Experimental study on the flow characteristics of horizontal pneumatic conveying of stiff shotcrete

Abstract

The gas-solid two-phase flow of stiff shotcrete in horizontal pneumatic conveying was experimentally studied to reveal the flow characteristics of stiff shotcrete in a horizontal pipeline. Pressure data and particle flow characteristics were measured by pressure transmitter and high-speed camera, respectively. The unit pressure drop and particle flow characteristics in the steady state zone of stiff shotcrete under different air volumes of flow, water cement ratio, and pipe diameter were systematically studied. The results show that the unit pressure drop increases with the increase of the water-cement ratio; the pressure drop per unit length in the steady state zone decreases first and then increases with the growth of air volume of flow, and there is the most economical air volume of flow. Through image analysis, it is found that with the increased air volume of flow, the stiff shotcrete particles gradually transform from stratified flow to suspended flow in the pipeline. In addition, the stability of stiff shotcrete during pneumatic conveying is studied by analyzing the variation coefficient of pressure. The stability increases with the decrease of the pressure variation coefficient. This study further reveals the pneumatic conveying mechanism of stiff shotcrete, which provides essential guidance for designing a pneumatic conveying system and the experimental basis of stiff shotcrete.