In order to solve the problem of poor environmental protection in the process of traditional dredging, the pneumatic pump has been introduced into the city's inner lake dredging projects. Based on field process optimization, dredging accuracy and diffusion range monitoring analysis, the following conclusions are given: the formed pneumatic pump dredging process has the advantages of micro-turbulent & high-precision; the lake bottom elevation accuracy of the dredging process is controlled within 0.05m, and the increase of suspended matter 10m away from the boat is less than 10 mg/L.
The city's inner lake has poor fluidity, and affected by the influx of domestic sewage, which lead to serious pollution (Zheng, 2020). Traditional dredging equipment such as grabs, water excavators, and small cutter suction boats have poor environmental protection during dredging. The main problems are poor dredging accuracy, large water disturbances, and inevitable secondary pollution (Liu, 2020, Wang, 2016, Yuan, 2020, Liu, 2018).
At present, in the field of dredging, only the standard of ‘Design code for dredging and reclamation works’ (Ministry of Transport of the People's Republic of China, 2012) has stipulated the increase of suspended sediment caused by the dredging process when it is adjacent to aquaculture areas, and it is required that the increase should not be greater than 10mg/L. Environmental protection dredging technology currently mainly includes Pneumatic pump, small cutter suction vessels with environmental protection covers, anti-fouling curtains arranged in dredging waters, and flocculant spraying during the dredging process (Wei, 2019, Wei, 2021).
Pneumatic pump is an environmentally friendly dredging equipment that uses negative pressure to suck in bottom sludge and transports it by air as power.At present, this equipment has not been widely used in urban lake dredging projects, and the construction technology of pneumatic pump ships has not been formed. The disturbance range and dredging accuracy of different construction process parameters and pump head structure are compared and analyzed, based on the aerial photography of the pneumatic pump construction process, the micro-disturbance monitoring of water sampling and the measured data of the terrain elevation after dredging,in the contaminated sediment dredging project of Yundang Lake in Xiamen City, Fujian Province, China.
