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Reading the interpretation

Design and average CBR, the profile chart, detected layers and the correlation caution.

The right-hand panel interprets your readings as you enter them.

Live interpretation

The basis is stated at the top: Legacy TRL ORN8 interpretation.

Value	Meaning
Design CBR	The governing value for design
Average CBR	Mean across the profile
Penetration	Total depth penetrated
Total blows	Blows delivered

Design CBR is normally lower than Average CBR, because design takes the governing weak layer rather than the mean. Use Design CBR for pavement design; Average CBR is context.

The CBR profile

A chart plotting CBR against depth on a log scale. It shows where the profile weakens and strengthens with depth — the shape matters as much as the headline number. A uniformly moderate profile and a strong crust over soft subgrade can produce a similar average and behave completely differently.

Detected layers

Below the chart, GeoCRM groups the readings into layers with a CBR for each — for example 0–150 mm, CBR 8.3% and 150–300 mm, CBR 17.3%. This is the profile reduced to design layers.

The caution

The panel carries a standing warning, and it should be read rather than dismissed:

Empirical in-situ estimate. Confirm instrument, material, moisture and correlation applicability; use laboratory CBR where specified.

DCP-derived CBR is a correlation, not a measurement. The correlation was developed for particular materials and conditions, and it does not hold everywhere — it is unreliable in coarse granular material and sensitive to moisture. Where a specification calls for laboratory CBR, a DCP result does not satisfy it. See The test method library for the laboratory test, AS 1289 6.1.1.

# Reading the interpretation

The right-hand panel interprets your readings as you enter them.

## Live interpretation

The basis is stated at the top: **Legacy TRL ORN8 interpretation**.

| Value | Meaning |
|---|---|
| **Design CBR** | The governing value for design |
| **Average CBR** | Mean across the profile |
| **Penetration** | Total depth penetrated |
| **Total blows** | Blows delivered |

**Design CBR** is normally lower than **Average CBR**, because design takes the governing weak layer rather than the mean. Use Design CBR for pavement design; Average CBR is context.

## The CBR profile

A chart plotting CBR against depth on a log scale. It shows where the profile weakens and strengthens with depth — the shape matters as much as the headline number. A uniformly moderate profile and a strong crust over soft subgrade can produce a similar average and behave completely differently.

## Detected layers

Below the chart, GeoCRM groups the readings into layers with a CBR for each — for example *0–150 mm, CBR 8.3%* and *150–300 mm, CBR 17.3%*. This is the profile reduced to design layers.

## The caution

The panel carries a standing warning, and it should be read rather than dismissed:

> Empirical in-situ estimate. Confirm instrument, material, moisture and correlation applicability; use laboratory CBR where specified.

DCP-derived CBR is a correlation, not a measurement. The correlation was developed for particular materials and conditions, and it does not hold everywhere — it is unreliable in coarse granular material and sensitive to moisture. **Where a specification calls for laboratory CBR, a DCP result does not satisfy it.** See **The test method library** for the laboratory test, AS 1289 6.1.1.