Experimental study on the pneumatic conveying characteristics of stiff shotcrete materials

The efficient and stable pneumatic conveying of stiff shotcrete materials (SSM) is crucial for underground construction applications such as tunnel support and mining reinforcement. However, the high viscosity, dense particle distribution, and agglomeration tendency of SSM introduce significant challenges to conveying system design and operation. This study establishes a self-developed experimental platform to systematically investigate the pneumatic conveying characteristics of SSM. Experimental analyses focus on the flow regimes, material velocity, pressure drop, and stability under varying pipe diameters and airflow conditions. Results indicate that particle flow behavior is highly position-dependent, with significant transitions between acceleration, stable, and post-elbow stages. Airflow velocity and pipe diameter are identified as critical factors affecting stable conveying velocity and pressure loss, with smaller pipe diameters resulting in higher velocities but increased pressure loss. Furthermore, statistical analyses of pressure signals using probability density functions (PDF) and cumulative distribution functions (CDF) reveal distinct stability characteristics across conveying stages. The findings provide valuable insights into optimizing pneumatic conveying systems for stiff shotcrete materials, enabling enhanced transport efficiency and stability in underground construction scenarios. This study serves as a foundation for future research on the integration of experimental data and numerical simulations to further improve system performance and adaptability.