ASIMS started in 2000 as a joint initiative between MBGS and Seedsman Geotechnics Pty Ltd (SGPL) to extract quality geotechnical data from downhole geophysical logs. Interpretation and analysis of acoustic scanner, optical televiewer and sonic logs enhances the quantity and quality of geotechnical data from drill holes for more effective mine planning and civil engineering/infrastructure development.
In-house interpretation techniques have been developed in conjunction with Seedsman Geotechnics. Our skilled ASIMS geologists examine the logs using WellCAD and other software to extract only the relevant and reliable data. Resulting in a comprehensive in situ geotechnical perspective of the data, provided through ASIMS’ utilisation of SGPL geotechnical expertise.
It is never too early to collect and process quality geotechnical data!
ASIMS offers two analysis reports, the Acoustic Scanner/Optical Televiewer Report and the Sonic Log Report, which may be combined or provided separately as required:
Acoustic Scanner/Optical Televiewer Report
What is the Acoustic Scanner?
Sometimes referred to as the acoustic televiewer or ATV, the acoustic scanner is a geophysical downhole logging tool that generates a high resolution image of a drill hole wall by transmitting ultrasonic pulses and recording the amplitude and travel time of the reflected signals.
The amplitude of the reflected signal is a function of the rock properties of the drill hole wall. By interpreting the patterns of linear features in the reflected signal, it is possible to determine the orientation and type of discontinuities or defects (e.g. joints and faults) intersected within the hole.
The travel time of the reflected signal is a function of the shape of the drill hole wall, such that any wall failure is recorded. The characteristic lemon shaped failure seen in the travel time log from borehole breakout can be used to interpret the direction of principal horizontal stress.
What is the Optical Televiewer?
The optical televiewer (also known as the OTV) is a downhole logging tool that generates a continuous orientated image of the drill hole wall using an optical imaging system. Changes in lithology, structural discontinuities and possible wall failure can be identified from the image.
The optical televiewer is able to be used in air or clean water, an advantage over the acoustic scanner, which can only be used in fluid filled holes. A limitation of this tool is that borehole breakout cannot be completely resolved as the shape of the drill hole wall cannot be precisely confirmed.
The Acoustic Scanner/Optical Televiewer Report
The report provides oriented data, important for open cut and underground mine planning and development:
- Borehole breakout – providing information on principal horizontal stress direction (only applicable for the acoustic scanner)
- Fault orientation
- Discontinuity data – bedding orientations and joint/cleat set patterns
Benefits of the report
- Increased understanding and confidence in the structural model
- Information on pit wall stability or optimal longwall orientation
- Guidance for roof and rib support design and gas drainage
The Acoustic Scanner/Optical Televiewer Report – Civil/Infrastructure
ASIMS now offers a report to meet the needs of civil engineering and geotechnical companies undertaking infrastructure projects such as roadways, tunnels, dams, bridges and other construction works.
This report contains:
- Orientation of bedding, joints and faults
- Defined discontinuity sets
- Direction of principal horizontal stress from borehole breakout (only applicable for the acoustic scanner)
To download our civil focused brochure click here
What is the sonic log?
The sonic log is a downhole geophysical logging tool that provides interval transit time for the rock formation which varies depending on lithology, rock texture and porosity. It is well known that the sonic log can be used to calculate Uniaxial Compressive Strength (UCS), but it may also provide a Rock Strength Index.
What is the Rock Strength Index?
The Rock Strength Index (RSI) is a measure that seeks to examine the performance of a rock mass by normalising the UCS of the rock to the insitu vertical stress. It can be readily calculated from the density and sonic velocity geophysical logs obtained from any uncased drill hole. The RSI is an essential tool that identifies the critical zones in an underground coal mine:
- estimate the height of softening above mine roadways
- a good predictor of the need for secondary roof support
- identify zones where floor heave may develop
For more information refer to Seedsman Geotechnics’ paper: Application of the Brittle Failure Criterion to the Design of Roof Support in the Soft Rocks of Coal Mines
The Sonic Log Report
The report presents:
- Calculated Uniaxial Compressive Strength (UCS) values for the entire drill hole and immediate roof and floor intervals of coal seams
- Rock Strength Index (RSI) for immediate roof and floor intervals of coal seams
- Massive unit identification
Benefits of the report
- Information to optimise roof support and roadway design
- Assistance in planning panel width and anticipating road way trafficability