Working principle of split set - LinkedIn

Over the past few decades, mining engineering and tunnel construction have faced increasingly complex geological environments. Traditional rock bolt technology often cannot effectively solve the reinforcement problem of surrounding rock, which has prompted engineers to look for new solutions. The split set was born under this background. It quickly gained recognition from engineers with its unique design and excellent performance.

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Split set is a new type anchor of full-length anchoring and active reinforcement of surrounding rock. It has been widely used around the world. It mainly consists of two parts: a high-strength anchor rod and a tray. The surface of the anchor rod has longitudinal slits, which allows it to better adapt to the shape and size of the surrounding rock when installed. When the rock bolt is embedded in the borehole, these gaps can generate friction, thus exerting internal radial pressure on the surrounding rock. In addition, the anchor tray also plays a key role, preventing the surrounding rock from sliding down while providing additional support.

The split set is a high-strength anchor rod with longitudinal slits. When installed in a borehole slightly smaller than the pipe diameter, it can immediately exert radial pressure on the hole wall throughout the entire length and prevent the surrounding rock from sliding over its whole length, together with the supporting force of the anchor tray, which puts the surrounding rock in a state of three-directional stress and realizes the stabilization of the rock stratum. In the case of blasting vibration and surrounding rock movement, there is a significant increase in the later anchoring force. When the surrounding rock is significantly displaced, the rock bolt does not lose its support resistance.

High performance: the friction between the anchor rod and the rock mass is high, and it has high shear and tensile strength; the drilling depth is greater than the depth of the rock bolt, and it can provide timely support in the radial and axial directions. It is not suitable for permanent support in soft rock.

The emergence of split sets has changed people's understanding of geotechnical reinforcement and provided us with new ideas and methods for solving engineering problems with various complex geological conditions. Nowadays, split sets play a significant role in mining projects. We have reason to believe that by further researching and improving the technical parameters and design methods of split sets, we can better play its role in geotechnical engineering and provide a strong guarantee for project construction.

Mpumatech Mining – Split Sets + Washers

Mpumatech, has in a recent drive to expand our product range and after exploring all industry needs for rolled products, have decided to focus on the manufacture of split sets / friction anchors for underground mining and civil engineering projects. Mpumatech have now developed their own split set friction anchor which we manufacture alongside our main product ranges at our facility, conveniently located in Witbank, close to major transport links and hubs in Johannesburg.

The Product

Split sets / friction anchors have been used as a primary roof support in the underground mining environment for many years. The anchor consists of an open seamed high tensile Supraform S420 steel tube with a face plate. One end is tapered for easy insertion into a pre-drilled hole. It is installed by driving the assembly into a marginally smaller hole than the split sets diameter and the welded steel ring then provides the necessary support to hold the washer plate in place. The set then uses friction to anchor itself along the whole length of the bolt by relying on the radial spring force generated through compression of the tube. Split set technology is used worldwide by many mines for an extensive variety of mining applications.

Key Advantages of using Split Sets

• Fast and easy installation
• Full length support
• Effective support at any angle
• Cost effective
• Axial and radial support
• No torqueing or re-torqueing
• No special equipment is required
• Improved rock stability

Changing Ground Conditions

Pull testing on the split set friction anchors proves their superiority in anchoring themselves inside the drilled hole. Once the product has been installed, the spring loading allows the anchor to adapt to minor changes in the ground conditions. This is an important advantage over inelastic bolts that are unable to adapt to changing ground conditions.

Easy Installation

The split set is a popular choice due to its easy installation. Once the hole is drilled, the driver tool drives the anchor into the wall. Installation time is typically less than a minute and there is no waiting time for grout to set, no tightening or torqueing and no ongoing maintenance is needed after installation. This saves time, labour and additional grouting or resin expenses.

Sizes Available

Split set friction anchors are available in 33mm, 39mm, 41mm and 46mm diameters in a variety of lengths to suit the application of the mine. Depending on the strength and corrosion requirements, we offer S420MC Supraform as well as 3CR12 stainless steel. The domed bearing washer plates are available in 125 x 125 x 4mm and 150mm x 150mm x 4mm as well as the Combi Plate 300mm x 270mm x 1.6mm.

Custom specifications are available for large orders.

Packaging

For more Split Sets Underground Mininginformation, please contact us. We will provide professional answers.

Mpumatech wraps and straps all products in high quality packaging with metal straps designed to withstand the rigours of transport by road and sea. This ensures damage is eliminated or kept to an absolute minimum during transport.

Pull Testing

The pull test is a common method to determine the effectiveness of the split sets. From each batch Mpumatech tests a split set in our in-house laboratory to ensure that the product conforms to the required load.  

The first part of the curve signifies the elastic deformation of the steel, the set-up of the test apparatus and the split set. The initial slip load, which is the load at which the split set firsts moves in its hole, is considered to be the split set’s pull-out strength.

The scale of the slip load depends on an array of factors, including the contact area between the Split Set and the rock, the size of the drill hole into which the bolt is installed, properties and type of the rock, the time passed between split set installation, the pull test and the quality of installation.

he pull test should not be regarded as a conclusive measure of the split sets capacity but rather as an index test and one that can give an idea of the expected performance of the split set.

Both in-house and an independent laboratory tensile test are conducted on Mpumatech manufactured split sets to confirm the product conforms to the published specification and  to offer complete transparency to the client. Mpumatech clients can rely upon the standard, consistency and quality of our split set units as supported by these ongoing tests.

Introduction to 3CR12 Stainless Steel Split Sets / Friction Anchors

We have now partnered with Columbus Stainless Steel in South Africa, who are the producers of 3CR12 stainless steel, to manufacture split sets for highly corrosive environments.

A key concern of split sets relates to their useful life span in an underground environment. They are vulnerable to corrosion and can become ineffective after a short period of time, with this in mind we now offer 3CR12 Stainless Steel split sets.

Our 3CR12 Stainless Steel split sets, with similar high tensile properties, is available at a similar price point to the galvanised split sets. Where absolute peace of mind is required, the 3CR12 split set will meet even the most demanding safety standards.

We have conducted salt spray tests to compare the performance between galvanised and stainless steel split sets and the results show the advantage of using 3CR12 material, please click on the following link for the test report:

Salt Spray Test Report

We believe that this is a great alternative solution to galvanised material and could limit the potential for falls of ground where galvanised material fails over time.

Key Advantages of 3CR12 Stainless Steel Split Sets

• Superior corrosion resistance
• Recommended for areas high in acid and salinity
• Galvanised material scratches off when inserting into the hole compromising the steel to the corrosive elements, stainless steel can scratch and remain effective
• Cost effective compared to galvanised split sets
• Can outlast galvanised split sets where they fail over time

To view our online split set brochure, please click on the following link:

Split Set / Friction Anchor Brochure

If you are looking for more details, kindly visit Bolt Pull Test.