Numerical simulation analysis of effects of cracks on 4-component borehole observation of stress-strain

The existence of cracks in wall rock of borehole is one of the reasons for the fact that the test values do not meet the self-consistent relationship in borehole observation of stress-strain. However, there are few theoretical researches supporting the fact. The displacements of adjacent components of 45° are calculated using a series of two-dimensional finite element models to qualitatively study the effects of different kinds of cracks on observation. The factors include angles between cracks and the maximum horizontal stresses, ratios of the maximum to the minimum horizontal stresses, distances of cracks and the borehole, length, width and material properties of the cracks. The results show that all the factors have more obvious effects on the borehole stress-strain observation when the crack extension direction is in accordance with the minimum horizontal stress direction or when the ratios of the maximum to the minimum horizontal stresses are larger, the cracks and the borehole are closer, the sizes of cracks are larger, and the differences of the material properties of the cracks and the hole wall are larger.