Unraveling the shear behaviors of bonding interface for post-grouted sandstones considering the temperature and confining pressure effects

Abstract

The flow and diffusion of grout within rock fractures, as well as the shear behavior of the grout-rock interface, are notably influenced by grouting conditions, encompassing grouting parameters and geological considerations. Regrettably, owing to constraints imposed by prevailing testing techniques, there exists a scarcity of reports investigating the shear mechanical properties of the grout-rock interface across diverse grouting conditions. This study used a low-field nuclear magnetic resonance (LF-NMR) testing system to conduct permeation grouting tests on fractured sandstones under various grouting conditions, followed by direct shear mechanical tests on the post-grouted samples. The influences of grouting pressure, temperature and confining pressure on the shear mechanical properties of the bonding interface were analyzed. Results showed that higher grouting pressure and temperature conditions led to ductile shear failures due to shear-friction action. An increase in grouting pressure (from 0.5 MPa to 1.3 MPa) increased the peak shear strength and residual shear strength of the post-grouted sample. However, increasing the temperature (from 20 °C to 50 °C) and confining pressure (from 5 MPa to 15 MPa) decreased the peak shear strength and residual shear strength. Meanwhile, with increasing the temperature, both the internal friction angle and cohesion linearly decline, while an increase in confining pressure decreased the internal friction angle but increased cohesion. A shear mechanical model was developed for the bonded interface that accounted for the influences of temperature and confining pressure. Additionally, SEM and XRD examinations yielded valuable insights into the grout filling patterns across various grouting parameters. The findings in this study shed light on the intricacies of grouting performance influenced by grouting conditions, and provide essential guidance for grouting operations in practical engineering.

Keywords

• Grouting
• Fractured sandstone
• LF-NMR
• Shear mechanical property