ABSTRACT:

The authors have proposed and discussed temporary storage of low temperature materials such as LNG, LPG and frozen food in openings excavated in rock mountains. In this case, as the rock mass around the openings will receive thermal hysteresis of low temperatures, it is necessary to obtain strength and deformation characteristics of rocks undergoing thermal hysteresis of low temperatures to consider the thermal behavior of rock mass around openings and the stability of openings. In this study, strength and deformation characteristics of some types of rocks were examined after undergoing thermal hysteresis of low temperatures. Then using the results of the tests, thermal behavior of the rock mass around openings was analyzed and discussed. From the results of analysis, it was found that in the case of undergoing thermal hysteresis, length of cracks and freezing zone were almost same as in the case of not undergoing thermal hysteresis.

INTRODUCTION

The authors have proposed and discussed temporary storage of low temperature materials such as LNG, LPG and frozen food in openings excavated in rock mountains. This method has the advantages of efficient utilization of land, energy conservation, large scale storage, preservation of the environment, etc. In this case, the quantity of low temperature materials changes according to their use. For this, as the rock mass around the openings will receive thermal hysteresis of low temperatures, it is necessary to obtain strength and deformation characteristics of rocks undergoing thermal hysteresis of low temperatures to consider the thermal behavior of rock mass around openings and the stability of openings.

In this study, strength and deformation characteristics of some types of rocks were examined after undergoing thermal hysteresis of low temperatures. The effects of amount of thermal hysteresis, atmosphere temperature, porosity, etc. on strength and deformation characteristics of rocks were discussed.

In this study, it is supposed that an opening is excavated in a granite rock mountain to a depth of 100m beneath the ground surface with a diameter of 10m. LNG at -162øC was stored within and rock mass around the openings was received the effects of thermal hysteresis of low temperatures as the quantity of LNG changes continually.

In this case, using the results of the tests, temperature and stress distribution around openings were analyzed by Finite Divided Element Method (FDEM) (Inada & Shigenobu 1983) and Crack Analysis Method (CAM) (lnada & Taniguchi 1987). Then the effect of thermal hysteresis of low temperatures on thermal behavior of the rock mass around openings are discussed.

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