An ambitious highway expansion through geologically challenging terrain has turned to SupAnchor's proven self drilling anchor system to safeguard long-term slope stability and tunnel portal integrity. The Longmenshan Expressway Expansion Project, a key artery in western China, encountered highly fractured rock and loose overburden that rendered conventional anchoring methods unreliable. By deploying SupAnchor's integrated drill-and-grout bolt technology, contractors achieved rapid installation with minimal ground disturbance, setting a benchmark for modern geotechnical reinforcement systems in transportation infrastructure.
The project, which adds 32 kilometers of new tunnel and bridge sections, faced slope instability at multiple tunnel portals and deep cuts. Preliminary borehole investigations revealed a chaotic mix of weathered phyllite, clay gouge, and groundwater ingress – conditions notorious for hole collapse and grout loss during drilling. Traditional casing advancement methods were too slow and expensive, while standard soil nails lacked the required tensile capacity. The engineering team specified a self drilling anchor bolt solution that could drill, grout, and anchor in a single pass, eliminating the need for temporary casings and preventing borehole collapse.
SupAnchor’s self drilling anchor bolts, also referred to as hollow bar anchors, provided the versatility needed to handle variable ground. Using a sacrificial drill bit attached to the hollow steel bar, crews advanced anchors to design depths of 12 to 18 meters while simultaneously injecting cement grout under pressure. This drill-and-grout bolt method formed a grout-soil bond that exceeded design expectations, even in water-saturated zones.
“The ground conditions changed every few meters,” noted site supervisor Li Wei. “With the hollow bar anchor, we avoided having to switch between drilling and grouting phases. The continuous installation kept our crews safe and accelerated the critical path schedule.”
Over 6,800 anchors were installed across five cut slopes, with the largest slope rising 78 meters and reinforced by four tiers of anchors. The ground stabilization anchor system employed R32 to R51 hollow bars, with lengths tailored to intersect potential failure surfaces. Real-time grout pressure monitoring ensured consistent grout-filled boreholes, while double corrosion protection was applied to permanent anchors in aggressive soil environments.
The self drilling anchor for retaining walls and slope stabilization delivered performance figures that matched the rigorous demands of the site. Key specifications of the SupAnchor SDA bolt factory direct supply model used on this project are summarized in the table below.
| Parameter | Value/Range | Application Benefit |
|---|---|---|
| Bar Diameter | R32, R38, R51 | Adapts to different load requirements and ground conditions |
| Yield Strength | 500 – 670 MPa | High tensile strength for surcharge and dynamic loads |
| Ultimate Tensile Strength | 600 – 800 MPa | Safety factor compliance for permanent works |
| Bond Stress (grout-soil) | > 1.5 MPa (tested on site) | Reliable load transfer in fractured rock |
| Corrosion Protection | Hot-dip galvanizing (80 μm) or Double Corrosion Protection (DCP) | Ensures 100-year design life for critical infrastructure |
| Drill Bit Type | Tungsten carbide button or cross bit | Effective through hard inclusions and mixed face conditions |
The high‑strength hollow bar anchors acted as both a drilling rod and a full‑scale tension element, reducing the number of components and potential weak points. SupAnchor’s self drilling bolt for civil engineering applications also incorporated a left‑hand thread on the coupling, enabling continuous extension without losing the ability to rotate right‑hand during drilling—a feature that proved vital when depths exceeded 20 m.
The twin challenges of water‑bearing loosened ground and steep slope faces demanded an anchor bolt system for geotechnical engineering that could maintain borehole stability from start to finish. By using a ground stabilization anchor system that pumped grout through the hollow core while drilling, the SupAnchor method created a grout jacket around the bar that filled voids and sealed off water pathways. This not only increased the pull‑out capacity but also reduced the risk of developing progressive slope failures during excavation.
In sections where the rock mass was highly blocky, the self drilling anchor system functioned essentially as a micropile hollow bar anchor, reinforcing the ground mass and improving the global factor of safety. Load tests confirmed that the bonded lengths provided by the micropile hollow bar anchor technique met the 1.75 safety factor specified for permanent works, even after severe rainy seasons.
The deployment of such an advanced geotechnical reinforcement system on a critical highway project underscores a global shift towards more resilient and time‑efficient ground support methods. As governments worldwide invest in modernizing transportation networks—from European trans‑Alpine tunnels to North American mountain passes—demand is growing for anchor solutions that can cope with unpredictable geology without compromising safety or schedule.
The soil nail system manufacturer segment, traditionally associated with cut slopes, is expanding into hybrid techniques that combine soil nailing with high‑capacity self drilling anchors. SupAnchor’s approach blurs the line between a conventional soil nail and a fully grouted tension anchor, offering designers a scalable ground anchor bolt factory solution that adapts from temporary excavation support to permanent retaining structures. The self drilling anchor for retaining walls at the Longmenshan site exemplifies how one single system can handle both active and passive reinforcement, enabling value engineering without compromising performance.
Similarly, the rock bolt for underground mining sector has long relied on quick‑installation bolts in demanding conditions. The principles applied here—self‑drilling, simultaneous grouting, and immediate pre‑tensioning—are now crossing over into civil infrastructure, where downtime and retrofitting costs are intolerable.
As a recognized rock bolt for underground mining and ground anchor bolt factory, SupAnchor has built a reputation for manufacturing excellence and continuous product development. The company holds ISO 9001, ISO 14001, and ISO 45001 certifications, and its self drilling anchor systems have been validated on over 200 major projects across more than 30 countries. From European rail tunnels to Southeast Asian hydropower caverns, the SDA bolt factory direct supply model ensures consistent quality and competitive lead times, while dedicated engineering support helps owners and contractors optimize anchor designs.
“Every hollow bar anchor we deliver is a critical safety element,” said Zhang Ming, SupAnchor Technical Director. “We don’t just supply steel; we provide a complete geotechnical reinforcement system backed by rigorous testing and on‑site support.”
The self drilling anchor bolt used on this project exemplifies SupAnchor’s design philosophy: integrate multiple functions into a single, robust component to save time and reduce risk. The use of high‑quality alloy steel, precision threading, and advanced corrosion protection has made SupAnchor a preferred partner for contractors facing the most demanding ground conditions.
With the slope stabilization works now substantially complete, the Longmenshan Expressway expansion is on track for its scheduled opening, and the anchored slopes have shown negligible displacement during subsequent heavy rainfall events. The successful application of the ground stabilization anchor system has already influenced design approaches for two other mountain expressways in the region, where self drilling anchor for retaining walls will be used to replace more expensive piling methods.
As infrastructure spending continues to climb, and projects push into ever more marginal ground, the role of the self drilling bolt for civil engineering will only become more central. SupAnchor’s continued investment in R&D, such as developing larger‑diameter hollow bar anchor for heavy‑load micropile applications, positions it well to serve the next generation of geotechnical challenges.
Press Contact: SupAnchor Communication Department | [email protected] | www.supanchor.com
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