Raumati Escarpment – Case Study

Site Owner – Kiwirail
Lead Engineer – WSP Opus

Overview:

New Zealand’s main trunk railway line runs north out of Wellington past the Raumati Escarpment where recent slippages began occurring towards the main line. Kiwirail commission WSP OPUS to monitor this site for risk of landslide. Led by Senior Geotechnical Engineer David Stewart, WSP Opus identified ten sites that were suitable for daily measurement.

Installation:

Over the course of the day, the AccuMM sensors and base station were installed along suitable and secure (i.e. to prevent vandalism) points. The site had good cellular coverage enabling data transfer to the cloud and despite the large amounts of shrubs, most sensors were able to communicate to the base station via a 2.4GHz frequency. Only one sensor required a repeater to help relay the data to the base station.

Monitoring:

Raw GNSS data is collected by our sensor network and transmitted to our cloud server to analyse the relative position of each sensor in the North, East and Up position. Data from the sensor network is then integrated into WSP Opus’ internal reporting and alert solution. To test the robustness of the solution, WSP Opus moved two sensors by 230mm and 660mm respectively. These changes were picked up within 24 hours in the data.

The value of AccuMM

The site has some boreholes with inclinometers installed in the landslide to allow WSP Opus to measure the depth of movement. Inclinometers are useful as they help determine the appropriate method of remediation. However, field staff have to return regularly to see if the slope has moved and distorted the bore hole. With AccuMM sensors installed on site, WSP Opus can now remotely monitor and assess when the movement occurred – this enables better planning for appropriate site visits.

This reduces the cost of monitoring by reducing the need for frequent site visits and provides rich continuous data that can be used to assess risky sites.