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Failure criteria of unreinforced masonry walls of rural buildings under the impact of flash floods in mountainous regions

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Journal of Mountain Science 2022年第12期19卷 3388-3406页

作者： SI Guang-wu CHEN Xiao-qing CHEN Jian-gang ZHAO Wan-yu LI Shuai LI Xiang-ning Key laboratory of Mountain Hazards and earth surface process Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu610041China China-Pakistan Joint Research Center on earth Sciences CAS-HECIslamabad45320Pakistan University of Chinese Academy Sciences Beijing100049China

Damage to rural buildings in mountainous regions caused by flash floods accounts for a significant proportion of economic losses from *** unreinforced masonry(URM)wall is the most vulnerable structural element of rural buildings exposed to flash *** failure of a URM wall indicates damage to rural buildings in flash *** on the yield line theory of out-of-plane damage of URM walls and the virtual work method,brittle failure criteria for URM walls under the impact of flash floods were *** to the field investigation data of the 26 June 2020 flash flood event in Damawu Gully and the corresponding simulation results of FLO-2D,the disaster-causing process was analysed,and the failure criteria were *** building parameters were identified to influence the flood-resistance of URM walls,including the mortar grade,the span-to-height ratio of the wall,and the number of floors of the rural *** results showed that the cause of the 26June disaster was the diversion of a 50-year flash flood into the residential community on the alluvial *** affected buildings were constructed with hollow blocks and lacked flood-resistance *** critical failure depth of a URM wall restrained at the top by ring beams(RBs)under hydrostatic load conditions is 1.17 to 1.20 times greater than that of a URM wall without RBs,and the difference is even more pronounced when lowerstrength mortar is *** flood-resistance of a URM wall constructed with Mb 7.5 mortar and restrained by RBs is almost as strong as that of a URM wall constructed with Mb 20 mortar and without *** span-to-height ratio of a URM wall should not be greater than 1.875 in this ***,the flood-resistance of a URM wall with RB restraint is almost independent of the span-to-height *** brittle fracture energy of masonry mortar is more crucial to the flood-resistance of 4-edge restrained URM walls if L/Z>*** flood-resistance of the URM wa

关键词： Flash flood Rural buildings Unreinforced masonry wall Failure criteria Flood-resistance

Impact failure models and application condition of trees in debris-flow hazard mitigation

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Journal of Mountain Science 2021年第7期18卷 1874-1885页

作者： JIN Ke CHEN Jian-gang CHEN Xiao-qing ZHAO Wan-yu SI Guang-wu GONG Xing-long Key laboratory of Mountain Hazards and earth surface process Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610041China China-Pakistan Joint Research Center on earth Sciences CAS-HECIslamabad 45320Pakistan University of Chinese Academy Sciences Beijing 100049China

Forestry has played an important role in hazard mitigation associated with debris *** forest mitigation measures refer to the experience of soil and water conservation,which disregard the destructive effect of debris flows,causing potentially serious *** of the effect of a forest on reducing debris-flow velocity and even stopping debris flows requires distinguishing between when the debris flow will destroy the forest and when the trees will withstand the debris-flow impact *** this paper,we summarized two impact failure models of a single tree: stem breakage and *** influences of different tree sizes characteristics(stem base diameter,tree weight,and root failure radius) and debris-flow characteristics(density,velocity,flow depth,and boulder diameter) on tree failure were *** observations obtained from the model adopted in this study show that trees are more prone to stem breakage than *** an increase in tree size,the ability to resist stem breakage and overturning ***-flow density influences the critical failure conditions of trees substantially less than the debrisflow velocity,depth,and boulder *** application conditions of forests in debris-flow hazard mitigation were proposed based on the analysis of the model *** proposed models were applied in the Xiajijiehaizi Gully as a case study,and the results explain the destruction of trees in the forest dispersing *** work provides references for implementing forest measures for debris-flow hazard mitigation.

