Located in the eastern margin of the Tibetan Plateau,the Gonghe-Yushu high-grade highway was the first of its kind in plateau permafrost regions.Most of the road sections along the high-grade highway are unstable or e...Located in the eastern margin of the Tibetan Plateau,the Gonghe-Yushu high-grade highway was the first of its kind in plateau permafrost regions.Most of the road sections along the high-grade highway are unstable or extremely unstable warm permafrost with an average annual ground temperature above −1℃,which is vulnerable to global warming and human engineering activities.This paper describes permafrost characteristics,roadbed design,and operation of the Gonghe-Yushu high-grade highway in detail.It is found that thaw settlement of warm and ice-rich permafrost is the main cause of subgrade subsidence in permafrost sections of this highway due to insufficient permafrost survey and drainage design.It is recommended that the interception and drainage system's design be optimized,and the permafrost upper limit and the variation of ground temperature be further investigated to provide essential data for the treatment of highway distress.It should be emphasized that protecting permafrost soil environment and optimized engineering design are crucial to successful high-grade highway engineering in permafrost regions.展开更多
The research shows that the selection of pavement type is very important for the thermal stability of high-grade highway embankment in permafrost regions because of the different solar absorption rates between asphalt...The research shows that the selection of pavement type is very important for the thermal stability of high-grade highway embankment in permafrost regions because of the different solar absorption rates between asphalt concrete and asphalt concrete pavement.In this paper,the common embankment of high-grade highway in permafrost regions is selected as the research object to study the influence of asphalt concrete and cement concrete pavement on the embankment temperature,freeze-thaw cycle process and the change law of the permafrost table,which provides a basis for the use of reasonable pavement materials in permafrost regions.展开更多
Limestone fines are increasingly used in cement and concrete for improved material properties and sustainability. This paper presents recent research at Iowa State University on utilization of limestone fines in concr...Limestone fines are increasingly used in cement and concrete for improved material properties and sustainability. This paper presents recent research at Iowa State University on utilization of limestone fines in concrete. It includes the beneficial uses of limestone fines in： （1） limestone blended Portland cement; （2） SFSCC （semi-flowable self-consolidating concrete）; and （3） HPC （high performance concrete）. The research results show that using 5%-10% of limestone fines to replace for Type IP cement （with 25% fly ash） increased mortar strength. Well-designed SFSCC with 25% limestone fines （by mass of cementitious materials） displayed desirable rheological and mechanical properties required for slip-forming construction. The newly developed limestone fines-based HPC reached the one-day compressive strength of over 28 MPa.展开更多
This paper develops a social media-disaster resilience analysis framework by categorizing types of social media use and their challenges to better understand and assess its role in disaster resilience research and man...This paper develops a social media-disaster resilience analysis framework by categorizing types of social media use and their challenges to better understand and assess its role in disaster resilience research and management.The framework is derived primarily from several case studies of Twitter use in three hurricane events in the United States-Hurricanes Isaac,Sandy,and Harvey.The paper first outlines four major contributions of social media data for disaster resilience research and management,which include serving as an effective communication platform,providing ground truth information for emergency response and rescue operations,providing information on people's sentiments,and allowing predictive modeling.However,there are four_key challenges to its uses,which include,easy spreading of false information,social and geographical disparities of Twitter use,technical issues on processing and analyzing big and noisy data,especially on improving the locational accuracy of the tweets,and algorithm bias in Al and other types of modeling.Then,the paper proposes twenty strategies that the four sectors of the social media community-organizations,individuals,social media companies,and researchers-could take to improve social media use to increase disaster resilience.展开更多
Twitter can supply useful information on infrastructure impacts to the emergency managers during major disasters,but it is time consuming to filter through many irrelevant tweets.Previous studies have identified the t...Twitter can supply useful information on infrastructure impacts to the emergency managers during major disasters,but it is time consuming to filter through many irrelevant tweets.Previous studies have identified the types of messages that can be found on social media during disasters,but few solutions have been proposed to efficiently extract useful ones.We present a framework that can be applied in a timely manner to provide disaster impact information sourced from social media.The framework is tested on a well-studied and data-rich case of Hurricane Harvey.The procedures consist of filtering the raw Twitter data based on keywords,location,and tweet attributes,and then applying the latent Dirichlet allocation(LDA) to separate the tweets from the disaster affected area into categories(topics) useful to emergency managers.The LDA revealed that out of 24 topics found in the data,nine were directly related to disaster impacts-for example,outages,closures,flooded roads,and damaged infrastructure.Features such as frequent hashtags,mentions,URLs,and useful images were then extracted and analyzed.The relevant tweets,along with useful images,were correlated at the county level with flood depth,distributed disaster aid(damage),and population density.Significant correlations were found between the nine relevant topics and population density but not flood depth and damage,suggesting that more research into the suitability of social media data for disaster impacts modeling is needed.The results from this study provide baseline information for such efforts in the future.展开更多
