コアディスキングの表面形状に基づく三次元地圧方向の評価法

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An analysis of tensile principal stress below an HQ core stub was carried out with a finite element method for eleven lengths of core in 25 stress conditions under which core discing is likely to occur. The direction of the semi-axial tensile principal stress, which has an inclination angle relative to the core axis of less than 45°, was analyzed in detail for the central part of the core. Based on the results, a method for estimating three-dimensional directions of in-situ stress from the height at the periphery of the end-surface of a disc was proposed. Main results obtained in this study are summarized as follows:1) The direction of the semi-axial tensile principal stress is fairly uniform in a wide area of the central part of the core and does not depend on the length of core appreciably. Accordingly, the direction of the semi-axial tensile principal stress is considered to govern the geometry of the end-surface of a disc.2) The azimuth of the semi-axial tensile principal stress in the central part of the core approximately coincides with that of the minimum principal stress, while the inclination relative to the core axis (φm) is smaller than that of the minimum principal stress (φ3). A method for estimating φ3 from φm was proposed, which gave an error of less than 25 %.3) When the difference between the normal stresses perpendicular to the core axis (σx-σy) is great, a saddle-shaped disc is formed and the shape becomes more distinct with the increase in the stress difference. However the saddle shape becomes less distinct as the length of core decreases.4) By assuming that the end-surface of a disc is inclined in the direction of the semi-axial tensile principal stress in the central part of the core, a method for estimating three-dimensional directions of in-situ stress from the height at the periphery of the end-surface of a disc was proposed.
社団法人資源・素材学会の論文
2002-11-25

コアディスキングの表面形状に基づく三次元地圧方向の評価法

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