Dynamic modulation of pressure waveforms on slurry penetration in swirl pulsating grouting: performance evaluation and fluid-mechanical mechanisms

Abstract

Although dynamic pressure grouting mitigates particle clogging, the mechanisms of different pressure waveforms on slurry penetration remain elusive. This study proposes a swirl pulsating pressure grouting (SPPG) technique and establishes a three-dimensional transient two-phase flow model coupling the volume of fluid method, Realisable k−ε turbulence model, and Ergun equation. Validated by laboratory experiments, an L25(56) orthogonal array was designed to investigate triangular, sinusoidal, sawtooth, and square waveforms. Tested boundaries included particle sizes of 0.22 to 1.5 mm, mean pressures of 0.08 to 0.14 MPa, and pulsation frequencies of 5 to 20 Hz. A novel Penetration Performance Index (PPI) reveals the triangular waveform exhibits the best comprehensive performance. Fluid-mechanical analyses demonstrate that abrupt waveforms like the sawtooth and square waves induce extreme local pressure gradients reaching 1.48×105 Pa/s, triggering severe kinetic energy dissipation. Conversely, the smooth triangular waveform minimises inertial dissipation with a maximum gradient of only 1.95×103 Pa/s, achieving a 20.21% energy retention advantage over the square waveform. These findings provide actionable guidelines for tailoring pressure waveforms to specific geological conditions.