Despite the increasingly prominent role of social media in disaster events,studies analyzing its use in rescue operations remain scanty.Hurricane Harvey hit Texas with unprecedented rainfall and flooding in 2017 and w...Despite the increasingly prominent role of social media in disaster events,studies analyzing its use in rescue operations remain scanty.Hurricane Harvey hit Texas with unprecedented rainfall and flooding in 2017 and was marked by widespread use of social media for rescue requests.We conducted a survey of 195 Twitter users in Houston and surrounding communities who had requested for rescue during Harvey.The objective was to investigate our targeted group’s socioeconomic and flood exposure characteristics,report the effectiveness of Twitter,and highlight lessons learnt and suggestions made for its use in future rescue missions.Survey revealed that those requesting rescue on Twitter were better educated,employed(80%),and homeowners(81%).Majority of them were flooded(87%),but remained satisfied with current location and did not consider moving.Calling relatives and friends for rescue was most responsive and yielded higher assistance-provided rate than using Twitter.Our respondents found Twitter helpful,but identified issues such as not knowing when volunteers received their requests or whether they would send help.They suggested promoting Twitter accounts and hashtags that accept emergency requests.This study provides baseline information and actionable suggestions for first responders,community managers,and resilience practitioners to improve future rescue missions.展开更多
Self-consolidating concrete(SCC)with manufactured sand(MSCC)is crucial to guarantee the quality of concrete construction technology and the associated property.The properties of MSCC with different microlimestone powd...Self-consolidating concrete(SCC)with manufactured sand(MSCC)is crucial to guarantee the quality of concrete construction technology and the associated property.The properties of MSCC with different microlimestone powder(MLS)replacements of retreated manufactured sand(TMsand)are investigated in this study.The result indicates that high-performance SCC,made using TMsand(TMSCC),achieved high workability,good mechanical properties,and durability by optimizing MLS content and adding fy ash and silica fume.In particular,the TMSCC with 12%MLS content exhibits the best workability,and the TMSCC with 4%MLS content has the highest strength in the late age,which is even better than that of SCC made with the river sand(R sand).Though MLS content slightly affects the hydration reaction of cement and mainly plays a role in the nucleation process in concrete structures compared to silica fume and fly ash,increasing MLS content can evidently have a significant impact on the early age hydration progress.TMsand with MLS content ranging from 8%to 12%may be a suitable alternative for the Rsand used in the SCC as fine aggregate.The obtained results can be used to promote the application of SCC made with manufactured sand and mineral admixtures for concrete-based infrastructure.展开更多
基金supported by the National Natural Science Foundation of China(Nos.41801046,42161026)the Natural Science Foundation of Qinghai Province(No.2021-ZJ-716)the Transportation Science and Technology Project of Qinghai Province(No.2019-06&No.2018-02).
文摘Located in the eastern margin of the Tibetan Plateau,the Gonghe-Yushu high-grade highway was the first of its kind in plateau permafrost regions.Most of the road sections along the high-grade highway are unstable or extremely unstable warm permafrost with an average annual ground temperature above −1℃,which is vulnerable to global warming and human engineering activities.This paper describes permafrost characteristics,roadbed design,and operation of the Gonghe-Yushu high-grade highway in detail.It is found that thaw settlement of warm and ice-rich permafrost is the main cause of subgrade subsidence in permafrost sections of this highway due to insufficient permafrost survey and drainage design.It is recommended that the interception and drainage system's design be optimized,and the permafrost upper limit and the variation of ground temperature be further investigated to provide essential data for the treatment of highway distress.It should be emphasized that protecting permafrost soil environment and optimized engineering design are crucial to successful high-grade highway engineering in permafrost regions.
基金supported by the National Natural Science Foundation of China(Nots.41801046,42161026)the Natural Science Foundation of Qinghai Province(No.2021-ZJ-716)the Transportation Science and Technology Project of Qinghai Province(No.2019-06&No.2018-02).
文摘The research shows that the selection of pavement type is very important for the thermal stability of high-grade highway embankment in permafrost regions because of the different solar absorption rates between asphalt concrete and asphalt concrete pavement.In this paper,the common embankment of high-grade highway in permafrost regions is selected as the research object to study the influence of asphalt concrete and cement concrete pavement on the embankment temperature,freeze-thaw cycle process and the change law of the permafrost table,which provides a basis for the use of reasonable pavement materials in permafrost regions.