关键词： Trees Impact failure model Forest application condition Debris flow mitigation

Hydraulic mechanism and time-dependent characteristics of loose gully deposits failure induced by rainfall

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第6期7卷 708-715页

作者： Yong Wu Siming He Key laboratory of Mountain Hazards and earth surface process Chinese Academy of Sciences Institute of Mountain Hazards and environment Chinese Academy of Sciences State Key laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of Technology

Failure of loose gully deposits under the effect of rainfall contributes to the potential risk of debris *** the past decades, researches on hydraulic mechanism and time-dependent characteristics of loosedeposits failure are frequently reported, however adequate measures for reducing debris flow are notavailable practically. In this context, a time-dependent model was established to determine the changesof water table of loose deposits using hydraulic and topographic theories. In addition, the variation inwater table with elapsed time was analyzed. The formulas for calculating hydrodynamic and hydrostaticpressures on each strip and block unit of deposit were proposed, and the slope stability and failure risk ofthe loose deposits were assessed based on the time-dependent hydraulic characteristics of establishedmodel. Finally, the failure mechanism of deposits based on infinite slope theory was illustrated, with anexample, to calculate sliding force, anti-sliding force and residual sliding force applied to each slice. Theresults indicate that failure of gully deposits under the effect of rainfall is the result of continuouslyincreasing hydraulic pressure and water table. The time-dependent characteristics of loose depositfailure are determined by the factors of hydraulic properties, drainage area of interest, rainfall pattern,rainfall duration and intensity.

关键词： Loose deposits Time-dependent characteristics Groundwater lever Hydraulic mechanism

Effects of dielectric decrement on surface potential in a mixed electrolyte solution

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Chinese Physics B 2018年第12期27卷 436-443页

作者： Jing Peng Wen-Xin Zou Rui Tian Hang Li Xin-Min Liu Chongqing Key laboratory of Soil Multiscale Interfacial process College of Resources and EnvironmentSouthwest University

surface potential is an important parameter related to the physical and chemical properties of charged particles. A simple analytical model for the estimation of surface potential is established based on the Poisson–Boltzmann theory with the consideration of the dielectric decrement in mixed electrolyte. The analytical relationships between surface potential and charge density are derived in different mixed electrolytes with monovalent and bivalent ions. The dielectric decrease on the charged surface strongly affects the surface potential at a high charge density with different ion strengths and concentration ratios of counter-ions. The surface potential based on the Gouy–Chapman model is underestimated because of the dielectric decrement on the surface. The diffuse layer can be regarded as a continuous uniform medium only when the surface charge density is lower than 0.3 C·m-2. However, the surface charge densities of many materials in practical applications are higher than 0.3 C·m-2. The new model for the estimation of surface potential can return to the results obtained based on the Gouy–Chapman model at a low charge density. Therefore, it is implied that the established model that considers the dielectric decrement is valid and widely applicable.

关键词： surface potential colloidal particle dielectric decrement charge density electrolyte

Assessment of prospective hazards resulting from the 2017 earthquake at the world heritage site Jiuzhaigou Valley, Sichuan, China

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Journal of Mountain Science 2018年第4期15卷 779-792页

作者： CHEN Xiao-qing CHEN Jian-gang CUI Peng YOU Yong HU Kai-heng YANG Zong-ji ZHANG Wei-feng LI Xin-po WU Yong Key laboratory of Mountain Hazards and earth surface process Institute of Mountain Hazards and Environment Chinese Academy of Sciences (CAS) Chengdu 610041 China CAS Center for Excellence in Tibetan Plateau earth Sciences Beijing 100101 China Youth Innovation Promotion Association CAS Beijing 100029 China

