With the implementation of the water-stabilized base layer and base construction in the expansion project of the G5 Jingkun Expressway from Guangyuan to Mianyang by China Railway Fifth Bureau, key technical parameters such as paving thickness, flatness, and compaction have all met standards. The advantages of the “3D printing-style pile-free intelligent paving + unmanned compaction cluster” system have once again been validated in actual construction. This represents a highly integrated and precision-demanding pavement construction system in highway construction, breaking through industry technical bottlenecks and improving pavement construction efficiency by 30%, with flatness errors controlled within 3 millimeters, setting a new benchmark for intelligent highway construction.
What are the remarkable features of this intelligent system? How does it achieve “intelligent” precise construction? With these questions in mind, we visited the construction site of the Guangmian Expressway LM4 section to decode the “intelligent code” of pavement construction.
3D Printing Style Pile-Free Paving: Achieving Millimeter Precision in Pavement
During the construction of highways, the quality control of the geometric shape of each structural layer is limited by traditional measurement techniques, commonly using cross-section measurement methods. The lack of field data between two measurement sections fails to reflect the true geometric shape of the highway comprehensively. In traditional pavement construction, workers need to set steel piles every 10 meters on-site, and then guide the paver to level the work using hanging lines. This method not only consumes a lot of manpower but also leads to flatness errors of 2-3 centimeters due to pile position deviations and collisions. However, the 3D printing-style pile-free intelligent paving system applied by China Railway Fifth Bureau in the Guangmian Expressway LM4 section completely resolves this construction shortcoming.
① 3D Modeling: Creating a “Digital Blueprint” for the Construction Pavement
The 3D printing-style pile-free intelligent paving technology integrates optical positioning, communication, and intelligent sensing technologies to achieve automatic leveling of the paver, allowing precise control of design elevation, material thickness, and flatness during pavement construction. Before construction, technicians import the road design’s vertical and horizontal curves, cross-section, and super elevation parameters into the system to generate a three-dimensional road model. This model serves as an accurate “digital blueprint” down to the millimeter, containing elevation, slope, and coordinate information for each point, and can automatically adjust the paving thickness based on the undulations of the next structural layer: reducing the thickness in continuous raised areas and increasing it in depressed areas, eliminating factors that cause pavement unevenness from the source.
“In the past, we relied on manual calculations for slopes, which could lead to multiple errors over a 100-meter section; now the model automatically generates data with zero manual intervention throughout the process,” a technician pointed to the three-dimensional model on the screen. The model generated by the system includes accurate and detailed pile numbers, cross slopes, longitudinal slopes, coordinates, etc. (see image 2), avoiding human calculation errors and improving construction efficiency and precision. Before paving, the entire pavement is scanned with a scanner, and through point cloud processing (denoising, modeling), data analysis (elevation verification, flatness calculation, theoretical volume calculation), the material usage for each section of the road is calculated in advance, avoiding the traditional construction issues of “over-paving waste and under-paving rework.”
② Intelligent Control System: The “Smart Brain” of the Paver
The core of this system is the “trinity” control system:
Onboard part: The paver is equipped with a 3D controller, cross slope sensors, hydraulic controllers, etc., acting like “nerve endings” that perceive the machine’s posture in real-time.
External part: Two total stations act as “eyes,” using advanced imaging scanning technology, with an angle measurement accuracy of 1″, distance measurement accuracy of 2mm, scanning speed of 26,600 points/second, and a scanning distance of 600 meters. They can perform camera aiming and true color data acquisition, integrating 3D scanning with total station technology for one-click output of result data. One total station locks onto the optical target on the paver, achieving real-time positioning accuracy of 3 millimeters; the other tracks the rear prism to verify the paving elevation.
Digital construction cloud platform: Acting as the “brain,” it compares on-site data with the design model, sending adjustment commands to the hydraulic system 30 times per second to control the elevation of the leveling plate, ensuring that the paving thickness and slope match the set values.
