Joint Roughness Coefficient (JRC) Proxy

This document details Datarock’s product Joint Roughness Coefficient (JRC) Proxy.

Literature

This product is based on the following literature:

Title	Author	Year
The Shear Strength of Rock Joints in Theory and Practice	Barton & Choubey	1976
A new method estimating the 2D Joint Roughness Coefficient for discontinuity surfaces in rock masses	Zhang et al	2014

Dependent Models

The outputs of the following models are used:

Model Name	Model Type
Fracture Detection and Classification	Object Detection
Drillers Break	Object Detection
Fracture Mask	Instance Segmentation

Data Processing

The following steps are taken to determine the JRC:

Take the output of the fracture detection model, “simple” classes only
Run a segmentation model predicting the fracture itself, then post process into a binary mask/overlay. The edges of this overlay are known as skeletons.
Fit an ellipse to left and right skeletons
Check for core neatness: plot each ellipse on stereonet, if tight fit, proceed to the next step. If not, discard this joint for measurement.
Check for neatness of fit of the ellipse to the skeleton. If outside of threshold, do not proceed.
Straighten out profile of ellipse, fracture profile interface

jrc-1

7. Calculate the JRC_median, JRC_lower_bound, JRC_upper_bound for each. This provides a score from 0-20.

jrc-2

Product Configuration Options

There are no configuration aspects to this product.

Output Data

Fracture point data

User Data

Not currently able to upload to the platform.

Data Output

Results from this product is delivered in a batch nature.

Integration of the required technologies into Datarock production is ongoing.

The available CSV files include the following:

ProjectID_JRC_3m.csv

File Header	Description
hole_id	Customer’s Hole ID
depth_m	Depth of fracture (metres)
depth_ft	Depth of fracture (feet)
depth_from_m	From depth for the fracture detection bounding box (metres)
depth_to_m	To depth for the fracture detection bounding box (metres)
depth_from_ft	From depth for the fracture detection bounding box (feet)
depth_to_ft	To depth for the fracture detection bounding box (feet)
shape_status	Success/failure of ellipse fitting. Includes reason if failed.
jrc_status	Success/failure of JRC measurement. Includes reason if failed.
jrc_left_s	Left side of fracture: suggested (median) JRC measurement
jrc_left_u	Left side of fracture: upper bound JRC measurement. The statistical upper bound of the potential range of JRC values based on this method.
jrc_left_l	Left side of fracture: lower bound JRC measurement. The statistical lower bound of the potential range of JRC values based on this method.
jrc_right_s	Right side of fracture: suggested (median) JRC measurement
jrc_right_u	Right side of fracture: upper bound JRC measurement. The statistical upper bound of the potential range of JRC values based on this method.
jrc_right_l	Right side of fracture: lower bound JRC measurement. The statistical lower bound of the potential range of JRC values based on this method.
jrc_left_error	Fit score of the ellipse fitting to the left skeleton.
jrc_right_error	Fit score of the ellipse fitting to the right skeleton.
selected_side	The selected side of the fracture for reporting final JRC measurements.
JRC	The suggested JRC measurement of the selected side of the fracture.

Product Limitations

Limitations	Comments
Measurement on “simple” fractures only	This method is limited to fractures that have one interface only, as we need a clear interface to measure. There may be intervals of broken rock that have different JRC values
Analysing interface of fracture with edge of core	The nature of this method relies on a direct correlation between a fracture’s internal roughness and the appearance of its interface with the circumference of the core. A comparison with logged data across the customer’s range of lithology is required.

Document Version

Version	Date	Author	Rationale
1	7 Sep 2022	S Johnson	Initial release
2	29 January 2024	S Johnson	Updated to include depth in feet