Experimental Investigation Of The Interaction Between Granular Flow And Rigid Barrier

The collapse of granular flow is widely observed in nature and engineering applications.This phenomenon is complex and diverse,which is related to many factors.The gravity-driven granular flows can badly compromise the downstream building structures and transportation facilities.Therefore,it has great significance to study the interaction mechanism between this destructive flow and downstream objects or structures.As a simplified model,the controllable small-scale experiments on granular flow impact can provide an important way to understand this complex dynamic process.Based on the self-designed inclined granular flow platform,this thesis mainly focuses on the relationship of interaction process between the granular flow and the downstream baffle under different conditions,from the two aspects of the evolution of the granular flow state and the characteristics of the dynamic impact force on the baffle.The thesis mainly includes the following aspects:1.Designed an inclined granular flow experimental platform that can accurately control the initial state of the granular flow,including mechanical structure,power system,control system,data acquisition and human-computer interaction interface,etc.;The process measurement method corresponding to the granular flow was established;Designed the image acquisition process and analysis method.In order to process the massive image data in the later period,the contour recognition software based on machine vision method was developed,and the batch data processing program of the granular flow profile was also wrote.2.By setting different types of baffles in the inward granular flow,three series of experimental work were carried out.By controlling the change of the slope angle and the width of the baffle,the granular flow of the bevel under the different conditions was measured.During the flow process,the effects of the above-mentioned parameters on the flow state of oblique granular,the shape of blockage and accumulation during the flow process,and the dynamic characteristics of the granular were systematically analyzed.In the case of partial blockage,three different blocking and stacking morphologies were identified:(a)Form I extending upward,(b)Form II with stable blocking and stacking morphology,and(c)Form III without blocking,and the corresponding stacking and blocking phase diagrams were provided.The value of the characteristic parameter(|w)corresponding to the inclination angle and the width of the baffle with a minimum blocking effect was discussed.For the global blocking situation,two different flow patterns of stable accumulation and flow overflow were observed experimentally.By extracting the instantaneous contours of the granular flow configuration,the granular accumulation morphology and the corresponding evolution characteristics were quantitatively analyzed.3.A series of experimental studies have been performed with the fabricated force-measuring device for research on the impact of inclined granular flow on the inward baffle.The influence of the inclined angle of the inclined surface on the evolution characteristics of the impact force has been measured and analyzed.The blocking and accumulation states of the streams are effectively correlated.On this basis,the influence of the width of the baffle on the evolution characteristics of the impact force was further analyzed,and the maximum value of the impact force,its occurrence time,and the total duration of the impact force are discussed along with the width of the baffle.Finally,a theoretical model of the impact force in the case of a local blockage is established,which can simply predict the evolution characteristics of the impact force over time during the back-propagation in the blocking and accumulation area.In-situ collection of real-world data flowing at different scales in geological hazards lacks operability,and the mass flow that has occurred is difficult to effectively reconstruct due to the many influencing factors,which pose a critical challenge to the understanding of the flow process.This work systematically studies the interaction process between beveled granular flow and the inward baffle,which is based on small-scale granular flow impact experiments.Some interesting macro phenomena and meaningful quantitative results have been reported.This work may reveal the extremely complex interaction mechanism between the granular flow and the protective body,providing an important theoretical basis for the efficiency evaluation of the protective body and engineering optimization design under the influence of multiple variables.