The S21 Altay-Urumqi Highway Construction Project, Xinjiang’s first desert highway, runs north-south through the Gurbantünggüt Desert, spanning 342.538 km. Designed for a speed of 120 km/h, the route uses a dual four-lane standard from Altay Beitun to Wujiaqu and a dual six-lane standard from Wujiaqu to Urumqi. Upon completion, it will open a direct commercial corridor between northern Xinjiang and Urumqi, reducing regional travel distances, improving transportation conditions, and cutting 260 km from the Urumqi-Altay route by eliminating detours.
As China’s largest fixed and semi-fixed desert, the Gurbantünggüt features sand dunes (10–50 meters high) with a south-high/north-low terrain. Given the region’s harsh environment, construction challenges, and the proven scientific merits of geocell-reinforced aeolian sand (e.g., convenient material sourcing, superior mechanical properties), on-site tests were conducted for the S21 project. The goal: validate geocell-reinforced aeolian sand for upper roadbed filling to achieve local material use, enhance subgrade stability, reduce costs, and enable eco-friendly rapid construction.
Test Section Details
The geocell-reinforced aeolian sand subgrade test section is located in Contract Segment 4 of the S21 Altay-Urumqi Highway Phase I project, spanning K233+660 to K233+840. It uses integral welded geocells (independently developed and produced by Lanzhou Deke Engineering Materials Co., Ltd.) and a 19-meter ultra-wide pre-tensioned laying process. Key objectives include:
– Analyzing dynamic stress attenuation before/after geocell reinforcement
– Mapping stress-strain distribution in geocell-reinforced subgrades
– Validating theoretical models against real-world performance
– Providing engineering evidence for large-scale pre-tensioned laying technology deployment
Geocell Product Specifications
– Type: Welded integral
– Height: 10 cm
– Mesh Size (expanded): 40 cm × 40 cm
– Single Unit Size (expanded): 4.25 m × 18.95 m
– Mechanical Indicators:
– Tensile strength of geocell strips (N/cm)
– Elongation at break (%)
– Node strength (N/cm)
– Weld peel force of U-shaped steel nails (N)
Construction Process
1. Subgrade Preparation:
– Excavate dunes and fill depressions in this semi-embankment/semi-cut section
– Use bulldozers and rollers for dry compaction to meet density requirements
– Verify subgrade elevation with RTK surveying
2. Geocell Laying:
– Test Section: Full Installation (west half of K233+660–K233+840, 180m length); east half as control (no geocells)
– Monitoring Section: K233+750, with sensors (dynamic soil pressure cells, accelerometers, settlement gauges, etc.) buried at different depths to monitor:
– Geocell tensile strain
– Dynamic stress at varying roadbed depths
– Vertical settlement and horizontal soil deformation
– Temperature/humidity changes
3. Pre-Tensioned Laying Technology:
– Track System: 5×4m sliding tension tracks per side, anchored with 40cm-deep bolts
– Tensioning:
– Connect 4 geocell units per Tensioning Unit using specialized connectors
– Attach starting end to 34 anchor piles; secure sides to sliding tracks
– Use a loader to tension geocells to 18–20 kN, ensuring 40cm×40cm mesh integrity
– Backfilling:
– Fill with aeolian sand (10cm above geocell height)
– Compact with rollers after RTK-verified elevation checks
– Remove anchors and advance tracks for subsequent units
Key Outcomes
– Feasibility Verified: The 19m ultra-wide pre-tensioned laying process demonstrated:
– Uniform tensioning (no manual guesswork)
– 40cm×40cm mesh retention under load
– Reduced labor (10+ fewer workers vs. traditional manual tensioning)
– Performance Validation: After 96 hours of loader traffic:
– No voids or dead zones in filled geocells
– Zero strip/node damage; consistent mesh geometry
– Efficiency Gains: Mechanized tensioning eliminates labor-intensive manual stretching, reduces material waste, and aligns with large-scale construction schedules.