On August 8, 2017, a Ms = 7.0 magnitude earthquake occurred in the Jiuzhaigou Valley, in Sichuan Province, China(N: 33.20°, E: 103.82°). Jiuzhaigou Valley is an area recognized and listed as a world heritage site by UNESCO in 1992. Data analysis and field survey were conducted on the landslide, collapse, and debris flow gully, to assess the coseismic geological hazards generated by the earthquake using an unmanned aerial vehicle(UAV), remote-sensing imaging, laser range finders, geological radars, and cameras. The results highlighted the occurrence of 13 landslides, 70 collapses, and 25 potential debris flow gullies following the earthquake. The hazards were classified on the basis of their size and the potential property loss attributable to them. Consequently, 14 large-scale hazards, 30 medium-sized hazards, and 64 small hazards accounting for 13%, 28%, and 59% of the total hazards, respectively, were identified. Based on the variation tendency of the geological hazards that ensued in areas affected by the Kanto earthquake(Japan), Chi-chi earthquake(Taiwan China), and Wenchuan earthquake(Sichuan China), the study predicts that, depending on the rain intensity cycle, the duration of geological hazard activities in the Jiuzhaigou Valley may last over ten years and will gradually decrease for the following five to ten yearsbefore returning to pre-earthquake levels. Thus,necessary monitoring and early warning systems must be implemented to ensure the safety of residents,workers and tourists during the construction of engineering projects and reopening of scenic sites to the public.

关键词： 2017 Jiuzhaigou earthquake Disaster risk Geological hazard Landslide World heritage site Jiuzhaigou Valley

Estimation of Shallow Landslide Susceptibility Incorporating the Impacts of Vegetation on Slope Stability

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International Journal of Disaster Risk Science 2023年第4期14卷 618-635页

作者： Hu Jiang Qiang Zou Bin Zhou Yao Jiang Junfang Cui Hongkun Yao Wentao Zhou Key laboratory of Mountain Hazards and earth surface process Institute of Mountain Hazards and Environment(IMHE)Chinese Academy of Sciences(CAS)Chengdu 610041China China-Pakistan Joint Research Center on earth Sciences Islamabad 45320Pakistan University of Chinese Academy of Sciences Beijing 100049China

This study aimed to develop a physical-based approach for predicting the spatial likelihood of shallow landslides at the regional scale in a transition zone with extreme *** landslide susceptibility study in an area with diverse vegetation types as well as distinctive geographic factors(such as steep terrain,fractured rocks,and joints)that dominate the occurrence of shallow landslides is *** article presents a novel methodology for comprehensively assessing shallow landslide susceptibility,taking into account both the positive and negative impacts of *** includes considering the positive efects of vegetation canopy interception and plant root reinforcement,as well as the negative efects of plant gravity loading and preferential fow of root *** approach was applied to simulate the regional-scale shallow landslide susceptibility in the Dadu River Basin,a transition zone with rapidly changing terrain,uplifting from the Sichuan Plain to the Qinghai–Tibet *** research fndings suggest that:(1)The proposed methodology is efective and capable of assessing shallow landslide susceptibility in the study area;(2)the proposed model performs better than the traditional pseudo-static analysis method(TPSA)model,with 9.93%higher accuracy and 5.59%higher area under the curve;and(3)when the ratio of vegetation weight loads to unstable soil mass weight is high,an increase in vegetation biomass tends to be advantageous for slope *** study also mapped the spatial distribution of shallow landslide susceptibility in the study area,which can be used in disaster prevention,mitigation,and risk management.

关键词： Physical-based model Qinghai-Tibet Plateau Shallow landslide Susceptibility analysis Vegetation effect

Applications of mercury stable isotopes for tracing volcanism in the geologic record

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Science China earth Sciences 2024年第5期67卷 1436-1458页

作者： Qing GONG Ming-Xing LING Wang ZHENG State Key laboratory of Nuclear Resources and environment East China University of TechnologyNanchang 330013China School of earth System Science Institute of Surface-Earth System ScienceTianjin UniversityTianjin 300072China

Mercury(Hg)enrichments in ancient sediments have been used as a proxy of volcanism,especially large igneous province(LIP)***,considering the existence of other potential Hg sources besides volcanoes and the diverse factors(e.g.,organic matters,clay minerals,sulfide minerals and Fe oxides)that can affect Hg sequestration,there are considerable uncertainties to simply regard sedimentary Hg anomalies as signatures of volcanic *** stable isotopes,a promising tool for tracing the origins and transformations of Hg,have been increasingly used for determining the causes of Hg spikes and understanding the geochemical behavior of Hg in the geologic *** date,lots of researches have applied Hg concentrations and Hg isotopes to identify LIP volcanisms linking with significant geological events such as mass extinctions,ocean anoxic events and other environmental perturbations that mainly occurred in the ***,the results in previous studies clearly show that not all Hg enrichments are derived from volcanic inputs,which emphasize the need for more caution in using Hg as a fingerprint of *** a better understanding of Hg isotopes in the future,there will be important implications for Hg isotopes to reconstruct volcanic activities in the rock records and their impacts on biological evolution.

