Friction rock stabilizers (FRS), such as Swellex rock bolts are being considered as reinforcement material for the Yucca Mountain Nuclear Repository. Generally, expanded rock bolts are used for rock support in mining and tunneling applications due to various advantages. Expanded Mn24 rock bolts used for rock reinforcement in underground construction are made of High Strength Low Alloy (HSLA) steel. To our knowledge there are no electrochemical potentiodynamic studies performed on expanded Mn24 in the cold worked condition under certain YM environments for the repository. Corrosion behavior was studied from Potentiodynamic polarization tests performed on expanded Mn24 rock bolt with increasing the concentration of simulated YM water and also as a function of temperature under aerated and de-aerated conditions. Increase in corrosion rates were observed in de-aerated and aerated conditions at room temperature as a function of concentration. Increase in Corrosion rates as function of temperature in YM water chemistry under de-aerated and aerated conditions were observed. Corrosion mechanism of passive layer in anodic region was studied for rock bolt at room temperature in de-aerated condition. Corrosion rates of expanded rock bolt in deaerated are considerably low than the rates in aerated with both increase in temperature and concentration. From the analysis it was found that the uniform and pitting corrosion were the main contributors to the corrosion rate obtained. In this work, we present the corrosion mechanism and corrosion rates of expanded Mn24 rock bolt in different conditions.
Yucca Mountain (YM) is a federal owned land located at 100miles northwest of Las Vegas in the state of Nevada. This uninhabited region has a very dry climate receiving on average of 7.5 inches of precipitation. Underground of YM site was selected for the disposal of commercial spent fuel and high-level radioactive nuclear waste. Further details can be found on the website maintained by DOE. The underground construction of emplacement drifts demands considerable structural support in the form of rock reinforcement. Frictional Rock Stabilizers (FRS), which is widely used in mining industry are ideal for this purpose. Since its introduction in 1970?s, FRS has been widely used in the mining industry to provide roof support for underground construction . FRS is the thin-walled tubular device which exerts force for the entire length of the stabilizer after it is installed inside the rock. Split set and expanded rock bolts are few examples of FRS. This type of stabilizers holds the rock which prevents or minimizes the rock shifts, where as in the case of conventional rock bolts there is a chance of loosen the rock or breaking of rock bolts. The expansion of FRS inside rocks exposes the entire outer surface to the rock. When minerals of the rock combines with water, there is a great potential of rock damage in the form of corrosion. Earlier researchers have studied the corrosion problem of plain steel FRS in the underground mines under different mine water chemistries. Corrosion contribution to the failure of the FRS may be due to many variations in the mine-site conditions. For, example, the water chemistry in the mine is most essential factor for the corrosion. Lian et al. reported the corrosion rates of 1016 low-carbon steels in J-13 water chemistry using electrochemical techniques. Yilmaz et al. reported the corrosion behavior of medium carbon steel (AISI 1040) under simulated YM water, proposed at University of Nevada, Reno (UNR). Since, the water in the mine combined with the rock minerals can produce salts which can contribute the corrosion of rock bolt. J.Ranasooriya studied the Western Australian
