Research On Rebound Rate Of Wet Shotcrete Based On Discrete Element Method

Sprayed concrete is increasingly used in the field of support,compared with dry spraying,wet sprayed concrete has a low rebound rate,less dust production,and good quality of concrete spraying surface,which has become a hot spot for people to study.With the development of technology,people have higher requirements for wet spraying support,how to further reduce the rebound rate and improve the spraying efficiency is an important factor in evaluating the good and bad of concrete spraying support.The paper studies the relationship between particle radius,injection distance,nozzle shrinkage angle and injection rebound rate in the process of concrete injection,which has important theoretical significance and engineering practice value.At present,most of the research around concrete is to study its fluidity,pumpability,etc.,and there is less research on concrete in the spraying process,however,to study concrete in the spraying process,we have to start from the structure of the nozzle.In this paper,the relationship between the shrinkage angle of wet shotcrete nozzles,spraying distance and particle size is investigated by numerical simulation plus experimental studies,with the aim of finding the optimal rebound rate for a given particle range and the range or specific values of the shrinkage angle and spraying distance corresponding to the optimal rebound rate.The research in this paper consists of the following aspects.(1)The spraying model of concrete was established using the discrete element software PFC3D.First,the nozzle convergence and shrinkage sections and the sprayed surface were modeled,the particle models representing the aggregate and slurry were established and assigned to the models,and then the microscopic parameters of the models were calibrated by field shotcrete experiments.(2)The influence of key parameters on the rebound rate of shotcrete was analyzed.By establishing a discrete element model,the relationships between the shotcrete rebound rate and the initial velocity at different particle sizes were explored by combining the derived microscopic contact parameters with the shotcrete rebound rate,and the data from the simulations were processed using Origin drawing software to derive the influence of some parameters on the rebound rate.(3)An optimal algorithm was derived.By comparing with the simulation results of discrete element software,the feasibility of the optimal algorithm was verified,and a lot of time was saved for the numerical simulation experiment.(4)The relationship between injection distance,shrinkage angle and particle size and rebound rate is analyzed.The optimal algorithm model derived from the machine learning algorithm was used to calculate the data several times,and a large amount of data was obtained.The data was then imported into Origin,and the 3D surface plot and contour color filled plot between the parameters and the rebound rate were plotted,from which the values of injection distance and shrinkage angle could be derived for different particle size ranges when the rebound rate was the lowest.Figure 34 Table 12 Reference 77...