Source: https://guthlabs.ai/docs/instruments/soil-bearing-capacity-terzaghi-simplified/implementation/

instrument implementation / implementation-contract

# Soil Bearing Capacity — Terzaghi Simplified implementation

A source-bound implementation contract for Soil Bearing Capacity — Terzaghi Simplified; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-107

**Effect**: Computation or source lookup only

## Input and validation requirements

The allowable-capacity calculation is undefined when FS=0, so the instrument must reject that input. The specification also leaves depth/surcharge sign conventions and factor-table regime handling insufficiently explicit, creating additional hazard potential.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "c_kPa": 25,
    "phi_deg": 0,
    "depth_m": 1.5,
    "B_m": 2,
    "gamma_kN_m3": 18,
    "FS": 3
  },
  "expected_outputs": {
    "qu_kPa": 169.5,
    "qallow_kPa": 56.5
  },
  "reference_data": {
    "phi_deg": 0,
    "Nc": 5.7,
    "Nq": 1,
    "N_gamma": 0,
    "source_convention": "Widely tabulated standard value: conventional Terzaghi strip-footing bearing-capacity-factor table"
  },
  "working": "q=γDf=18×1.5=27 kPa.\nqu=cNc+qNq+0.5γBNγ\n=25×5.7+27×1.0+0.5×18×2×0\n=142.5+27+0\n=169.5 kPa.\nqallow=qu/FS=169.5/3=56.5 kPa.\nThe φ=0 row is used exactly: Nc=5.7, Nq=1.0, Nγ=0.0."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/soil-bearing-capacity-terzaghi-simplified/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/soil-bearing-capacity-terzaghi-simplified/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/soil-bearing-capacity-terzaghi-simplified/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`