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initiation mechanism of Loess Mudflows by Flume Experiments

Journal of Earth Science 2022年第5期33卷 1166-1178页

作者： Penghui Ma Jianbing Peng Jianqi Zhuang Xinghua Zhu Cong Liu Yuxiang Cheng Zuopeng Zhang Key Laboratory of Western China Mineral Resources and Geological Engineering College of Geological Engineering and Surveying of Chang’an UniversityXi’an710054China Xi’an Engineering Investigation and Design Research Institute China Nonferrous Metals Industry Co.Ltd.Xi’an710054China

The structure of loess is loose,and the shear strength of loess drops sharply after contact with ***,loess mudflows have become a common geological disaster on the Chinese Loess *** order to study the initiation mode and mechanism of loess mudflows,in this study,seven sets of flume experiments were designed by controlling the slope angle and rainfall *** results show that(1)when the slope angle is between 10°and 20°,there are two initiation mechanisms of loess mudflows:mudflow(large scale)and retrogressive toe sliding,and mudflow(small-scale)and retrogressive toe sliding.(2)The main method by which water infiltrates into the soil accumulation is mainly vertical infiltration,which is not affected by the slope angle and the seepage direction of the accumulation soil.(3)The liquefaction of loess is the root cause of loess *** infiltrates into the area with an uneven density and a large amount of water accumulates in this ***,the water content of the loess increases and the pore water pressure increases quickly and cannot dissipate in time,so the loess liquefies and the liquefacted area continues to spread and become ***,loess mudflows(large scale)*** increase in pore water pressure was captured in the seven sets of ***,the order of the rising positions in the accumulation were *** requires us to carry out tracking of the particle displacement inside the soil and the spatial changes in the internal structure of the soil in future research.

关键词： flume tests loess mudflow loess liquefaction initiation modes initiation mechanism engineering geology

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Numerical Investigation on the initiation mechanism of Debris-Flow under Rainfall

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Journal of Mountain Science 2011年第4期8卷 619-628页

作者： LU Xiaobing YE Tianli CUI Peng HU Kaiheng CHEN Xiaoqing Institute of Mechanics Chinese Academy of Science Beijing 100084 China Institute of Mountain Hazards and Environment Chinese Academy of Science Chengdu 610041 China

Rainfall is an important factor to trigger the debris *** simulation on the responses of slopes and the initiation of debris flow under rainfall was processed by using the software FLAC2D based on the soil parameters in Weijia Gully,Beichuan County,Sichuan Province,*** effects of the slope angle,rainfall intensity,soil parameters on the developments of the stress and pore pressure and deformation of the slope were *** indicates that large displacements of the slope are mainly located near the slope *** the increase of the rainfall intensity the stability of the slope decreases and so the debris-flow is easy to occur.

关键词： Debris-flow initiation mechanism Rainfall Numerical simulation

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Field observation of debris-flow activities in the initiation area of the Jiangjia Gully, Yunnan Province, China

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Journal of Mountain Science 2022年第6期19卷 1602-1617页

作者： YANG Hong-juan ZHANG Shao-jie HU Kai-heng WEI Fang-qiang WANG Kai LIU Shuang Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610041China Chongqing Institute of Green and Intelligent Technology Chinese Academy of SciencesChongqing 400714China

The Jiangjia Gully, which is located in Dongchuan District, Yunnan Province, China, is a watershed prone to debris flows and has long-term recorded data of debris-flow occurrence. However, the initiation mechanism has mainly been studied by experiments in this watershed. To further reveal debris-flow formation mechanism in the Jiangjia Gully, debris-flow activities in the initiation zone were observed with hand-held video cameras in the summer of 2016 and 2017. In these two years, six debris-flow events were triggered in Menqian Gully, a major tributary of the Jiangjia Gully, while debrisflow activities in some sub-watersheds of Menqian Gully were recorded with video cameras in four events. The video recording shows that landslides constituted an important source for sediment supply in debris flow. Some landslides directly evolved into debris flows, while the others released sediment into rills and channels, where debris flows were generated for sediment entrainment by water flow. Therefore, debris-flow occurrence in the Jiangjia Gully is influenced both by infiltration-dominated processes and by runoff-dominated processes. In addition, rainfall data from four gauges installed in Menqian Gully were analyzed using mean intensity(I), duration(D), peak 10-minute rainfall(R10min) and antecedent rainfall(AR) up to 15 days prior to peak 10-minute rainfall. It reveals that debris-flow triggering events can be discriminated from nontriggering events either by an I-D threshold or by an R10min-AR threshold. However, false alarms can be greatly reduced if these two kinds of thresholds are used together. Moreover, behaviors including intermittency of debris flow, variance in moisture content and volume among surges, and coalescence of multiple surges by temporary damming were observed, indicating the complexity of debris-flow initiation processes. These findings are expected to enhance our knowledge on debris-flow formation mechanism in regions with similar environmental settin

