PSI - Issue 32

A.K. Fedoseev et al. / Procedia Structural Integrity 32 (2021) 202–208 A. K. Fedoseev/ StructuralIntegrity Procedia 00 (2021) 000 – 000

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problem arises though when the strain rate of loadbearing elements (pillars) is higher than the backfilling rate. In that case additional measures for mine preservation are necessary. One of the possible methods to prevent water inflow into mine openings is to make antifiltration screen between the failure zone in waterproof stratum and aquifers by the means of grout injection. For some potash deposits the only way to do this is to drill a borehole from surface to upper border of waterproof stratum and pump grouting material through it under high pressure. Obviously, the additional impact on the previously disturbed salt layers is bound to influence their stress-strain state and at the worst even to lead to further complication of already dangerous situation. Hence the necessity of preliminary geomechanical research on estimation of additional impact of pressure from grout injection on stability of already From the viewpoint of continuum mechanics problem statement injecting of grouting material can be considered as applying additional pressure in rock. When pumping through a single borehole situated over the center of fault area the pressure distribution is applied to the upper border of WPS with its maximum at the borehole exit (Fig.1a). Analytical calculations of pressure distribution in the vicinity of pumping borehole 1 were based on well-known approaches of underground hydromechanics (Basniev K.S. et all, 2006). To determine propagation radius of grouting material the following assumptions were made: constant pressure is maintained at the injection borehole; constant permeability and capacitive properties in the area of grouting; the displacement front movement occurs without interfusion; different viscosities of displacing and displaced solutions; there is no residual water saturation in the zone of displacing solution propagation. The influence of grouting material density on its propagation radius wasn’t taken into account due to short duration of pumping process (within an hour). weakened waterproof stratum. 2. General problem statement

Fig.1. Calculation schemes for various pumping scenarios

1 Calculations were executed by Ph.D. of Geologo-Mineralogical Sciences A.A. Potapov