn,cs = Qtn × Kc
Qtn_cs.
α = −1.012 − 1.126 sin(z/11.73 + 5.133)β = 0.106 + 0.118 sin(z/11.28 + 5.142)rd = exp(α + β Mw), capped at 1.0
CSR = 0.65 × PGA × (σv0 / σ′v0,design) × rd
CRR7.5 = exp( Q/113 + (Q/1000)² − (Q/140)³ + (Q/12500)⁴ − 2.8 )Q is the clean-sand equivalent normalized resistance used by the BI2014 implementation (i.e., Qtn,cs / Qtn_cs in the output).
MSF = 6.9 exp(−Mw/4) − 0.058, clipped to [1.0, 1.8]
Kσ = 1.0 if σ′v0,design ≤ Pa, else Kσ = 1.0 − 0.3 ln(σ′v0,design / Pa)Pa = 101.325 kPa.
FS = (CRR7.5 × MSF × Kσ) / CSR
FS < 1 (sand-like), the tool estimates strain as a function of Q and FS, then computes layer settlement:
s(z) = (strain% / 100) × Δz, and total settlement is the sum over depth.