关键词： Debris flow Field observation initiation mechanism Rainfall threshold Jiangjia gully

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A New View of the initiation and Propagation in Anionic Polymerization

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Chinese Journal of Chemistry 2013年第3期31卷 393-400页

作者： Anna Zheng Bo Chen Dihang Hu Yong Guan Dafu Wei Shuzhao Li Dandan Ji Shanghai Key Laboratory of Advanced Polymeric Materials Key Laboratory for Ultrafine Materials ofMinistry of Education School of Materials Science and Engineering East China University of Science and Technology Shanghai 200237 China

This work confirms the new view of the initiation and propagation mechanism of the anionic polymerization previously proposed, based on the investigation of anionic bulk-polymerization of styrene and α-methyl styrene with the help of a self designed microflow device and characterized by GPC and in situ ^7Li NMR. It was found that n-BuLl tended to form the hexameric-aggregated structure and even to form the huge aggregated structure based on the former. These aggregations of initiators could directly initiate the anionic polymerization and form the su-pramolecule aggregations. The supramolecule aggregations inevitably blocked the diffusion of the monomers to the ion-pairs and resulted in a stationary-conversion platform. Then the aggregators were dissociated completely into equal binary-aggregated species, and the polymerization continued again rapidly before the termination. Tetrahy-drofuran （THF） acted as the electron donator, which could push the electron cloud to Li cation and make the aggre- gated ring of the active species rather loosened and facilitated the monomer to insert in. Therefore, a little THF can greatly promote the anionic polymerization. However, further addition of THF might block the channel between the ion-pairs and decrease the propagation rate. It was also found that the aggregated structure of the active species during the anionic polymerization only depends on the initiator aggregations which were formed before the polym-erization.

关键词： anionic polymerization initiation mechanism in situ 7^Li NMR organolithium supramolecular aggre-gator

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Comparative Study on Debris Flow initiation in Limestone and Sandstone Spoil

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Journal of Mountain Science 2013年第2期10卷 190-198页

作者： CHEN Ning-sheng LU Yang DENG Ming-feng HAN Da-wei ZHOU Hai-bo YANG Cheng-lin Key lab of mountain hazards and surface process Institute of mountain hazards and environmentChinese Academy of Sciences University of Chinese Academy of Sciences University of Bristol UK

Large spoil tips from reconstruction works as a result of the Wenchuan Earthquake in China are new debris flow hazards to the human ***,there is a lack of detailed comparative study on debris flow initiation in different spoil *** paper describes a series of tests and analyses on debris flow characteristics(initiation,scale and mechanism) at six sites with limestone and sandstone materials near the Dujiangyan *** shows the limestone spoil contains debris flow prone clay content with high concentration of montmorillonite(highly expandable).In addition,limestone spoil is of such a low permeability that water mainly concentrates in the upper surface *** factors make it easy for the increase of pore water pressure,decline of internal friction and conhesion force,leading to the occurence of large debris *** contrast,the sandstone spoil is less problematic and causes no major debris flow *** on our research on the mechanism,the"stereometric drainage"method is sucessfully applied to control limestone spoil debris flows.

关键词： Debris flows Comparative study Reconstruction spoil initiation mechanism Mitigation measures

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VINYL RADICAL POLYMERIZATION INITIATED WITH CERIC ION AND ETHYL N, N-DIETHYLDITHIOCARBAMYL ACETATE SYSTEM

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Chinese Journal of Polymer Science 1997年第3期15卷 254-261页

作者：许守军丘坤元 Department of Polymer Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871

Acrylamide polymerization initiated with a redox initiation system consisting of eerie ion and ethyl N,N-diethyldithiocarbamyl acetate (EDCA) has been studied. It was found that the polymerization rate equation is in good agreement with that of a redox initiated polymerization, and the overall activation energy of the polymerization was determined to be 25.2 ***(-1). Accordingly, the system belongs to a redox initiator. The initiation mechanism was proposed based on the end group analysis using FT-IR, UV spectroscopies. Analysis results revealed that the N, N-diethyldithiocarbamyl radical produced from the redox reaction of EDCA with eerie ion can initiate acrylonitrile (AN) polymerization and form the end group on PAN. The resulting PAN was photopolymerized with butyl acrylate (BE) to form PAN-b-PBA block copolymer.

关键词： ceric ion redox initiator N,N-diethyldithiocarbamyl-end functional polymer block copolymerization initiation mechanism

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