Research On Formation,Diffusion And Controlling Of Construction Dust

With the rapid development of the national economy,large-scale construction of traffic roads,municipal projects,and civil buildings,while promoting social and economic development,it has also brought a lot of pollution to the natural environment.Air pollution has become one of the most important environmental issues facing our country.Monitoring data show that total suspended particulate matter(TSP),inhalable particulate matter(PM10)and fine particulate matter(PM2.5)have become the primary pollutants of urban air pollution in China.The main sources of these particulate pollutants include construction dust at construction sites.The foundation pit support and earth and stone construction stages during the construction process of the construction site have the characteristics of huge project volume,long pit excavation operation time,large-scale construction machinery concentration,large disturbance to natural bare soil,etc.It has become the main source of construction dust pollution caused by the surrounding environment of the construction site.This article takes the dust generated during construction activities as the research object,and explores the related laws of construction dust formation and diffusion.Taking the green construction environmental protection as the goal,it provides theoretical and practical basis for the measurement and control of dust.Relying on gas-solid two-phase flow theory,CFD(Computational Fluid Dynamics)method was used to simulate the diffusion process of construction dust.It provides reference and reference for dust diffusion simulation and dust monitoring and control at the construction site,and the following conclusions are obtained.(1)Based on extensive research of dust particle diffusion laws at home and abroad and construction dust pollution control research,the theoretical research results of dust diffusion have been summed up,and the source of construction dust during the four construction phases has been analyzed.The CFD numerical simulation method was used to simulate the diffusion process of construction dust.(2)Through the simulation of the distribution of wind field in the foundation pit under the conditions of three different foundation pits of 4,8,and 12 m and three different wind speeds of 3,4.5,6,7.5,and 9m/s,the change law of the wind field in the foundation pit with the depth of the foundation pit and the wind speed is obtained.There is a swirling airflow in the upwind direction of the foundation pit,and this area is also expanding with the increase of depth or the increase of wind speed,the impact on dust particles is also greater.In the downwind direction of the foundation pit,the airflow encounters obstacles to the foundation pit wall,and the wind direction changes to form an ascending airflow,forming an acceleration zone.It is the main escape area for dust particles.(3)Through the analysis of the change of dust particle mass concentration cloud map of a foundation pit with a depth of 8m under the airflow of 6 m/s,the diffusion law of dust particles in the foundation pit under the action of wind force is obtained.The dust particles on the upwind side of the foundation pit converge at the upward wind direction and rise along the foundation pit wall due to the influence of the vortex area.The dust particles in the middle of the foundation pit move along the direction of the air flow to the wind direction under the foundation pit.The dust particles in the downwind direction of the foundation pit are affected by the updraft near the foundation pit wall,rise along the foundation pit wall and spread to the outside of the foundation pit,and continue along the direction of the airflow velocity vector in the downward direction of the wind direction along the foundation pit.(4)Through the analysis of the change of dust particles’ mass concentration at the height of 2.5m in the area within 100 m from the downwind edge of the foundation pit under the conditions of three different foundation pits of 4,8,and 12 m and three different wind speeds of 3,4.5,6,7.5,and 9m/s,the diffusion of dust particles from the side of the foundation pit to the perimeter of the site was simulated.In different pit depths and different wind speed conditions.The variation of dust particle mass concentration with the distance to the foundation pit is consistent,both showing the trend of increasing first and then decreasing.The diffusion model of dust particles is obtained by data regression.(5)Combining the diffusion law of dust particles,From the perspective of reducing the impact of construction sites on the surrounding environment,a more optimized measure of construction dust measurement and pollution control has been proposed.