关键词： Mercury stable isotopes Large igneous province Mass extinction event Ocean anoxic event

A model for the mean velocity of debris flow movement based on the minimum energy dissipation principle

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Journal of Mountain Science 2024年第12期21卷 3961-3970页

作者： LI Xiangning CHEN Jiangang CHEN Xiaoqing ZHAO Wanyu CHEN Huayong ZHANG Shaoxiong Key laboratory of Mountain Hazards and earth surface process Institute of Mountain Hazards and EnvironmentChinese Academy of Sciences(CAS)Chengdu 610041China University of Chinese Academy Sciences Beijing 100049China Shijiazhuang Tiedao University Shijiazhuang 050043China

The geomorphic minimum energy dissipation principle is important in the development of gully evolutionary *** impact of debris flows on channels during movement also adheres to this theory.A minimum energy dissipation model for debris flows has been obtained from previous studies,which is derived from the flow rules of runoff along a channel under rainfall or ice-snow meltwater ***,the lack of consideration for erosion characteristics has hindered a comprehensive understanding of the movement characteristics of debris *** this paper,the phenomenon of volume increase resulting from the entrainment along debris flow movement is considered in order to derive a model for the mean velocity,reflecting the minimum energy dissipation *** entire expression of the mean velocity model is determined through 38 typical glacial and rainstorm debris flow *** evaluate the reliability of the proposed model,we employed 164 monitoring data from 1995 to 2000 in the Jiangjia gully,Yunnan,*** results show that the velocity calculated by the proposed model are highly correlated with those obtained from the monitoring ***,a comparison is made between the mean velocities calculated by the proposed model and those obtained from previous studies,highlighting the exceptional applicability of the proposed *** study will contribute to reveal the movement laws of debris flow along the channel.

关键词： Debris flow Minimum energy dissipation principle Longitudinal profile evolution Mean velocity

Prediction of Debris-flow Danger Area by Combining Hydrological and Inundation Simulation Methods

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Journal of Mountain Science 2011年第1期8卷 1-9页

作者： CUI Peng Key laboratory of Mountain Hazards and earth surface process Chinese Academy of Sciences Chengdu 610041 China Institute of Mountain Hazards and environment Chinese Academy of Sciences Chengdu 610041 China Graduate School of Chinese Academy of Sciences Beijing 100049 China

Debris flows have caused serious human casualties and economic losses in the regions strongly affected by the Ms8.0 Wenchuan earthquake of 2oo8. Debris flow mitigation and risk assessment is a key issue for reconstruction. The existing methods of inundation simulation are based on historical disasters and have no power of prediction. The rain- flood method can not yield detailed flow hydrograph and does not meet the need of inundation simulation. In this paper, the process of water flow was studied by using the Arc-SCS model combined with hydraulic method, and then the debris flow runoff process was calculated using the empirical formula combining the result from Arc-SCS. The peak discharge and runoff duration served as input of inundation simulation. Then, the dangerous area is predicted using kinematic wave method and Manning equation. Taking the debris flow in Huashiban gully in Beichuan County, Sichuan Province, China on 24 Sep. 2oo8 as example, the peak discharge of water flow and debris flow were calculated as 35.52 m3·s-1 and 215.66 m3·s-, with error of 4.15% compared to the measured values. The simulated area of debris-flow deposition was 161,500 m2, vs. the measured area of 144,097 m2, in error of 81.75%. The simulated maximum depth was 12.3 m, consistent with the real maximum depth between lO and 15 m according to the field survey. The minor error is mainly due to the flow impact on buildings and variations in cross-section configuration. The present methodology can be applied to predict debrisflow magnitude and evaluate its risk in other watersheds inthe earthquake area.

关键词： Debris flow Arc-SCS model Inundation simulation Risk analysis Wenchuan earthquake