Abstract
In order to explore the pressure change law of mining wet shotcrete in pipes, the rheological model was built based on rheology principle, and the computational formula of rheological parameters of wet shotcrete was deduced with the linear regression. 100 m full-scale pipeline platform of wet shotcrete was designed and built to study the relationship of pressure and other factors including flow rate, water cement ratio, mix proportion, and pipe bends. Results show: pipe pressure increases with the increase in flow rate and declines with the increase in water-cement ratio, the pressure may fluctuate with a high water cement ratio which can cause cement overhydration and bleeding separation. It will be more beneficial to transport materials if the continuous grading and straight pipe were considered. According to the tests of mix proportion 1:1.5:2.25, the pressure drop is 0.032 MPa·m−1 and the bend pressure drop is 1.3 times higher than in the straight line. We also conclude that solid phase pressure is bigger than liquid phase pressure and they both decline along the pipe based on FLUENT simulation. Finally, the formula of on-way resistance used in mine production was deduced.
Highlights
The application of wet shotcrete technology in mine support is of great importance in some aspects such as decrease of aggregate rebound and dust, as well as improvement of supporting quality
Most research so far has focused on both rheology of fresh concrete and the lubrication layer formed at the interface between the concrete and the wall of the pipe that is the dominant factor to facilitate the pump[1, 3-6]
Since the lubrication layer was first suggested by Alekseev and Weber[16, 17], numerous attempts has been done to estimate lubrication layer thickness based on measuring the velocity profile frontier between concrete bulk and lubrication layer through using various advanced technology[1, 4, 18-21]
Summary
From the point of view of forecasting and controlling pumpability, it is crucial to measure the rheological parameters of wet-mix shotcrete[7-15]. Based on the tribology properties of lubrication layer, the pressure models along pipes of fresh concrete were proposed in Kaplan’ reports[28, 29]. The theoretical model of predicting pumping pressure can be divided into two types: one is for the concrete bulk that does not undergo any shear, the other is the case where both concrete and lubrication layer undergo some shearing in pipes. The formula of on-way resistance used in mine production was proposed to predict the pipe pressure
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