Research On The Mechanism Of Spatial And Temporal Dust Dispersion And Prevention Measures For Earthwork Construction

Construction dust generates from construction sites and construction activities such as housing construction projects and municipal infrastructure projects,which is one of the main sources of atmospheric particulate matter.In recent years,with the rapid development of China’s construction industry,construction dust has become an important reason why the concentration of atmospheric particulate matter exceeds the standard one.Human’s lasting exposure to conditions where particulate matter concentrations exceeds the standard one may bring about a range of skin,respiratory and cardiovascular diseases,pose hazard to physical health as well as arise in economicproperty losses.To this end,the governments at the national and local levels have repeatedly introduced relevant policies and measures to address the problem of construction dust pollution,but the prevention effect is still to be improved.Relying on the topic of the 13 th Five-Year National Key R&D Program,or rather,Research and Demonstration of Pollutant Control Technology and Monitoring System during the Whole Process of Construction(2016YFC0702105),this thesis selects the construction dust generated on the earthwork construction stage as the study project,which is representative of the construction process,to conduct the research,and the main contents and conclusions are as follows.(1)Based on the characteristics of earth construction stages,a theoretical model of dust dispersion in earth construction was proposed and the calculation parameters of the model were confirmed.The wind tunnel test was used to reveal the law how wind speed,enclosure height,enclosure form and distance between enclosure and foundation pit boundary influenced dust diffusion velocity,dust concentration change and dust diffusion flow field characteristics of the earthwork.The study showed that strength of pollution source,wind speed and dust settling velocity were the main factors influencing dust diffusion concentration,and the greater the strength of pollution source,the lower the dust settling velocity and the higher the dust concentration at a certain distance away from the dust source.With the increasing of wind speed,the form of flow field maintained stable,but the velocity of dust sand particles and the initial concentration of dust dispersion increased.The construction fence would lead to significant changes in the dust diffusion flow field,and the vortex generated in the leeward area of the fence would lead to abrupt changes in parameters such as the transmission speed and dust concentration of the leaping dust after the fence.(2)The relationship between the calculation parameters and the influencing factors of the theoretical model for dust dispersion in earthwork construction was elucidated through numerical simulations to investigate the laws of dust spillage rate,average dispersion height,dust concentration and dust dispersion flow field characteristics under complex working conditions.The study showed that with the increasing of wind speed,the dust particle spill rate,average diffusion height and initial dust dispersion concentration also increased;the increasing of pit depth and the deployment of fence made the dust particle spill rate,average diffusion height and initial dust dispersion concentration decreaseto different extent.(3)The analysis of the measured data in the field revealed the influence of construction processes and prevention measures on the calculation parameters of the dust dispersion model for earthwork construction.The study showed that the higher the intensity of on-site construction at unit time was,the greater the strength of pollution source was,the more significant the tendency of construction dust diffusion was;prevention measures could effectively reduce the strength of pollution source and slow down the diffusion of construction dust;dust inside the construction site existed in the form of point source diffusion and had a superimposed effect.The results of wind tunnel tests,numerical simulations and on-site experiments showed that the theoretical model of dust dispersion for earthwork construction established by the research could accurately describe the dust dispersion mechanism on the relevant construction sites,and can also be used to predict the dust dispersion on such construction sites.(4)Assited by artificial intelligence methods,a model for predicting dust concentration on the construction sites under incomplete data conditions was established to achieve the accurate prediction of construction dust on the whole area of construction sites.A dust exposure occupational hazard model was constructed to analyze and quantify the dust exposure,health risks and occupational hazards of different types of workers on the construction site during earthwork construction,and rank the occupational health risks of on-site workers.(5)Based on the research results on construction dust dispersion law and hazards,the monitoring and evaluation indexes,standard limits,monitoring scheme and control measures for dust control on earthwork construction stage were proposed.Assisted by advanced technologies such as the Internet of Things,artificial intelligence methods and cloud computing,an intelligent control platform could be developed to monitor,warn and handle construction dust in real time.