Experimental Investigation on the Grouting Diffusion Characteristics and Relative Filling Degree of Chemical Slurry in Fractured Porous Sandstone

In this study, several chemical grouting tests of fractured porous sandstone were performed based on the low-field nuclear magnetic resonance (NMR) technology, and the nuclear magnetic signal characteristics (NMR T2) of slurry were tracked and tested in real-time. The variations in the injected slurry volume, effective grouting time and slurry permeability with different confining pressures, injection pressures and fracture inclination angles were quantitatively analysed. Besides, the relative filling degree (RFD) was proposed to comprehensively investigate the diffusion processes under different grouting conditions. The results indicate that both the high confining pressure (e.g., 20 MPa) and large fracture inclination angle (e.g., 27°) induce the decrease in injected slurry volume by the rate of 16.7 and 44%, while the effects induced by injection pressure is not obvious. The permeability of slurry in fractured porous sandstone linearly decrease as the confining pressure and fracture inclination angle increase, coinciding with the decrease amplitude of 67.1 and 44%, respectively. The slurry diffusion pattern in fractured porous sandstone is strongly dependent on the confining pressure, injection pressure and fracture inclination angle. Both the relative filling degrees of rock pores and fractures decrease with increasing confining pressure and fracture inclination angle.