The 3D printing-style pile-free intelligent paving construction follows a rigorous process.
Before operation, the digital intelligent paving equipment is reasonably laid out and debugged according to the type of paver on-site, and the road design model is exported to the paver’s 3D control system to guide intelligent paving and complete elevation verification and other tasks.
During operation, the 3D control system controls the paver’s work based on the three-dimensional model and scans the paved surface, analyzing flatness and thickness in conjunction with pre-paving data. The two sets of scanning data before and after paving are imported into the platform, which calculates the actual paving thickness, generates a color map and cross-section thickness values, and integrates scanning point cloud data for visualization on the Web and APP.
At the construction site, the paver operates autonomously along the “digital trajectory,” eliminating the need for manual hanging lines or setting piles. “In the past, setting piles for several hundred meters could keep several workers busy for a whole day; now, once the equipment is turned on, it can perform precise construction and can work continuously for 24 hours,” said the paver operator.
Unmanned Compaction Cluster: A “Steel Team” with 25% Efficiency Improvement
If 3D paving is “precision embroidery,” then the accompanying unmanned compaction cluster is “cooperative combat.” The project team has achieved unmanned continuous compaction of the water-stabilized layer and asphalt layer during pavement construction, with multiple rollers forming a “steel team” that automatically compacts along preset trajectories, fundamentally solving traditional construction issues such as under-compaction, over-compaction, and excessive speed.
① Beidou Navigation + Intelligent Coordination: Millimeter-Level “Choreography”
The unmanned roller relies on the high-precision Beidou positioning system, achieving a planar positioning accuracy of 2 centimeters, combined with millimeter-wave radar and laser sensors, capable of obtaining precise positioning through the CORS network and sensing obstacles within 10 meters—slowing down by 10 meters and emergency braking by 5 meters in case of anomalies, which is several times faster than human reaction.
“The water-stabilized layer adopts a block-by-block progressive strategy, with clear divisions for initial compaction, re-compaction, and final compaction,” the on-site construction personnel demonstrated the construction plan. During compaction, each roller synchronously compacts within its designated block, and after completion, continues to move forward. Combining millimeter-level data collection for counting, cluster construction is carried out according to the set strategy, ensuring that over-compaction and under-compaction do not occur.
For asphalt surface layer construction, which must follow the principles of close following and slow compaction, a trapezoidal advancement strategy is adopted, where initial compaction equipment must closely follow the paver, creating a trapezoidal area as the paver moves. The unmanned cluster compaction of asphalt must also follow the same advance and retreat strategy, with various types of rollers maintaining a cluster formation to advance and retreat together, creating overlapping compaction areas to ensure timely elimination of each other’s stopping wheel tracks, greatly enhancing construction flatness.
② Three-Level Braking + Intelligent Scheduling: A More Reliable “Safety Officer” than Humans
To ensure the safety of the equipment cluster during construction, the system has set up three levels of safeguards:
Remote emergency stop: Monitoring personnel can stop all equipment with one click on a tablet;
Automatic obstacle avoidance: Radar installed at the front and rear of the vehicle performs real-time scanning, automatically braking when encountering people or obstacles;
Physical emergency stop: Each piece of equipment is equipped with an emergency button on the outside, allowing workers to manually shut down at any time.
Since the system was implemented, the Guangmian Expressway LM4 construction site has achieved “zero safety accidents,” with nighttime construction efficiency improved by 50%—traditional construction often halts at night due to worker fatigue, but unmanned equipment can operate continuously, completing the workload of three days of on-site personnel in 24 hours.
Full Process Intelligent Management: Data-Driven “Transparent Construction Site”
In the intelligent management backend, various construction data is displayed in real-time on the screen: paver speed, roller compaction speed, current road slope, flatness… This reflects the “digital twin” of 3D paving and unmanned cluster compaction technology, and the platform allows for full traceability and control throughout the construction process.
