Trimble GCS900 grade control system increases accuracy and eliminates the need for manual staking, improving overall efficiency by an estimated 60%

The construction of the 105 kilometer HuNan LiCha highway in China spans four lanes and involves moving 20.83 million cubic meters of earth. Managed by the HuNan LiCha Highway Development company, the highway goes from LiLin to LiuYang, ends near LiLin Highway, and crosses LiLin City, Mu Town, and ChaLin Town. During the construction of the roadway the team was primarily using manual staking methods for its excavation and grading work.

This involved the survey crew establishing horizontal and vertical controls and running preliminary lines across the project. This method proved problematic when line and grade stakes were not set at the right place, or at the right time. As a result there were frequent delays. Repeated changes in grade and alignment also prompted revisions to the stakeout, causing lengthy slowdowns. Overall, these manual staking methods proved to be time consuming and have a low level of reliability and accuracy. Faced with a tight project deadline, the project owner turned to its Trimble dealer, SITECH® South China, for help.  

The project owner selected the Trimble® GCS900 Grade Control System with Trimble Universal Total Station. Used on a motor grader to start, the Trimble GCS900 system is a full 3D control system that puts the site plan - design surfaces, grades and alignments - inside the cab. On the HuNan LiCha highway project site, the Universal Total Station provided the exact position, accurate cross slope, and heading of the blade. This system was selected because it provides extreme accuracy for lift and layer control and material monitoring. 

The GCS900 Grade Control System on-board computer uses this position information and compares it to the design elevation to compute cut or fill to grade levels. This information displays on the control box screen in plan, profile, cross-section view, or text. 

The cut/fill data is also used to drive the valves for automatic blade control; data is passed to the GCS900 lightbars, providing additional visual guidance to the operator. The grader operator believes the displays in the Trimble Grade Control System are intuitive and simple to use, which maximizes operator productivity.

“The display in the cab clearly shows the grade, design elevation and current elevation and positions the blade as needed,” he said. “Previously, it would take about 12 days to achieve the finished grade to the design requirements, and with Trimble grade control it was completed easily in a few hours.” 

 He asserts that with Trimble machine control he can achieve finish grade to millimeter accuracy much more quickly― and with fewer passes― than traditional staking methods. 

“The team can achieve accurate fine grading, without the need for manual stakeout,” said the SITECH South Dealer.  “It’s much better than traditional methods.”

By maintaining tight tolerances, GCS900 results in higher quality work. And, because finished grade materials can be placed more accurately, with minimal rework, the team realized lower material costs. 

Li Gong, the engineer responsible for technical guidance on the project site believes that the Trimble GCS900 grade control system offers significant advantages over manual staking and grading practices. The Trimble system has eliminated the chance for human error while staking. In addition, fewer surveyors are needed which reduces labor and management costs. 

Li Gong also appreciates the flexibility of the GCS900 system because it can be moved from the grader to the excavator, as needed. While the system was primarily used on a motor grader it can also be used on the excavator, bulldozer, compactor, scrapers, trimmer, and milling machines. He is confident the technology ensures the quality of construction and effectively shortens the construction period.

“The owner selected the total station-based Trimble GSC900 Grade Control System for better quality management and accelerated construction of the highway,” said Li Gong. “We estimate we’ve been able to improve efficiency across the project by 60%.”