GEO-Instruments have been providing a multi-part structural monitoring scheme for a key reservoir dam in Derbyshire.
Throughout the year, Survey and Site Engineering teams from GEO-Instruments have been working at the site alongside colleagues from Keller UK, who have been carrying out piling works to strengthen the structure of the Dam.
A crucial infrastructure asset since its construction in the 19th century the dam is an example of a Bateman Embankment Dam and part of a series of reservoirs which collectively help regulate water levels on the Etherow river. The system of dams has an important role in ensuring a reliable water supply to the urban areas of Greater Manchester.
In addition to its functional role, this reservoir also plays a part in the local ecosystem and leisure industry, providing a habitat for wildlife as well as a popular spot for walking and sailing.
The dam was constructed more than 150 years ago and has been subject to many decades of wear and tear and cycles of maintenance.
The ground improvement works undertaken by Keller are part of an improvement scheme that will help safeguard the integrity of the dam, ensuring the long-term safety and effectiveness of the structure.
Keller have installed a series of piles anchored in competent rock below the dam, along with ground anchors and a capping beam that ties all the strengthening measures together.
The key aims of the works are to strengthen the ground and stabilize movement, repairing long-term damage and protecting against future deterioration of the structure.
To supplement the on-going historical monitoring of the dam, GEO-Instruments are implementing multiple types of automated and manual monitoring regimes during the structural improvements as well as providing setting out services for the ground engineering works.
Manual levelling
Manual levelling offers precise, long-term data on the vertical movement of the structure.
Surveyors take precise measurements of the height of the dam's surface, calculating differential settlement. These measurements are taken at dozens of regularly spaced, fixed points along the structure. Regular surveys give a consistent insight into the movement of the dam over time.
The technique is simple but effective, offering high accuracy and reliability, making it an indispensable part of the works program.
Noise & Vibration monitoring
The inclusion of vibration monitoring in the scheme allows the team to assess the impact of ongoing site works on the dam’s structure.
Before piling works began, a triaxial geophone vibration sensor was installed on the downstream side of the dam. Installed non-intrusively using a mounting plate, this Geophone will accurately measure vibration which may be transferred to buildings and structures. These instruments are highly sensitive to all sources of vibration but are particularly useful for measuring the impact of ground works in this application.
Two S50 sound level meters have been set up on either side of the valley to monitor the noise levels (average LAeq) generated by the site works and the potential impact on the surrounding environment. This is particularly important for this site due to its location within a UK national park.
All noise and vibration sensors are battery powered and wireless, providing continuous, unattended monitoring. The systems are configured to British Standards and can be accessed remotely to monitor their status and battery voltages.
Inclinometers
A series of In-Place Inclinometers (IPIs) were installed into selected piles to provide continuous, high-frequency data to monitor the lateral movement and structural integrity of the structure and surrounding ground.
This will allow site teams to assess where potential movement is occurring and determine the effectiveness of the remedial works.
The IPIs were designed with 1-metre and 2-metre segments to cost-effectively give the required resolution of measurement at specific depths.
All monitoring data is automatically collected and transmitted via a wireless gateway to GEO server logger and presented on GEO-Instruments’ QuickView online platform.
Setting Out
GEO-Instruments’ site engineering team were responsible for setting-out of pile locations and determining anchor positions, providing essential information to the drilling team.
Using a robotic total station, the engineers ensured that rigs were correctly aligned by precisely measuring locations and angles of drilling positions.
The site engineering team has extensive experience working alongside Keller and uses the latest technology to quickly and efficiently support ground improvement works.
Projects like this are essential for the continued operation of older structures that are depended upon by local towns and cities.
The work done by Keller and GEO-Instruments will help maintain this important piece of infrastructure and ensure that the reservoir remains a reliable resource for future generations.
Read more about our projects working alongside Keller UK.