An Experimental Study on the Mechanical Properties and Expansion Characteristics of a Novel Self-Swelling Cartridge for Rock Breakage

The application of conventional soundless (or silent) chemical demolition agents (SCDAs) is complicated and it is easy for the agents to extrude from boreholes; it is also difficult to use it in wet or up-tilt boreholes, which limits their engineering application. In this paper, the components of conventional SCDAs are optimized and an innovative SCDA cartridge is presented, which is called self-swelling cartridge (SSC). Water absorption, expansion pressure and mechanical property tests of the novel SSC after hydration reaction were carried out to investigate the expansibility and the mechanical properties of the new SSC. The test results indicate that the water absorption rate and the water absorption at full saturation decrease with the increase of the agent packing density. The recommended agent packing density is 1.65 g/cm³, at which the immersion time and the water absorption for full saturation are 9 min and 22%, respectively. The expansion pressure of the SSC is influenced by roll diameter, agent packing density, and insertion gap. The expansion pressure is most sensitive to the insertion gap and least sensitive to the cartridge diameter. An empirical formula relating the expansion pressure and its influencing factors is presented. Both the uniaxial compressive strength and the elastic modulus of the SSC after hydration reaction increase with the increase of reaction time, while the Poisson’s ratio decreases with the increase of reaction time. With the increase of confining pressure, the peak strength increases linearly, which can be described by the Mohr–Coulomb strength criterion. The novel SSC is easy to be used and the SCDA paste is less likely to be extruded from boreholes. It can be applied to fracturing rock masses using boreholes in any inclination, dry or wet. This is important for broadening the application of SCDA.