k. ghoshtasbi

Compressed air storage is one of the methods of energy storage. One of the most important parts of a compressed air storage system is the storage cavern. In this study, the behaviour and the long-term stability of the salt cavern as a storage site for compressed air were investigated. Due to the construction and operation of the salt cavern, the in-situ stress conditions around the cavern will change. The difference between induce stress and pressure of compressed air will cause the cavern to converge and damage around it. In this study, the salt rocks from one of the regions of Iran were used to test creep. To investigate the creep behavior of salt rock, creep test was performed in three stress levels in a stepwise manner. Lubby2 model parameters were calculated. Then, using LOCAS finite element software, the compressed air storage cavern was simulated and its behavior and stability were investigated. The results of these experiments and modelling have shown that with increasing stress in each stage, the slope of the secondary part of the creep increases. Therefore, it can be concluded that with increasing stress, the Maxwell viscosity coefficient decreases. In addition, the amount of movement in the lower half of the cavern was more than the upper half of it. Value of the cavern safety factor according to the Devries dilation criterion also decreased with increasing depth and the probability of dilation in the cavern wall increased.

With regard to the types of risks existing in tunnels, geotechnical risks play an important role in the selection of tunneling method and machine types. Also, in order to prevent some geological and geotechnical hazards during tunneling, selecting the most appropriate tunneling machine is very important. In this research study the main geotechnical hazards of tunneling by Roadheader with their common mitigation measures were specified. At present, three Roadheaders are excavating the three drifts of the Tabas coal mine in Iran. Hence, the above drifts were used in this research study. The risk assessment matrix method in these tunnels showed that there is a lower risk of tunneling by Roadheader than utilizing the drilling and blasting method. The determined geotechnical risk assessment also showed that the transverse cutter head is more suitable in comparison to a longitudinal cutter head for such tunnels. Then by using an instantaneous cutting rate model, the cutter head power of the Roadheader was determined. According to the model, a light weight Roadheader with a cutter head power of about 80-110 Kw and 40 ton weight are suitable. Finally, the four types of manufactured Roadheaders which their specifications were similar to the determined ones were selected.