关键词: 轴向应力, 轴向表观应力, 半延性-延性变形, 修正方法

Abstract: In triaxial compression experiments with solid confining pressure medium, especially under high temperature and high confining pressure condition, after reaching the peak strength the macroscopic geometrical deformation of the sample increases obviously with increasing of differential stress. This will lead to a large difference between the observed stress-strain curve and the actual stress-strain relationship. This false appearance will give rise to the unreasonably high residual stress in the sample. To solve this problem, during the semi-ductile and ductile deformation stage of rock sample under the HT-HP condition, a correction of stress-strain curve has been carried out based on the following three assumptions:1) With increasing of differential stress, the originally columnar rock sample deforms into a barrel-shape body;2) The volume of rock sample remains constant;3) During the deformation process, the upside and downside surfaces of the sample keep their original size and shape. That is, the diameter of the upside and downside surfaces of the barrel-shape body should be equal to that of the original sample. The observation after the experiments shows that the rock sample was shortened and bulged in the middle part. This qualitatively indicates that the above assumptions are reasonable to some extent. The examination by using actual experiment data indicates that the correction method proposed here is of practical significance. This method is also applicable to the correction of the stress-strain curve during the semi-ductile or ductile deformation process under axial compression condition.

Key words: Axial stress, Observed axial stress, HT-HP condition, Stress-strain relationship, Semi-ductile and ductile deformation, Correction method