Rock Quality Designation (RQD) Weighted Joint Density (wJd) method

This document details Datarock’s product RQD - Weighted Joint Density method.

Background

It is commonly known that datasets logged from drill core are influenced by the direction of the drilling with respect to the features of interest.

For example, if drilling is conducted parallel to the common direction of jointing, an RQD measurement will tend to be higher than if it is perpendicular to the direction of jointing.

Datarock has developed it’s Weighted Joint Density product (see wJd product description for details) to assist with this, and is furthering this work by developing this RQD Weighted Joint Density (RQD_wJd) method.

This example shown below by Palmström et al shows an example of the increased consistency of RQD_wJd over the traditional RQD in the situation where drilling direction is changed.

These comparisons show that RQD_wJd provides a different perspective on rock quality, which could be more representative of the actual conditions, especially in complex geological settings where joint orientation plays a significant role.

Literature

This product is based on the following literature: 

Dependent Models

The outputs of the following models are used:

Data Processing

To compute the Rock Quality Designation based on Weighted Joint Density (RQD_wJd), as detailed in "Practical Investigations on Use of Weighted Joint Density to Decrease the Limitations of RQD Measurement" by M. Haftani & A. Mehinrad (2015), the following procedure is outlined:

Measure the Weighted Joint Density

Take the results of Datarock’s Weighted Joint Density (see product description for details).

A summary of the steps are here:

• Take the output of the fracture detection model, “simple” classes only

• Run a segmentation model to extract the fracture profile

• Measure the angle of each fracture with respect to the core axis

• For a given interval, calculate the Weighted Joint Density

where

L = length of the measured section along the core

δ = the intersection angle, the angle between the drill core and the individual joint

This formula accounts for the frequency and orientation of joints within the rock mass. The summation (∑_​) runs over all the joints you have in your core section.

Calculate RQD_wJd

Use the formula:

This formula calculates the Rock Quality Designation (RQD) value derived from the Weighted Joint Density (wJd), offering a numerical assessment of rock quality. Generally, higher RQD_wJd values signify superior rock quality.

Product Configuration Options

There are no configuration aspects to this product.

Output Data

Default interval length: 1.0m

Customisable interval available: Yes

User Data

User data may be provided to the Datarock team via csv in the following format:

·       HoleID_sampling_intervals_rqd_wjd.csv

CSV file to contain the following headers:

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_HoleID_rqd_wjd_1m.csv

• ProjectID_HoleID_rqd_wjd_by_user_intervals.csv

Both CSVs contain the following headers:

*Only included if project depths are in feet.

Product Limitations