Rock movement from mining can cause rock failure, movement due to shear and tensile induced stresses and voids all of which form ideal conditions for anchor bolt corrosion (allowing egress of air, oxygen and any water in the voids caused by the rock dilation).
The immediate roof however may be stable but with time the anchors deteriorate and cause life threatening roof falls.
The overall goal of this thesis is to improve rock related safety underground in coal mines with respect to the effects due to corrosion and optimize support costs over the planned useful life of excavations.
The more specific objectives were to:
• Assess the corrosion potential on the coal mines (based on the water discharge information).
• Quantify the effects of corrosion with time in the 3 different corrosion conditions (the worst, the average and the least corrosive based on the water information results from the mines).
• Recommend Duplex coating rock anchor systems for mines that consider the corrosion potential (not done routinely on US coal mines currently).
• Identify the durability of the anchor materials under realistic ranges of conditions.
• Utilize the potentio-dynamic polarization technique for a quick but accurate measurement of the corrosion potential and the corresponding corrosion current.
• Investigate the corrosion rate of rock anchor steels in acidic and alkaline solutions (to obtain the best and worst case scenarios).