With high spatial resolution,on-demand-flying ability,and the capacity for obtaining threedimensional measurements,unmanned aerial vehicle(UAV)photogrammetry is widely used for detailed investigations of single landsl...With high spatial resolution,on-demand-flying ability,and the capacity for obtaining threedimensional measurements,unmanned aerial vehicle(UAV)photogrammetry is widely used for detailed investigations of single landslides,but its effectiveness for landslide detection and monitoring in a large area needs to be investigated.The Heifangtai terrace in the Loess Plateau of China is a loess terrace that is extremely susceptible to irrigation-induced loess landslides.This paper used UAV-based photogrammetry for a series of highresolution images spanning over 30 months for landslide detection and monitoring of the terrace with an area of 32 km^2.Dense and evenly distributed ground control points were established and measured to ensure the high accuracy of the photogrammetry results.The structure-from-motion(Sf M)technique was used to convert overlapping images into orthographic images,3D point clouds,digital surface models(DSMs)and mesh models.Using multitemporal differential mesh models,landslide vertical movements and potential landslides were detected and monitored.The results indicate that a combination of UAV-based orthophotos and differential mesh models can be used for flexible and accurate detection and monitoring of potential loess landslides in a large area.展开更多
With the rapid development of urbanization, a large amount of construction spoil was stockpiled around cities and formed extensive dumps. Construction spoil is one of the main construction and demolition(C&D) wast...With the rapid development of urbanization, a large amount of construction spoil was stockpiled around cities and formed extensive dumps. Construction spoil is one of the main construction and demolition(C&D) waste and municipal solid waste(MSW). Once the construction spoil dump becomes unstable, it will bring great risks to the surrounding residents. A catastrophic dump failure occurred on 20 December 2015 in Guangming New Strict, Shenzhen, China. Approximately 2.51×10^(6) m^(3) of construction waste slid out from the dumpsite, destroying 33 houses and causing total 77 casualties. This paper attempts to analyze the failure probability of the construction spoil dump using Monte Carlo simulation considering the spatial variability of soil properties, and to quantify the dynamic human risk considering the increasing urbanization. Influence of urbanization on the human element at risk is analyzed by referring to multi-temporal remote sensing images. A quantitative human risk assessment model is employed to determine the landslide human risk referring an assessment criteria curve between frequency of number fatalities and number of fatalities(F-N curve). It is found that the societal risk at daytime was 0.078, 0.088, and 1.432 in 2002, 2014, and 2015, respectively. Meanwhile, the societal risk at night was 0.034, 0.037, and 0.611 in 2002, 2014, and 2015, respectively. The quantitative method was benchmarked by the other landfill failure. It implies that the human risk increased with the development of urbanization and its value at daytime was approximately twice as much as at night. The new approach for the human risk assessment provides guidance for modern MSW landfills and highlights the obvious influence of urbanization on the human risk in other areas.展开更多
On the strength of expounding the general situation of study area and the status quo of agricultural laborers in China,the changes of the scale and structure of agricultural laborer from 1985 to 2009 are analyzed by r...On the strength of expounding the general situation of study area and the status quo of agricultural laborers in China,the changes of the scale and structure of agricultural laborer from 1985 to 2009 are analyzed by relying on the survey from farmers and statistical data from the government.The causes of these changes are analyzed from the aspects of rural farmland policy,birth-control policy,farmland marginalization and industrialization.Based on the study on the causes,the impacts of the changes on food production are analyzed from operation scale of household,the grain cropping area,the multi-cropping index and land productivity.The results show that the quality of agricultural laborers is decreasing form 1985 to 2009,which is characterized by the lack of middle-aged agricultural laborers and the aging of agricultural laborers.The causes of the changes include farmland policy,birth-control policy,farmland marginalization and urbanization.The shrinkage of agricultural laborers has grave impact on the multiple-cropping index.In addition,the land productivity is comprehensively affected by the scale and structure of agricultural laborers.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41521002,41941019,41630640)the Major R&D projects of Sichuan Science and Technology Plan(Grant No.2018SZ0339)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(Grant No.SKLGP2014Z004)。
文摘With high spatial resolution,on-demand-flying ability,and the capacity for obtaining threedimensional measurements,unmanned aerial vehicle(UAV)photogrammetry is widely used for detailed investigations of single landslides,but its effectiveness for landslide detection and monitoring in a large area needs to be investigated.The Heifangtai terrace in the Loess Plateau of China is a loess terrace that is extremely susceptible to irrigation-induced loess landslides.This paper used UAV-based photogrammetry for a series of highresolution images spanning over 30 months for landslide detection and monitoring of the terrace with an area of 32 km^2.Dense and evenly distributed ground control points were established and measured to ensure the high accuracy of the photogrammetry results.The structure-from-motion(Sf M)technique was used to convert overlapping images into orthographic images,3D point clouds,digital surface models(DSMs)and mesh models.Using multitemporal differential mesh models,landslide vertical movements and potential landslides were detected and monitored.The results indicate that a combination of UAV-based orthophotos and differential mesh models can be used for flexible and accurate detection and monitoring of potential loess landslides in a large area.
