| With the rapid development of urban traffic,ground traffic is almost saturated,and it is difficult to expand new ground roads.Therefore,the development of underground traffic has become an effective solution to urban traffic congestion.Due to the problems of large vibration,disturbance and noise in urban underground construction,the cantilever tunneling machine construction method originally applicable to mine construction can be used.However,the operation of TBM will produce a large amount of dust,which will seriously affect the tunnel operating environment and the health of construction personnel.How to effectively reduce dust has become a new research topic and engineering problem.Therefore,the air flow field,dust migration and diffusion law in the tunnel are studied and the surfactant is compounded to explore a comprehensive dust control method based on dry ventilation and dust removal in the tunnel and supplemented by dust reduction by spraying at the tunnel entrance.In thesis paper,the Hongshilu tunnel,which is mainly composed of sand and mudstone,is taken as the research object to study the fluid theory,and the wind flow field and dust distribution of the construction tunnel are further studied by using numerical model calculation,field measurement and proportional model test methods.The surfactant surface tension and spray dedusting experiments are conducted to configure the dedusting fluid.The research contents are as follows:(1)Based on the theory of gas-solid two-phase flow,the air flow field in the tunnel under actual construction conditions is studied by using Comsol software as the numerical simulation platform.According to the distribution of dust in the tunnel,the jet flow,return flow and eddy current in the air flow field will affect the movement of dust.The airflow with high wind speed will move together with the dust,which can effectively reduce the regional dust concentration;The airflow with general wind speed will make the dust overcome the influence of gravity and suspend in the air;The airflow with low wind speed has no obvious impact on the dust,and the dust is naturally precipitated by gravity.(2)Study the construction tunnel under the working condition of a single forced draught fan,explore the dust distribution law in the simple air flow field,and further demonstrate the impact of the air flow field on the dust.The space position,wind speed and distance from the tunnel face of the press in fan are taken as parameters for simulation,and it is concluded that when the press in fan is located at the arch shoulder,close to the dust source and kept at a certain position,the jet will carry the dust quickly towards the entrance,and the tunnel environment is the best.The ventilation and dust removal effect is the best when the wind speed is 14 m/s and the distance from the working face is 10 m.(3)Based on the tunnel working condition of the pressed fan with optimal parameters,the optimal space position of the exhaust fan is studied to enhance the ventilation and dust removal efficiency.The simulation found that when the suction fan and the pressure fan are at the same height and close to the dust source point,a strong U-shaped airflow will be formed in front of the tunnel face to intercept the dust from the dust source point and carry it out.The closer the ventilation is to the face and dust source,the stronger the Ushaped airflow is,which provides reference and guidance for guiding and optimizing the physical dust removal of ventilation and improving the tunnel environment.(4)The mechanism of dust suppression by spraying was studied,and the surfactant was studied and the surface tension was measured.It was found that the surface tension of the mixture of 0.05% anionic and non-ionic surfactant was closer to the limit tension of dust,and the walker wettability experiment was also the best.In the spray dust reduction experiment,its dust reduction capacity is the best,with dust reduction up to68%,providing a dust remover configuration scheme for construction spray dust reduction. |
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