How to make HS2 (settlement prediction) 80% faster

There are around 90km of earthworks (embankments and cuttings) across Phase 1 of HS2 – Europe’s largest infrastructure project – between London and the West Midlands, which is being designed by the Mott MacDonald-Systra Design Joint Venture. Following construction, embankments settle as earth compacts; cuttings heave as newly exposed ground decompresses. The extent and rate of settlement or heave is affected by soil type, embankment height or cutting depth. Geological and topographical variation means that the amount and speed of settlement of every earthwork asset differs.

HS2 will ultimately connect London with Glasgow and Edinburgh. Construction is under way on phases 1 and 2a

Before slab track, electrification and signalling equipment are installed, the embankments/cuttings must all but stop settling. Depending on the asset, as little as 5mm and a maximum of 60mm settlement/heave is permitted over the railway’s 120-year design life. Providing that assurance requires the full length of each earthwork to be monitored for 18 months. Many thousands of measurements must be logged and analysed, tracking settlement/heave to the point it slows almost to a stop. Using traditional methods, the task would have required the equivalent of two engineers full-time for nine months.

We saw the opportunity to radically improve time efficiency by automating some of the most time-intensive activities. Our in-house productivity team developed a digital solution with the aim of unlocking time and cost savings on Phase 1 earthworks.

Embankment adjoining the Marston Box rail over road bridge, north of Birmingham

A 3000-hour challenge

In total, main works contractor Balfour Beatty-Vinci joint venture (BBV) will install around 2000 ground movement monitoring points at intervals of between 5m and 50m. We specified the instrumentation and locations, with smaller spacing at sensitive points on the route where we expected more earth movement, such as close to the ends of embankments and at transitional points on the route, where an embankment meets a cutting, bridge or viaduct. Settlement/heave data from the measuring instruments is being monitored for six months, with readings taken three times a week to begin with, falling to twice a week when earthworks show less movement.

Monitoring data is traditionally entered into a spreadsheet to produce settlement curves – trend lines showing the rate of settlement, from which we can project future settlement using tried and tested industry formulas. Processing and interpreting the vast amounts of data using the traditional method would have taken 3000 hours.

2000 ground movement monitoring points being installed

Settlement is monitored using instruments installed in different locations on an embankment – in the crest, at the toe and underneath

Capability at the push of a button

We used the programming language Python to create the Instrumentation Monitoring Interpretation Tool for Embankments, or IMITE. BBV uploads manual and remote readings to its cloud-based data management system. From there, IMITE imports this data and automatically plots it onto ground movement curves. IMITE also interprets the data and makes long-term settlement/heave predictions using geotechnical formulas that have been in use internationally for several decades, calibrating it against a wealth of past projects.

Predicted ground movements have been extensively cross-checked against real measurements and fully trained engineers also rigorously check the data to assure that the outputs are reliable.

Unlike the traditional spreadsheet, IMITE has a graphic interface that is easy to use, with the ability to view and isolate ground movement information for each individual earthwork asset, across the entire length of the line.

From two hours to 10 minutes

One of our main aims was to reduce the amount of time talented engineers spend on repetitive activities that are essential, yet underuse their potential value. Automating repetitive tasks frees them to apply their problem-solving and creativity elsewhere on the project. We have consequently shown that IMITE cuts the time spent on plotting and interpreting each dataset from one hour for an experienced engineer or two hours for a graduate, to just 10 minutes.

10 minutes for monitoring job that used to take 1-2 hours

IMITE has been proved on Phase 1 and is now ready for use on further HS2 work, as well as other construction projects where settlement monitoring is needed. Its success has catalysed the development of additional geotechnical tools, such as the Deep Excavation Instrumentation Interpretation Tool (DEIIT), which helps to automate interpretation of the movement of walls in deep excavations such those dug for underground stations.

Both are practical examples of digital innovation applied to radically improve common industry processes, delivering better quality at reduced cost for clients, alleviating the ongoing skills shortage by enabling engineers to use time more efficiently, and ultimately providing better value to infrastructure users.