MEE10001Materials and Processes Assignment 1 Rock Bolts23/05/2014Lucas Morgan andWill Huson 76627937694210Rock Bolts:A rock bolt is used predominantly in mining to reinforce rock faces.This is accomplished by inserting a rock bolt into the rock face and tightening a plate on the bolt that compress the rock face; this stabilizes the compressed sections of rock so the face doesnt fall apart.See Diagram: 1.1 *Obtained from reference 1.

Types of rock bolt:There are a number of different types of rock bolt in use; however all need to be fixed into the drilled hole in the rock face to function. There are three main styles of rock bolt that accomplish this with different strengths and weaknesses.Expansion shell BoltsBolt is inserted into undersized hole by force and remains there through friction with the hole.Quick to install, but unsafe to use on unstable rock face. Moderate strength, long lifetime.Swellex -dowel Bolts Bolt is inserted into oversized hole, and then the bolt is filled with concrete to occupy the bolt-hole.Cheap and quick to install, reliable, and safe to use in most situations, however corrosion is a concern as hollow bolt is in contact with rock. High strength, long lifetime.Cable BoltsCable is inserted into hole, which is then filled with concrete and capped.Very cheap and easy to tension and install, but difficulties arise with the concrete installation around the cable. Low strength, reasonable lifetime.

As injection bolts have a high strength, long lifetime, and are reliable while remaining cheap we will look at the material selection for this style of bolt.Performance requirements:Tensile Strength-So bolts can withstand tensioning to support the rock face.Low Mod. Of Elasticity-Required so bolts can be expanded by concrete injection when installed.Moderate % elongation-Essential so when bolts stretch when under tension they do not fail.Weight; lower is better-Welcome when installing materials on a large scale or in delicate rock faces.Corrosion resistance -Required for lifetime durability as the material will contact its environment. 3 materials come to mind in regard to these criteria; Materials/Property*Reference 2.Tensile StrengthModulus of Elasticity% Elongation at breakDensityCorrosion Resistance

AZ31B Manganese Steel Alloy290 MPa45 GPa15%1.8 g/cm3Poor

Al2024 Aluminium Alloy485 MPa72 GPa18%2.8 g/cm3Good

Ti-5Al-2.5Sn Titanium Alloy760 MPa110 GPa16%4.5 g/cm3Very Good

Materials costs and availability:AZ31B Manganese Steel Alloy: Widely available, cost of approx. 2.5-3.5 thousand USD per tonAL2024 Aluminium alloy: Widely available, cost of approx. 3.5-4 thousand USD per tonTi-5Al-2.5Sn Titanium alloy: Not so common, cost of approx.20-45 thousand USD per tonProcessing and Environment:To obtain the Aluminium alloy, heat treatment followed by cold working is required, which involves some heavily energy dependent processes, which means a large environmental footprint.For the Titanium alloy heat treatment and smelting contribute to a relatively higher environmental footprint compared to the other two materials.Finally in regard to the Manganese Alloy, it involves less energy in its production than the other two materials, and so has the smallest environmental impact of the three materials.Conclusion:We recommend using Al2024 aluminium alloy, which has been solution heat treated then cold worked and finally aged at room temperature, to meet the performance requirements of Swellex-dowel rock bolts.This material satisfies the design requirements of Swellex-dowel bolts well without costing too much in comparison with the other two materials discussed. In addition it has a relatively low weight while having good corrosion resistance, tensile strength and modulus of elasticity. Despite the Titanium alloy meeting all of the requirements better than the other materials its lower availability and cost of up to 10 times as much was a strong limiting factor in its use on a large industrial scale.

References:1. ASM Material Data Sheet. 2014. ASM Material Data Sheet. [ONLINE] Available at: http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MA2024T4. [Accessed 23 May 2014].2. 14-Rock Bolts and Cables [Article accessed ONLINE] Available at: http://www.rocscience.com/hoek/corner/14_Rockbolts_and_cables.pdf. [Accessed 23 May 2014].3.William D. Callister Jr., David G. Rethwisch, 2014, Materials Science and Engineering, An introduction 9th edition.