To the Calculation of the Trajectory of Hydraulic Fracturing Crack in the Solid Rocks Near In-seam Working


Annotation:

The model of the geomechanics state of hydraulic fracture disk crack in the solid rocks near in-seam working was developed. The peculiarity of this model is the inhomogeneous stress field due to the presence of working. This field plays an important role in the calculation of crack growth trajectory, and under certain conditions significantly changes the stress of the original crack.

The problem on the stress state of the rock mass in the vicinity of the in-seam working is reduced to the second external boundary problem of the theory of elasticity for the integral singular equation. The stresses acting in the boundary zones of the formation are found in the numerical solution of three boundary problems of the limit state theory for a number of areas of the limit zone, and they are approximated by polynomial functions.

During the analysis of the results obtained, the following features in the crack propagation were determined. If the working fluid pressure in the pumping equipment is two times higher than the gravitational pressure in the massif, the hydraulic fracture sharply changes its initial direction propagating to the working circuit. When four times is exceeded, the crack trajectory is straight line and coincides with the direction of the original crack. If the ratio of the working fluid pressure to the gravitational pressure of rocks lies in the interval from three to four, then the crack trajectory has the form of a smooth, flat curve of the line, only at the very beginning slightly changing the direction relative to the initial hydraulic fracturing crack.

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DOI: 10.24000/0409-2961-2019-10-57-62
Year: 2019
Issue num: October
Keywords : rock mass mine working stress intensity factors crack the theory of Griffiths — Irwin hydraulic fracture
Authors:
  • Cherdantsev N.V.
    Dr. Sci. (Eng.), Chief Research Associate, nvch2014@yandex.ru, Federal Research Centre of Coal and Coal Chemistry of SO RAN, Kemerovo, Russian Federation