Numerical Simulation Study About The Dust Reduction Effect Of Fence During The Construction Phase Of Foundation Pit In Constructional Engineering

Today,with the improvement of social productivity,the quality of life of residents in our country has been improved unprecedentedly.However,problems such as uncoordinated development,inadequate development,and unsustainability still exist,such as environmental problems that are closely related to people’s lives.In recent years,the smog caused by sandstorms,automobile exhaust,industrial and agricultural smoke,and construction dust has seriously affected the normal life of the people,the normal production of society,and the health of residents;among them,construction dust is gradually becoming The leading factor leading to air quality pollution,but as long as the measures are taken properly,it is relatively easy to artificially control construction dust.The foundation pit construction stage is the stage with the largest and densest dust production in construction.Construction enclosures,as the curing measures specified in the specifications,have played a huge role in controlling construction dust.However,there are few research results on the effect of enclosure dust reduction during the construction of foundation pits,so that There are relatively few theories and suggestions for setting dust in earthwork operations.In this paper,based on the 13 th Five-Year Key Research and Development Plan "Research and Demonstration of Pollutant Control Technology and Monitoring System in the Whole Process of Construction",relying on the demonstration project in Kaifu District of Changsha City,using ANSYS FLUENT simulation software,respectively Conducted Numerical simulation analysis of construction conditions that affect the dust reduction effect of the enclosure,and numerical simulation analysis of the optimization of the enclosure itself in the construction project foundation pit construction stage;based on the simulation analysis results,some reasonable measures that can match production needs are proposed.And formed some important conclusions as follows:The analysis of the wind field with or without enclosures shows that the wind speed in the working area of the foundation pit is less than the wind speed in the non-operating area,and the wind speed in the foundation pit is significantly smaller than the external wind speed.The setting of the enclosure will further attenuate the airflow speed in the foundation pit.In addition,the analysis of the particle motion characteristics found that the particle motion has obvious airflow followability.In the calculation domain,the maximum particle concentration appears near the lower wall of the enclosure,and the setting of the enclosure will increase the overflow point,which will increase the maximum diffusion height of the particles.The cross section of 0.5m outside the enclosure was removed,and the influence of wind speed and particle size on the dust reduction of the enclosure was analyzed.The results show that relative to the particle size,wind speed is the main factor affecting the maximum particle concentration and particle overflow rate.For the maximum particle diffusion height and particle escape rate,the wind speed and particle size are the main factors affecting its change.For a constant dust source and a large inlet wind speed,the increase in wind speed will disperse the particle distribution outside the enclosure to reduce the maximum particle concentration,increase the maximum particle diffusion height,increase the particle overflow rate and remote escape rate.Due to the influence of factors such as gravity and volume buoyancy,the increase in particle size will reduce the maximum particle concentration,maximum particle diffusion height,particle overflow rate and particle remote escape rate.Taking the height of the enclosure as the influencing factor,the dust reduction effect under the enclosure conditions of 1m,1.8m,2.5m,3.5m and 4.5m was studied.The results show that the increase of enclosure will change the wind field in the calculation domain,but it is beneficial to Suppress dust in foundation pit construction.Further analysis found that as the height of the enclosure increases,the particle overflow rate and escape rate continue to decrease,but when the enclosure height is greater than 3.5m,the particle overflow rate and escape rate basically do not change,so 3.5m is roughly controlled The ultimate containment height of particles overflowing and escaping.In addition,2.5m is the sensitive turning height of the enclosure for controlling the maximum concentration of particles and the maximum diffusion height.When the enclosure height is less than 2.5,with the increase of the enclosure,the maximum concentration of particles decreases slowly,and the maximum diffusion height of the particles is basically Theris not much fluctuation;when the height of the enclosure is greater than 2.5m,with the increase of the enclosure,the maximum particle concentration is greatly reduced,and the maximum diffusion height of the particles is greatly increased.By increasing the height of the enclosure in different directions,the setting form of unequal height enclosure was formed,and the dust-reducing effect of the enclosure in different orientations was studied.The results show that increasing the height of the enclosure in any direction alone is conducive to strengthening the suppression of spillage and escape of particles,and the control effect of the upper enclosure is the most obvious,followed by the lower enclosure and the side enclosure.Moreover,the height of the side enclosure is lower than the height of the upper and lower enclosures is conducive to controlling the dust in the foundation pit.Therefore,It is the most reasonable form of enclosure that the height of the upper and lower enclosures is greater than the height of the side enclosures.