基金This study was funded by the National Key R&D Program of China(Grant Nos.2019YFC1806001,2018YFC1802301)the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.41907243)the Research Grants Council of the Hong Kong Special Administrative Region,China(Project No.UGC/FDS25/E11/17)。
文摘With the rapid development of urbanization, a large amount of construction spoil was stockpiled around cities and formed extensive dumps. Construction spoil is one of the main construction and demolition(C&D) waste and municipal solid waste(MSW). Once the construction spoil dump becomes unstable, it will bring great risks to the surrounding residents. A catastrophic dump failure occurred on 20 December 2015 in Guangming New Strict, Shenzhen, China. Approximately 2.51×10^(6) m^(3) of construction waste slid out from the dumpsite, destroying 33 houses and causing total 77 casualties. This paper attempts to analyze the failure probability of the construction spoil dump using Monte Carlo simulation considering the spatial variability of soil properties, and to quantify the dynamic human risk considering the increasing urbanization. Influence of urbanization on the human element at risk is analyzed by referring to multi-temporal remote sensing images. A quantitative human risk assessment model is employed to determine the landslide human risk referring an assessment criteria curve between frequency of number fatalities and number of fatalities(F-N curve). It is found that the societal risk at daytime was 0.078, 0.088, and 1.432 in 2002, 2014, and 2015, respectively. Meanwhile, the societal risk at night was 0.034, 0.037, and 0.611 in 2002, 2014, and 2015, respectively. The quantitative method was benchmarked by the other landfill failure. It implies that the human risk increased with the development of urbanization and its value at daytime was approximately twice as much as at night. The new approach for the human risk assessment provides guidance for modern MSW landfills and highlights the obvious influence of urbanization on the human risk in other areas.
基金Supported by the Humanity and Social Science Programs of Hubei Provincial Department of Education(2009Y149)the Project of Excellent Middle-aged People and Young People Team in Colleges and Universities of Hubei Province(T200708)
文摘On the strength of expounding the general situation of study area and the status quo of agricultural laborers in China,the changes of the scale and structure of agricultural laborer from 1985 to 2009 are analyzed by relying on the survey from farmers and statistical data from the government.The causes of these changes are analyzed from the aspects of rural farmland policy,birth-control policy,farmland marginalization and industrialization.Based on the study on the causes,the impacts of the changes on food production are analyzed from operation scale of household,the grain cropping area,the multi-cropping index and land productivity.The results show that the quality of agricultural laborers is decreasing form 1985 to 2009,which is characterized by the lack of middle-aged agricultural laborers and the aging of agricultural laborers.The causes of the changes include farmland policy,birth-control policy,farmland marginalization and urbanization.The shrinkage of agricultural laborers has grave impact on the multiple-cropping index.In addition,the land productivity is comprehensively affected by the scale and structure of agricultural laborers.
