Rock Fence Monitoring

Introduction

Rockfall is the movement of rock of any size from a cliff or other slope so steep that the mass continues to move down the slope with considerable speed and force. Rockfall typically is a high-risk event that occurs suddenly and very rapidly. Rockfall can have many causes, ranging from geology (such as fractured rock, slope failures, or excavations) to climate and hydrology (rain and debris flow) as well as blasting and vibration, among other factors.

Mitigating the risks of rockfall includes active monitoring (usually visual), relocation, stabilization and protection. Catchment fences and rockfall barriers often provide viable protection when other methods are unavailable. Rock fences themselves require constant monitoring to ensure that their protection isn’t downgraded over time by repeated rockfall.

Solutions

Canary Systems® has designed an automated remote monitoring Rock Fence Monitoring system allowing for 24/7 surveillance of long stretches of rock barriers. Consisting of a 2g tri-axial accelerometer sensor module attached to the supporting cable ropes of the fence or barrier, and a solar or battery powered data acquisition enclosure (MLDAQ). The system is capable of self-sufficient operation for long periods of time in adverse conditions and remote areas without human supervision. The signal summing electronics and amplifier allow for mounting of the sensor assembly in any orientation while providing high sensitivity.

The accelerometer constantly monitors the barrier in low power mode. When a rock or rocks hit the fence, a high-frequency vibration event is triggered, recorded and transmitted to the data enclosure. Proper calibration and use of algorithms allow estimation of size, force and location of the rockfall that occurred. The system can be configured to send out notifications and alerts automatically to appropriate staff. Simple event triggers are supported as well as complex notification schemas based on frequency, force and location of impacts.

Active Monitoring

2g tri-axial accelerometer sensor detects rock impacts

Mitigate Risks

24/7 surveillance with data acquisition enclosure (MLDAQ) in battery or solar power mode

Automated Alerts

Configure alert notifications to be sent to appropriate staff

Case Study

LARGE MINE IN ASIA

The Civil Geotech group at a large mine in Asia is monitoring rockfall along a main access road in the mountains. Rockfall poses a constant risk due to the extremely steep cliffs as well as frequent high-intensity rainfall, leading to numerous road closures. Landslides occur often and with little to no warning. An automated early warning system is required to improve reaction times for evacuations and road closures to prevent loss of life and material.

Canary Systems deployed the Rock Fence Monitoring system at multiple locations along the road. Data is being fed into the master database containing other geotechnical project data from the area and the mine. Alerts and notifications are triggered based on frequency and severity of events, indicating building risk of landslides or increased debris flow.