Yoshihiro Kitahara

4. In situ stress measurements in the Japanese islands: Over-coring results from a multi-element gauge used at 23 sites

Abstract The authors have developed a new over-coring stress relief method with a multi-element strain gauge. The new gauge has been used to estimate in situ stress at more than 20 sites for electric power stations in Japan. The results of in situ stress measurements obtained by the method exhibit a general tendency that the maximum compressive principal stress acts horizontally and the horizontal to vertical stress ratio exceeds 1.0. The directions of maximum horizontal compressive in situ stress obtained by the method seem to be consistent with those of the geodetic strains calculated from first order triangulation survey data, and with those estimated from the distribution of tectonic zones which have become active in the Quaternary period. The Japanese islands are located in a tectonically active region, i.e. they are situated near the eastern boundary of the Asian plate towards which both the Philippine Sea plate and the Pacific plate advance. For further detailed discussion a more refined analysis would be required; however, the in situ stress in the Japanese islands is likely to have been significantly affected by these crustal movements.

STUDY ON SEEPAGE FLOW THROUGH ROCK MASS SURROUNDING CAVERNS FOR PETROLEUM STORAGE

ABSTRACT In unlined underground rock caverns, liquid petroleum and petroleum gas can be stored by making use of natural or artificial ground water pressure. In case of applying the unlined underground storage caverns to the cracky rock mass, it seems to be most important that the behaviour of the ground water through the rock mass surrounding the caverns is studied in advance. This study, therefore, discusses the following subjects concerning unlined underground oil storage caverns. 1) The numerical study on the effects of natural ground water pressure on the storage caverns. 2) The numerical study on the effects of artificial ground water pressure on the storage caverns. 3) Model experiment about gas leakage into the crack of rock mass.

SOME CONSIDERATION ON THE NUMERICAL ANALYSIS METHOD FOR ESTIMATING FREEZING BEHAVIOUR OF THE GROUND IN THE NEIGHBORHOOD OF LNG INGROUND TANK

ABSTRACT In this paper, the method of numerical analysis to estimate the frost heaving pressure and the amount of frost heaving caused by the freezing phenomenon of the circumferential ground of LNG inground tank is described. Using the developed program based on the analytical method, in which the non-linear mechanical properties of frozen and unfrozen soils and the characteristics of frost heaving of soil materials are taken into account, the mechanical behaviours of the real LNG inground tank (which has the capacities of 60,000 kl) and the circumferential ground due to the freezing phenomenon of the ground have been taken hold of quantitatively. Furthermore, the comparison of the results due to the theoretical equation proposed by Tkashi to estimate the frost heaving pressure with the results obtained by the numerical analysis are performed and the problems of the case that estimate it in the former are pointed out.