14 factors associated with the installation of a rock-bolt

14 FACTORS ASSOCIATED WITH THE INSTALLATION OF A ROCK-BOLTThe quality of roof support achieved with rock bolts depends more on the quality of installation, than on the theoretical strength of the bolts.

The cost of installing rock bolts is high. How high depends on many things: the method of mining, the method of installing bolts, the accessories used with the bolts, how many bolts must be installed to guarantee adequate support of the rock and, most of all, how well they are installed.

The factors that affect the price of installation are as follows:

  1. The cost of the fixture or rock bolt.
  2. Other installation materials such as expander shell, cement, resin or silicate cartridge.
  3. As rock bolts are seldom installed without accessories, we have the cost of such items as washers, bearing plates, strapping, wire mesh and wooden blocks.
  4. Some of these materials as well as some types of rock bolts are more susceptible to loss and damage than others, and this must be taken into consideration.
  5. The costs of transportation to the mine as well as internal transport.
  6. Installation costs include the various pieces of equipment used to install bolts and the replacement and repair costs on this equipment. The main methods of installation are manual, using a hydraulic device or using a pneumatic device. Also included in the installation cost is the labour.
  7. The cost of drilling a hole; the length and diameter may vary for different types of bolts.
  8. The most important cost is the cost of unsuccessful installation. This is also the most difficult to estimate. But it is this that determines the number of bolts required.
  9. The regulations often require that representative samples of the bolts installed be pulled and torque tested.
  10. Servicing of rock bolts is also costly. Mechanical bolts loose their tension and must be retorqued.
  11. If screening is used and new holes are required to overlap the screen, this adds greatly to the bolting cost.
  12. Sometimes screening is carried out throughout a tunnel while it is required in some portions only. The reason for this is the high cost of coming back to drill and install the screen. Some bolt types can be fitted with screen after installation and some cannot.
  13. If insufficient bolts or poor installations result in rock falls that disrupt production and rebolting is required, the cost is greatly increased.
  14. The speed of the installation of bolts increases production and affects the costs.

 

No matter the type of accessories used, a proper installation is crucial. The proper use of IPKON’s silicate capsules in conjunction with rock bolts can greatly minimize the risk of faulty installation and can reduce the global cost of rock support.

2 thoughts on “14 factors associated with the installation of a rock-bolt

  1. I agree with your opening statement and in fact some time ago PHQ developed a list of twenty items associated with the costs of ground control in hazardous underground areas that contains most of your comments. I modified our list using some of your wording and put the items in almost the same order. Experts in ground control could possibly add more to this list of costs.

    The factors that affect the costs of ground control in hazardous areas with rock bolts are as follows:
    1) Landed cost of purchasing rock bolts including washers and/or tension plates.
    2) Landed cost of installation materials such as expander shells, cement, resin, or silicate cartridges.
    3) Landed cost of strapping, wire mesh, strapping or other support materials installed with the bolts.
    4) The cost of purchasing, storage and warehouse handling of inventory of all these related products.
    5) The cost of transporting the bolts, installation materials, and mesh from storage to the work site.
    6) Rock bolting materials are highly susceptible to loss (left lying in fill stopes) and damage (run over).
    7) Installation costs include capital cost of dedicated equipment used to install bolts as well as maintenance service and repair parts costs to keep the equipment running.
    8) The single highest cost of installing bolts is usually the cost of labour to drill holes and install bolts.
    9) The cost of dedicated engineering and technical personnel to support ground control requirements.
    10) Speed of installation of efficient bolts and screen is of the essence to minimize labour costs.
    11) The cost of bits and steel to drill holes (length and diameter vary for different types of bolts).
    12) The cost of energy supplied to the pneumatic or hydraulic equipment used to install bolts.
    13) The cost of lost production time of mine ore spent installing required bolts and mesh.
    14) The cost of recovery of blasted bolts and mesh from production ore handling (minimal).
    15) Extra costs are incurred in unsuccessful installation – re-drilling and installing additional bolts.
    16) Extra costs are incurred for extra bolts if screen needs to be overlapped or spacing is not followed.
    17) Extra costs are incurred if bolts and screen are installed in areas where not required.
    18) Extra costs are incurred if samples of installed bolts are rendered useless in destructive testing.
    19) Extra costs are incurred if bolts need to be inspected and re-torqued at later dates.
    20) Extra costs are incurred if inspection requires re-bolting due to insufficient bolts or poor installation.

  2. The 15th and possibly the most important aspect of rock-bolt installation is safety. No matter how good the materials utilized, the method of installation, be it manual or mechanized, and how it is monitored is vital. One of the safest and most versatile rock bolters I have come across, is the Rockman Bolter being manufactured by Nkangala Mining Equipment, Middelburg RSA.

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