Open Cut » Rock Mechanics
A critical parameter in determining slope stability for spoil piles and tailing dams are groundwater conditions. Current technologies such as cabled or standpipe piezometers are used to collect groundwater information from spoil pile. However, this type of information is difficult to obtain due to operational (safety and integrity) and technical (drilling and reliability) issues. A new method for remotely monitoring in-situ groundwater conditions in spoil piles and tailings dumps is required. The proposed solution is to develop preliminary sensors that can measure ground water in-situ for critical parameters including movement, temperature, pressure, pH, and moisture and communicate and transmit the individual sensor's data to the surface for analysis.
The goal of this project was to deliver a prototype system of wireless, groundwater sensing tools that communicate with each other over a 100-500m distance through overburden material whilst ensuring positioning accuracy to within one metre that has been validated in the field.
The objectives of the project were to:
- Develop design requirements and criteria for a spoil and tailing dam wireless sensing system;
- Identify commercially available components and systems and industry best practices that can be implemented or used in the prototype system;
- Develop a method for data communication between the proposed sensors;
- Validate individual prototype components with field testing;
- Perform field tests to quantify battery life and the data transfer signal range through varied material types and conditions; and to
- Provide recommendations and next steps progressing the path to commercialisation with minimal technical risks.
The outcomes of this project were:
- A component lab testing prototype of the wireless ground-water monitoring tool is demonstrated, and its field-application capability mapped.
- Wireless communication technologies and sensors for water pressure, movement, temperature, pressure, and moisture were successfully validated.
- Of the pressure sensors tested, the Geokon 4500S pressure sensor is recommended due to the robustness, reliability, and accuracy performance.
- Of the temperature sensors tested, the Geokon 4500S thermocouple sensor is recommended due to the robustness, reliability, and accuracy performance.
- Based on background research a low-frequency (ELF, SLF, ULF designation) frequency-shift-keying modulation using a magnet or transmission coils are the preferred technologies for wireless communication through earth.
- Of the two wireless communications technologies above, a rotating magnetic technology was selected for the prototype build out due to the greater transmission range, and reduced power consumption.
- Communications and robustness of Elexon's Cave Tracker system was validated as a system platform via site field testing at the monitor's site. Validation characterized the performance of in different material environments to a range of 220m in overburden material, field testing of the housing to ensure that it is rugged for the intended use, and power consumption requirements for extended deployment of years. The system successfully passed all tests.
- Based on the results above, individual components of a prototype system were tested and successfully transmitted groundwater pressure and position data through a 220m communication link.