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Cone Penetration Test (CPT) Friction Ratio (R_f) & Robertson Soil Behavior Type Calculator

Easily calculate and compute cone penetration test (cpt) friction ratio (r_f) & robertson soil behavior type calculator with accurate equations, live formulas, and expert guidance.

Measured tip resistance from electric penetrometer cone.

Friction along cylindrical sleeve behind tip.

Total vertical overburden pressure at test depth.

Vertical effective stress.

Calculated Result
2.43 %

Friction Ratio (R_f)

Friction Ratio (R_f)

2.43 %

Friction Ratio Percent Rf

2.43

Soil Behavior Type Index Ic

2.38

Robertson Soil Classification

Zone 4: Clayey Silt to Silty Sand

Normalized Cone Resistance Qt

52.4

2.43 — %

Calculation Breakdown

  1. Applied FormulaClassifies subsurface stratigraphic soil behavior types (SBT) and estimates undrained shear strength (su) from Cone Penetration Test tip resistance and sleeve friction readings.Q_t = \frac{q_c - \sigma_{v0}}{\sigma'_{v0}}, \quad F_r = \frac{f_s}{q_c - \sigma_{v0}}\times 100\%, \quad s_u = \frac{q_t - \sigma_{v0}}{N_{kt}}

CPT Soil Classification Metric Output

Interactive visualization based on your current inputs

Calculated Value
0.00.61.21.82.4Friction Ratio (R_f)

What Is the Cone Penetration Test (CPT) Friction Ratio (R_f) & Robertson Soil Behavior Type Calculator?

This tool computes cone penetration test (cpt) friction ratio (r_f) & robertson soil behavior type calculator with high precision arithmetic.

How Does the Cone Penetration Test (CPT) Friction Ratio (R_f) & Robertson Soil Behavior Type Calculator Work?

Classifies subsurface stratigraphic soil behavior types (SBT) and estimates undrained shear strength (su) from Cone Penetration Test tip resistance and sleeve friction readings.

Cone Penetration Test (CPT) Friction Ratio (R_f) & Robertson Soil Behavior Type Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

Qt=qc−σv0σv0′,Fr=fsqc−σv0×100%,su=qt−σv0NktQ_t = \frac{q_c - \sigma_{v0}}{\sigma'_{v0}}, \quad F_r = \frac{f_s}{q_c - \sigma_{v0}}\times 100\%, \quad s_u = \frac{q_t - \sigma_{v0}}{N_{kt}}

Classifies subsurface stratigraphic soil behavior types (SBT) and estimates undrained shear strength (su) from Cone Penetration Test tip resistance and sleeve friction readings.

How to Use the Cone Penetration Test (CPT) Friction Ratio (R_f) & Robertson Soil Behavior Type Calculator

  1. Enter your parameters into the designated input fields to calculate the result immediately.

Step-by-Step Example Calculation

Cone Penetration Test (CPT) Friction Ratio (R_f) & Robertson Soil Behavior Type Calculator Example

Input Values:

measuredConeResistanceQcMpa:3.5
sleeveFrictionFsKpa:85
totalOverburdenStressSigmaV0Kpa:95
effectiveOverburdenStressSigmaV0PrimeKpa:65
Worked Steps: Sample evaluation based on standard reference conditions.

Understanding Your Result

The calculated primary figure indicates the optimal or required %.

Factors That Affect the Result

  • Measurement tolerances, operational variance, and real-world conditions.

When Should You Use This Calculator?

  • Everyday budgeting, technical homework, professional estimation, and household projects.

Assumptions & Limitations

  • Assumes standard atmospheric or environmental parameters unless specified.

Frequently Asked Questions

Calculation Accuracy & Reference Note

Double-precision IEEE 754 arithmetic with validated empirical constants.

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