Wind Tunnel Test And Numerical Simulation Of Wind Sand Flow Field Around Building Foundation Pit

In recent years,with the rapid development of the national economy and the largescale construction of municipal projects and civil buildings,the problem of environmental pollution has become increasingly prominent.In the construction,especially in the foundation pit construction stage,a large amount of dust,as an important part of urban dust,not only causes pollution to the atmospheric environment,but also seriously endangers human health.At the same time,construction enterprises will face the problem of forced shutdown.It is of great practical significance to study the law of dust diffusion during foundation pit construction.This paper is based on the 13 th five-year national key research and development project "research and demonstration of pollutant control technology and monitoring system in the whole process of construction"(No.2016YFC0702105),and on the premise of the research status,the diffusion process of dust particulate pollutants was studied from the wind field characteristics of the area where the dust particulate pollutants were located.In this paper,the wind tunnel test and numerical simulation were used to study the wind sand flow field around the foundation pit.Firstly,the basic characteristics of wind field and sand behavior were described through wind tunnel tests,and the effects of the distance between retaining wall and the edge of foundation pit and the height of retaining wall on wind field and particle concentration were analyzed.The influence of the distance of the fence and the depth of the foundation pit on the dust suppression of the fence is further analyzed and the wind sand environment of the pedestrian height are further analyzed by numerical simulation method.Finally,some suggestions are put forward.The main conclusions are as follows:(1)It can be obtained by wind tunnel test: 1)The length of the ground in the rear covering area of the enclosure is approximately 6 times the height of the enclosure;2)The essence of dust suppression is to change the movement state of sand grains by changing the wind field environment around it;3)With the increase of the distance between the retaining wall and the edge of the foundation pit,the maximum reduction rate of the airflow behind the retaining wall is 70%;4)With the increase of the barrier height,the maximum reduction rate of airflow behind the barrier is 73%,and the maximum particle concentration behind the barrier gradually decreases;(2)The numerical calculation model is established: standard k-? model was used for gas phase movement,and discrete phase model was used for dust particles.By comparing the numerical results with the wind tunnel test results,the correlation coefficients of the flow velocity profile curves are all greater than 0.87,which verifies the accuracy of the numerical model(3)It can be obtained by numerical simulation: 1)With the increase of the distance between the retaining wall and the edge of the foundation pit,the average particle concentration outside the retaining wall decreases,the maximum particle diffusion height increases first and then decreases,the overflow decreases first and then increases,when the enclosure is set at 10 m away from the edge of the foundation pit,the dust suppression effect is the best;2)With the increase of foundation pit depth,the average particle concentration increases slightly first and then decreases,the maximum particle diffusion height decreases,and the overflow rate decreases,dust control measures such as spraying should be taken when the depth of foundation pit is shallow;3)In the pedestrian height plane,along the flow direction,the particle concentration decays rapidly at first and then presents a certain fluctuation,and the fluctuation value remains within a small range,the diffusion of dust particles within 12 m outside the enclosure should be controlled.