Complex Mechanism Of Granular Materials Under The Condition Of Pipeline Hydraulic Transportation Experimental Study

This thesis took the long distance pipeline transportation and the deep sea mining as a background, basing on the systematical analysis of the previous achievements designed a pipe transport system for experiments concentrated on the velocity, concentration and friction loss under three complex conditions, such as complex space form, complex fluid properties and complex granular composition especially the coarse particles. This research can not only contribute to the development of the technology of long distance pipeline transportation, but also promote to perfect and develop the theory of hydromechanics. The achievements are the following:(1) Based on the previous achievements, we discussed the coarse particles move patterns in the pipes of complex space forms through experiments. As the results of this research, the motion state of the coarse particles in pipes of complex space forms are:1) to horizontal pipes, bed-lead is the major flow,2) to inclined pipes, bed-lead and suspension are the major forms. The suspension of coarse granule requires an extremely high flow velocity that needs high energy consumption. While, rolling flow is an unstable state between movement and static under low velocity that conveying capacity and efficient are low. Therefore, sliding flow is the main form of coarse particles pipe conveyance.(2) We analysed the previous results and proposed that the critical flow velocity of fine particles is homogeneous slurry. The states of flows and the stresses of coarse particles in different pipes were also studied. It can be concluded that the state of particles movement is relative to the grade, the density of solid-liquid and the inclination of pipes. The experiments proved that the critical condition of safe transport of coarse particles in different pipes is the same as the condition of the transfer from rolling to sliding, usually marked by critical velocity, and computational equations of coarse particles in complex space forms were also proposed in this part that can be reference for the pipe transport system parameters design.(3) To consider the point of the fine particles fluid properties, we researched the relationship between shearing rate and shearing stress of the different sizes of fly ash, pulverized coal I (China) under different mass concentrations. It is concluded that, in the study area of our research, the flow curves reveals that all of the three materials have the rheological properties of Binghan body and can be described by the Binghan body rheological equation.(4) We concluded that criticle concentration is the most important criterion to define slurry transfers to paste. When the concentration is lower than this critical concentration, rheological parameter lightly changes, but it will change much sharply when higher than the critical concentration. Thus, Slurry is defined that when the volumetric concentration is lower than the criticle concentration, the yield stress and viscosity coefficient of experimental materials change hardly, and it is more mobilizable but poorer plasticity and when it’s higher, the yield stress and viscosity coefficient of experimental materials change sharply, poorer mobility but more plastic like toothpaste, which is defined as Paste. We analysed the reasons from the perspectives of the physical and chemical features of the superficial of the particles, collision between the particles and the interaction between particle and water.(5) The relationship among the hydraulic gradient, mean velocity, and volumetric concentration and particle size in the horizontal pipes were studied through the self-design pipe transport system. And taking collision into consideration, computational formulations of coarse hydraulic gradient in horizontal pipes were worked out basing on the theory of energy. Meanwhile, we also analysed the change rules of the hydraulic gradient of inclined pipes, and found that the hydraulic gradient increases with the rise of the angle value, or vice versa of the decrease situation, and the values of the hydraulic gradient are symmetrical horizontal lines, then further established an equation for different angles calculation.The errors of the new experimental data and the results from the computational equations of the critical velocity, the hydraulic gradient, and evaluation of the parameters of grain size, mean velocity and volume concentration proposed in this thesis are all lower than20%that in the acceptable range.