| บทคัดย่อ(English) |
The objective of this research is to evaluate the mechanical performance of the rock salt formations in the Northeast of Thailand for use in the compressed-air energy storage. The task involves literature review of the relevant research topics, the characterization tests, the fracture healing and the cyclic loading experiments on rock salt from Sakon Nakhon basin, and computer modeling of the cavern for this technology. The test results indicate that the compressive and tensile strengths of the rock salt specimens obtained from Sakon Nakhon basin used in this research are relatively high as compared to those from various sources. The healing test results indicate that under the confining pressure of 1,000 psi for about 100 hours, salt fractures can be healed and can gain the tensile strength up to 90% of the intact strength. The cyclic loading results indicate that the fatigue strength (S) decreases with the increase of loading cycle (N): S = 33.6 N(-0.08). The elastic modulus decreases as the number of cycle increases, and ranging between 20 and 30 GPa. Review of the drill-hole data obtained by the Department of Mineral Resources indicates that only few areas in Northeastern Thailand pose appropriate depth and thickness of the salt formations that are suitable for the compressed-air storage caverns. In this study the depth and thickness of salt formation at Borabu District have been selected for use as an example area for computer modeling. The simulation results show that spherical cavern has the smallest closure of the cavern and the narrowest plastic zone around the cavern boundary than those of the elliptical and cylindrical caverns. For the cavern at 600 m depth, the maximum and minimum safe storage pressures should be about 90% and 30% of the in-situ stress at the cavern top. The withdrawal and injection rates for the daily cycle should be about 96 psi/hour. This will result in a long-term mechanical stability of the surrounding salt. The maximum surface subsidence at 20 years after operation would be about 20 cm. |
