In the demanding environments of underground mining and tunneling, ground support systems must provide immediate load-bearing capacity, adapt to unpredictable rock movement, and ensure long-term safety. SupAnchor, a leading Chinese manufacturer of self drilling anchor systems and geotechnical reinforcement systems, has introduced the SupHulk® friction rock bolt system to meet these challenges in projects across Europe, North America, and beyond. The SupHulk Premium (PM) line is a high-yield, high-deformability tunneling bolt that is being deployed in applications ranging from deep mine roof support to large-diameter tunnel excavations.
Friction bolts, also known as Swellex-type bolts, operate on a simple mechanical principle: a sealed steel tube is inserted into a borehole and then inflated with high-pressure water. As the tube expands against the borehole wall, it creates friction and interlocking along the entire length, providing full-column support. This mechanism allows the SupHulk bolt to bear full load directly after installation, absorb rock movements immediately, and distribute carrying forces evenly—without the curing time required for grouted bolts. This makes it particularly valuable in projects where rapid advance rates and immediate safety are paramount.
The SupHulk PM series is available in three models—PM12, PM16, and PM24—each designed for specific load requirements and ground conditions. The minimum breaking loads are 110 kN, 160 kN, and 240 kN respectively, while minimum yield loads are 100 kN, 130 kN, and 200 kN. All models achieve a minimum elongation of 10% (A100mm), a critical property that allows the bolt to accommodate significant shear movements in medium to soft rocks without failure. This high elongation capacity reduces the risk of sudden bolt rupture in squeezing ground, a common challenge in deep mining and tunneling.
Installation parameters are equally important. PM12 and PM24 require an inflation water pressure of 300 bar, while PM16 requires 240 bar. The recommended borehole diameters are 32–39 mm for PM12 and 43–52 mm for PM16 and PM24. The original tube diameters are 41 mm for PM12 and 54 mm for the larger models, ensuring a controlled expansion ratio that maximizes friction. A 50 cm long inflated bolt section can generate 100 kN of friction, providing robust anchorage even in weak or fractured strata. The steel profile can withstand shear movements without failure, and the bolt can adapt to borehole irregularities, bridging gaps in the rock.
The table below summarizes key specifications for the SupHulk PM series:
| Parameter | PM12 | PM16 | PM24 |
|---|---|---|---|
| Minimum breaking load (kN) | 110 | 160 | 240 |
| Minimum yield load (kN) | 100 | 130 | 200 |
| Minimum elongation A100mm (%) | 10 | 10 | 10 |
| Inflation water pressure (bar) | 300 | 240 | 300 |
| Recommended hole diameter (mm) | 32–39 | 43–52 | 43–52 |
| Profile diameter (mm) | 27 | 36 | 36 |
| Tube thickness (mm) | 2 | 2 | 3 |
| Original tube diameter (mm) | 41 | 54 | 54 |
| Upper bushing diameter (mm) | 28 | 38 | 38 |
| Bushing head diameter (mm) | 30/36 | 41/48 | 41/48 |
In addition to these mechanical properties, the SupHulk PM series is available in lengths from 1.2 to 6 meters, with corresponding weights that facilitate logistics and handling. For example, a 3.0-meter PM24 bolt weighs 10.6 kg, while the same length PM12 weighs 6.0 kg. This predictable weight distribution helps contractors plan transport and installation equipment efficiently.
SupHulk rock bolts are highly versatile and can be used in a wide range of tunneling and mining systems. In tunneling, they are typically employed as pattern bolts to support excavations, with the bolting pattern determined by the size of the excavation and the properties of the rock mass. In mining, common applications such as roof bolting and hanging wall bolting have adopted SupHulk as a rapid, safe, and high-performance device. The immediate load-bearing capability reduces downtime and enhances worker safety, especially in high-stress environments.
Key operational features of the SupHulk system include:
The simplicity of the installation process is another major advantage. The operator drills a hole, inserts the bolt, and inflates it to a pre-determined pressure using a specially designed inflation system. The pump automatically stops when it reaches the recommended inflation pressure, ensuring consistent installation quality. Additionally, SupHulk bolts can be easily pull-tested at any time to verify performance, providing assurance for project engineers.
The global push for infrastructure development—from metro systems in Europe to mineral extraction in North America and Australia—demands ground support solutions that are both reliable and cost-effective. Friction bolts like the SupHulk PM series address this need by combining high load capacity, rapid installation, and long-term durability. Their ability to provide immediate full-column support reduces the need for secondary reinforcement, lowering overall project costs and shortening construction schedules.
In mining, where ground conditions can change rapidly, the SupHulk system’s high elongation and friction anchorage help prevent roof falls and sidewall collapses, protecting both personnel and equipment. In tunneling, the bolt’s adaptability to borehole irregularities and its gap-bridging capability make it suitable for challenging geological formations, including soft ground and fault zones.
SupAnchor’s commitment to innovation is evident in the SupHulk design. As a leading soil nail system manufacturer and ground anchor bolt factory, SupAnchor produces a full range of self drilling anchor systems, hollow bar anchors, and drill-and-grout bolts. The company’s R&D team continuously refines product specifications to meet international standards, and its manufacturing processes follow ISO quality management principles. With installations in major infrastructure projects across more than 50 countries, SupAnchor has established itself as a trusted partner for geotechnical reinforcement.
The SupHulk friction rock bolt system embodies the brand’s core values of professionalism, innovation, and collaboration. By delivering reliable, high-performance ground support, SupAnchor helps engineers and contractors overcome complex geotechnical challenges, ensuring the safety and success of critical projects worldwide.
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