① Full-Cycle Data Closed Loop
On-site paving, compaction, and testing, each link has achieved intelligent control and digitalization:
Quality testing: A 3D scanner can complete a 500-square-meter pavement scan in 10 minutes, generating point cloud data that can accurately calculate thickness and slope, which is 8 times faster than manual testing.
Warning system: When the paving speed is too fast or compaction is abnormal, the platform automatically sends alerts to management personnel, allowing corrections to be made within 30 minutes.
“In the past, to test the compaction of a section of road, multiple core samples had to be taken on-site, and results would take 24 hours; now the system generates real-time compaction color maps, with red areas indicating weak points that can be immediately reinforced,” said the quality inspection head.
② Platform Data Display and Sharing
All data reports on the platform can be shared and viewed through the Web and APP. The platform displays models of different structural layers and combines them with point clouds for quick confirmation of construction progress and quality. Through the platform, design data for the construction area, thickness of each structural layer, material displays, scanning data, and quality analysis reports can all be clearly presented.
Visible Results of Cost Reduction and Efficiency Improvement
Daring to innovate is the driving force behind industry development. The series of intelligent technology applications in the Guangmian Expressway LM4 section has brought significant changes to traditional pavement construction methods. The combination of 3D paving and unmanned compaction, aided by the Beidou navigation system and the 3D laser leveling system, automatically completes the mixing material compaction work, effectively solving the issues of manual errors in hanging lines and balance beams, and avoiding uneven compaction speeds and paths caused by human operation.
Efficiency: The 3D printing-style pile-free intelligent paving eliminates the traditional manual pile setting process, and the efficiency of unmanned cluster compaction is improved by 25%, effectively shortening construction time;
Quality: The standard deviation of pavement flatness has decreased from 1.5 millimeters to 0.8 millimeters, far exceeding regulatory requirements;
Cost: By accurately calculating material usage, waste is reduced, and rework costs are minimized, significantly lowering construction costs.
The Path to Breakthroughs in New Productive Forces Behind Technological Innovation
The intelligent construction practice of the Guangmian Expressway LM4 section is not only an upgrade of equipment but also a revolution in construction concepts. The project team is continuously exploring multiple innovations targeting industry pain points, upgrading the application of new intelligent pavement construction models:
Quadruped robotic dogs replacing manual scanning: Traditional 3D scanning equipment requires two people to carry, while the new quadruped robotic dog 3D scanning process replaces the original manual scanning process, improving scanning efficiency several times. The robotic dog can autonomously navigate obstacles and enter hazardous areas for work, significantly accelerating the entire scanning process. Compared to traditional 3D scanning equipment, it not only completes scanning tasks faster but also shortens construction procedures, improving work efficiency and safety.
“In the past, we relied on experience; now we rely on data. In the past, we competed with manpower; now we compete with computing power. Unmanned equipment cluster construction has become a future-oriented intelligent and refined construction technology,” a project technician remarked.
Empowering “Transportation Power” through Intelligent Construction
As an important section of the Jingkun Expressway, the extensive application of intelligent construction technology in pavement construction by China Railway Fifth Bureau reflects that highway construction in our country is accelerating its transition from “labor-intensive” to “technology-intensive.” When 3D paving with “millimeter precision” meets the “cooperative efficiency” of unmanned compaction clusters, it not only creates a smoother and longer-lasting highway but also cultivates a new productive force centered on technological innovation.
“In the future, we will continue to collaborate with enterprises to optimize these technologies and promote them to more pavement engineering projects, making intelligent construction the norm,” said the project technical leader, looking at the road extending into the distance. This road, infused with wisdom, not only connects the two major regional centers of Guangyuan and Mianyang, shortening the time-space distance of towns along the route but also leads to a new future of a transportation power.
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Information Source | Mechanization Company
Editor | Ruan Jiaying
Organizer | China Railway Fifth Bureau Integrated Media Center
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