Page 90 - 水利学报2021年第52卷第2期

Path planning of gravel soil paving based on cellular automata and improved A* algorithm

JIAO Zheng，WANG Jiajun，WANG Xiaoling，CUI Bo，TONG Dawei，GUAN Tao
（State Key Laboratory of Hydraulic Engineering Simulation and Safety，Tianjin University，Tianjin 300072，China）

Abstract： Gravel paving is an important part of the construction of core rockfill dams， and its thickness
and flatness are key indicators to characterize the paving quality. However， the existing paving operation
path planning highly relies on manual experience and has the disadvantage of strong subjectivity， so it is
difficult to effectively control the paving quality. Aiming at the above problems， this research proposes a
path planning method for paving gravel soil based on cellular automata and improved A* algorithm. This
method optimizes the selection of the global path by improving the trajectory distance measurement function
in the A* algorithm and introducing the obstacle avoidance redundant distance. At the same time， it com⁃
bines the quality evaluation function to optimize the local dynamic path planning method， so as to realize
the global-local hybrid path planning of the paving operation. In addition，by establishing a cellular automa⁃
ta model for the paving quality of gravel soil， the real-time monitoring data of the construction machinery
is converted into the quality information of each grid of the working surface，so the quality information can
be updated in real time. Engineering application shows that the method proposed in this study can control
the paving thickness at about 0.27 m on the premise of ensuring construction efficiency，effectively avoiding
the occurrence of ultra-thick and ultra-thin phenomena， and the flatness is improved by 22.6% compared
with manual work.
Keywords：gravel soil paving；cellular automata；hybrid path planning；A* algorithm；real time monitoring
（责任编辑：李福田）
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A review on the mechanism of nitrogen loss and its effected factors in the open nature water

1，2 1 1，2 1 2 1
YANG Zhengjian ，WEI Chenyu ，LIU Defu ，JI Daobin ，MA Jun ，WANG Congfeng
（1. Hubei Observation and Research Station of Three Gorges Reservoir Ecosystem，
China Three Gorges University，Yichang 443002，China；
2. Hubei Key Laboratory of Ecological Restoration of River-lakes and Algal Utilization，
Hubei University of Technology，Wuhan 430068，China）

Abstract：In China，nearly 100，000 reservoirs of various types have been built，which changed the origi⁃
nal hydrodynamic and biogeochemical conditions of rivers，affecting the material，energy，chemical and bio⁃
logical fields of water bodies. However， it is still unclear whether the reservoirs reduce water purification
function or strengthen the water decontamination capacity. In this study，some researches on nitrogen remov⁃
al in natural open water areas were summarized and found that （1） Anaerobic denitrification，anaerobic am⁃
monium oxidation，aerobic denitrification and anaerobic methane oxidation are four typical processes of deni⁃
trification of open water body；（2） nitrogen removal could happen mainly in some anaerobic areas， such
as hyporheic zone， sediment layer， oxygen minimum zone and suspended particle； and （3） dissolved oxy⁃
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gen （DO）， carbon-nitrogen ratio （C/N）， nitrate concentration （NO 3）， temperature and pH are the direct
factors affecting the efficiency of denitrification in open water. Based on those above，four suggestions were
given in this paper for further researches on the effects of reservoirs on nitrogen removal， which contained
continuous monitoring of different nitrogen formation and calculation of nitrogen load balance， the in-situ
methodology on denitrification mechanism of different carriers in reservoirs， and the denitrification mecha⁃
nism and nitrogen removal flux in reservoirs and comparative research on the nitrogen removal efficiency be⁃
tween natural rivers and reservoirs.
Keywords： nitrogen removal； hyporheic zone； sediment layer； oxygen minimum zone； suspended particle；
reservoir
（责任编辑：杨 虹）

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