Dirt simple paving – from string lines to complete 3D machine control solution

Author: Richard Davies

Worldwide, the number of journeys taken by air has increased exponentially over the past 70 years. According to Flight 24, in a single day over 230,000 commercial flights flying across the sky. A recent study by  E. Mazareanu estimates the number of passengers travelling on scheduled flights to be over 4.72 billion in 2020; it is around 137 per cent higher than in 2004.

The United Arab Emirates (UAE) in particular is fast becoming a significant hub for air travel, with both Abu Dhabi and Dubai International Airports competing for a growing connections market. The level of infrastructure needed to support this scale of operation is substantial. It is vital that it is constructed to the highest standards and that any downtime is limited when maintenance is required.

Al Nisr, a construction company based in the UAE, is a world leader in the construction of airfields and supporting infrastructure. The company is experiencing rapid growth and believes that investing in technology is vital when competing for complex contracts, particularly those that involve the paving of runways or aprons. The company has previously been involved with major UAE projects at Abu Dhabi International Airport, Al Maktoum International Airport, Sharjah International Airport, Al Bateen Executive Airport, Al Fujairah International Airport, and many military airbases across the UAE.

From traditional string line method to complete 3D paving solution

When paving infrastructure as important as runways and airfield aprons, Al Nisr aims to lay a runway to a tolerance of 5 millimetres, meaning 5 mm or less variation in the thickness, the height of the surface. Traditionally, they had utilised string line methodology to achieve this accuracy in their paving work, using manually laid out strings staked into the ground to guide the thickness and level of the asphalt being laid. This string line methodology can impact the level of accuracy and productivity, as highlighted by Al Nisr’s general manager, Eng., Orwa Alward Zaidan:

“We were using string lines – this limited the number of trucks that could come and drop materials. Sometimes people can hit the string lines, and this causes problems. Concrete is laid at night, and the survey of the site is carried out in the morning, so if the string is hit in the evening, it delays the project until the next morning. String is also sometimes not accurate and can experience sag – this can have a negative impact on the accuracy of the surface. With string, we could originally only pave 300m lengths at a time.”

With several significant upcoming projects such as a new airfield operated by Etihad Airways in Abu Dhabi and a military airfield, Al Nisr invested in a Leica iCON Pave Concrete machine control system from Leica Geosystems, part of Hexagon, to improve their efficiency and accuracy in work. The company was already aware of Leica Geosystems’ easy-to-use solutions, as one of their engineers had used the system in the UK and was impressed with the performance, understanding that it represented a complete solution for 3D asphalt paving. In addition, Al Nisr had previously used a variety of survey solutions from Leica Geosystems, including Leica TS9 and TPS1200 total stations, along with Leica Viva GS14 GNSS smart antennas. They were always happy with the usability and reliability of this survey equipment, so it made sense to invest in Leica Geosystems’ machine control solutions.

Achieving high-accuracy with stringless paving

Machine control systems save time and costs for a variety of heavy construction applications and are used in paving applications to avoid dependency on string lines, making work easier for operators and contractors, while reducing costs. Stringless concrete paving also increases the consistency and quality of the finished surface.

The Leica iCON pave concrete system purchased by Al Nisr consists of the rugged, shock and waterproof Leica MCP80 control panel, Leica iCR80 or TS16 total stations, and two Leica MPR122 360° prisms for guidance, all supported by Leica MC1 software, the all-in-one software platform for machine control. When using the system, the operators from Al Nir found the graphical interface intuitive and uncluttered, allowing them to focus on the job at hand and complete work quickly with the desired precision. Leica ConX is a cloud-based solution and web interface allowing customers to visualise and validate localised reference models, survey data and constructed data, with powerful analysis tools for monitoring and reporting site productivity. Al Nisr found this feature particularly helpful, as it allowed their chief surveyor to accurately visualise progress on site from the comfort of his office.

Before paving work began, a survey was completed using Leica GS14 GNSS smart antenna and total station solutions from Leica Geosystems. Autodesk AutoCAD Civil 3D software was used to make a model of the site, before converting into an XML file and then simply uploading it directly to the pavers. Leica iCONstruct Field Simulator was used to ensure everything was correct before work began. Once sections of paving were completed, as-built checks were carried out again using Leica Geosystems GNSS equipment, along with Leica NA2 automatic levels.

Thanks to the easy integration and interoperability of the various software and hardware solutions the Hexagon portfolio offers, Al Nisr was able to move from traditional workflows toward a more connected, digitised construction site.

On-going on-site support and training from Leica Geosystems

The installation of the system was supported locally by dedicated machine control staff from Leica Geosystems and their local distribution partner, GECO Engineering. Al Nisr staff needed training – Leica Geosystems staff visited and sat with the engineers and all other staff involved with the project, to ensure they were comfortable with the system. On-going support was also provided during the project.

Laying runways and aprons using GOMACO GHP2800 and GP2400 pavers, the system has provided a wide variety of benefits to Al Nisr, efficiency being the main one. Originally, a paver had a run of 300 meters linear per night but now can do 900 m linear per night or nearly 2000 cubic metres per night. In addition, with this technology, the role of surveyors is now easier and safer. Pave patterns and models developed in the office can directly be uploaded to the pavers without having to knock in any pins for string lines. Thanks to the increased visibility offered by ConX, all stakeholders can now look at the project and say, with confidence, that it will be completed significantly faster than before.

The benefits of using machine control are clear to chief surveyor, Arshad Mahmood:

“Everything is nice, we really like the system! In UAE, this system helps us to lead the market – we can now look at a project and say it can be completed in a much shorter time. I would say that we see up to three times more productivity than when we use a regular system”.

Overperforming expected deadlines with machine control

Initial calculations suggested that the Abu Dhabi airfield project could take up to 12 months, yet utilising machine control from Leica Geosystems, it took six months. With large infrastructure projects such as airfields, contractors want to complete well within deadline as this allows them to avoid significant financial punishments, and move onto other jobs.

Leveraging the wide-range products and brands of Hexagon’s heavy construction portfolio, Al Nisr is proud to be the pioneer of machine control for airfields in the United Arab Emirates. The approach increases the company’s performance, improves its reputation, and helps the business win more work.