A 39mm split set, also known as a friction bolt, is a widely used rock support element in underground mining, particularly in applications such as ground support in tunnels, mines, and underground chambers. The 39mm refers to the outer diameter of the tube, and a length of 2.4 meters is typical for medium-depth mining operations. These bolts are primarily used for stabilizing rock mass, preventing collapse, and ensuring the safety of underground workers and equipment.

The split set consists of a high-strength steel tube, which is longitudinally slit along its length. The tube is typically 39mm in diameter and is designed to expand when driven into a pre-drilled hole in the rock. This expansion creates a frictional force between the bolt and the rock, which in turn provides support by holding the rock layers together. The length of 2.4 meters is optimal for many mining scenarios, offering a balance between ease of installation and effectiveness in providing the necessary rock reinforcement.

The split set bolt also includes a ring at one end, which serves to hold mesh or plate components against the rock surface. This allows for the attachment of additional surface support, such as mesh or shotcrete, further stabilizing the rock and protecting against loose debris.

The installation of a 39mm split set is straightforward, making it a popular choice in mining operations where speed and efficiency are critical. The process begins with drilling a hole slightly smaller than the diameter of the bolt, typically around 37mm. The split set is then inserted into the hole using a specialized installation tool, usually a jackleg or stoper drill equipped with a split set driver.

As the bolt is driven into the hole, the slit tube expands due to the compression against the rock walls, creating a tight frictional bond. This expansion generates radial pressure that helps to hold the rock in place, reducing the likelihood of rock movement or collapse. Once fully installed, the bolt can support both the rock mass and any additional surface support materials, such as wire mesh or steel plates, which are attached to the ring at the bolt's end.

In mining, the 39mm split set is primarily used for ground support in underground tunnels, stopes, and other excavated areas where rock stability is a concern. The 2.4-meter length makes it suitable for moderate to deep excavations, providing effective reinforcement over a considerable span of rock.

One of the key benefits of using split sets is their ability to conform to the irregularities in the rock surface, providing uniform support even in uneven or fractured rock. This adaptability is crucial in mining environments, where rock conditions can vary significantly from one area to another. Additionally, the frictional nature of the bolt allows it to accommodate small shifts or movements in the rock without losing its effectiveness, providing ongoing support even in dynamic ground conditions.

The 39mm split set offers several advantages in mining applications:

Ease of Installation: The installation process is quick and requires minimal equipment, making it ideal for use in environments where time and efficiency are of the essence.

Cost-Effectiveness: Split sets are relatively inexpensive compared to other ground support systems, such as grouted bolts or cable bolts. Their simplicity also means lower labor costs and quicker installation times.

Adaptability: The bolt’s ability to conform to the rock surface and adjust to small movements makes it highly effective in a range of geological conditions.

Immediate Support: Unlike grouted systems, which require time to cure, split sets provide immediate support upon installation, enhancing safety in active mining operations.

However, there are also considerations to keep in mind:

Load Capacity: While split sets are effective for many applications, they may not provide sufficient support in highly stressed ground conditions where more robust systems, such as cable bolts, are required.

Corrosion: In environments with high humidity or corrosive elements, the steel tube may be prone to corrosion, which can compromise the bolt’s effectiveness over time. Proper coating or use of corrosion-resistant materials can mitigate this issue.

The 39mm split set with a 2.4m length is a versatile and effective ground support tool in underground mining, offering a combination of ease of installation, adaptability, and immediate support. While it may not be suitable for all conditions, its advantages make it a valuable component in ensuring the safety and stability of underground mining operations. Proper selection, installation, and maintenance of these bolts are critical to maximizing their performance and longevity in the challenging environment of a mine.