文摘Limestone fines are increasingly used in cement and concrete for improved material properties and sustainability. This paper presents recent research at Iowa State University on utilization of limestone fines in concrete. It includes the beneficial uses of limestone fines in： （1） limestone blended Portland cement; （2） SFSCC （semi-flowable self-consolidating concrete）; and （3） HPC （high performance concrete）. The research results show that using 5%-10% of limestone fines to replace for Type IP cement （with 25% fly ash） increased mortar strength. Well-designed SFSCC with 25% limestone fines （by mass of cementitious materials） displayed desirable rheological and mechanical properties required for slip-forming construction. The newly developed limestone fines-based HPC reached the one-day compressive strength of over 28 MPa.
基金supported by U.S.National Science Foundation:[Grant Number Award#:1762600 and 1620451].
文摘This paper develops a social media-disaster resilience analysis framework by categorizing types of social media use and their challenges to better understand and assess its role in disaster resilience research and management.The framework is derived primarily from several case studies of Twitter use in three hurricane events in the United States-Hurricanes Isaac,Sandy,and Harvey.The paper first outlines four major contributions of social media data for disaster resilience research and management,which include serving as an effective communication platform,providing ground truth information for emergency response and rescue operations,providing information on people's sentiments,and allowing predictive modeling.However,there are four_key challenges to its uses,which include,easy spreading of false information,social and geographical disparities of Twitter use,technical issues on processing and analyzing big and noisy data,especially on improving the locational accuracy of the tweets,and algorithm bias in Al and other types of modeling.Then,the paper proposes twenty strategies that the four sectors of the social media community-organizations,individuals,social media companies,and researchers-could take to improve social media use to increase disaster resilience.
基金This article is based on work supported by two grants from the National Science Foundation of the United States(under Grant Numbers 1620451 and 1945787).Any opinions,fndings,and conclusions or recommendations expressed in this article are those of the authors and do not necessarily refect the views of the National Science Foundation.
文摘Twitter can supply useful information on infrastructure impacts to the emergency managers during major disasters,but it is time consuming to filter through many irrelevant tweets.Previous studies have identified the types of messages that can be found on social media during disasters,but few solutions have been proposed to efficiently extract useful ones.We present a framework that can be applied in a timely manner to provide disaster impact information sourced from social media.The framework is tested on a well-studied and data-rich case of Hurricane Harvey.The procedures consist of filtering the raw Twitter data based on keywords,location,and tweet attributes,and then applying the latent Dirichlet allocation(LDA) to separate the tweets from the disaster affected area into categories(topics) useful to emergency managers.The LDA revealed that out of 24 topics found in the data,nine were directly related to disaster impacts-for example,outages,closures,flooded roads,and damaged infrastructure.Features such as frequent hashtags,mentions,URLs,and useful images were then extracted and analyzed.The relevant tweets,along with useful images,were correlated at the county level with flood depth,distributed disaster aid(damage),and population density.Significant correlations were found between the nine relevant topics and population density but not flood depth and damage,suggesting that more research into the suitability of social media data for disaster impacts modeling is needed.The results from this study provide baseline information for such efforts in the future.
基金supported by two research grants from the the U.S.National Science Foundation(NSF)Social and Economic Sciences Division(SES)Hurricane Harvey 2017 Program(Award No.1762600)the NSF Interdisciplinary Behavioral and Social Science Research(IBSS)Program(Award No.1620451).
文摘Despite the increasingly prominent role of social media in disaster events,studies analyzing its use in rescue operations remain scanty.Hurricane Harvey hit Texas with unprecedented rainfall and flooding in 2017 and was marked by widespread use of social media for rescue requests.We conducted a survey of 195 Twitter users in Houston and surrounding communities who had requested for rescue during Harvey.The objective was to investigate our targeted group’s socioeconomic and flood exposure characteristics,report the effectiveness of Twitter,and highlight lessons learnt and suggestions made for its use in future rescue missions.Survey revealed that those requesting rescue on Twitter were better educated,employed(80%),and homeowners(81%).Majority of them were flooded(87%),but remained satisfied with current location and did not consider moving.Calling relatives and friends for rescue was most responsive and yielded higher assistance-provided rate than using Twitter.Our respondents found Twitter helpful,but identified issues such as not knowing when volunteers received their requests or whether they would send help.They suggested promoting Twitter accounts and hashtags that accept emergency requests.This study provides baseline information and actionable suggestions for first responders,community managers,and resilience practitioners to improve future rescue missions.
基金All the authors appreciate the supports from the Australian Research Council(DEI50101751,IH150100006)University of Technology Sydney Research Academic Program at Tech Lab(UTS RAPT),University of Technology Sydney Tech Lab Blue Sky Research Scheme.
文摘Self-consolidating concrete(SCC)with manufactured sand(MSCC)is crucial to guarantee the quality of concrete construction technology and the associated property.The properties of MSCC with different microlimestone powder(MLS)replacements of retreated manufactured sand(TMsand)are investigated in this study.The result indicates that high-performance SCC,made using TMsand(TMSCC),achieved high workability,good mechanical properties,and durability by optimizing MLS content and adding fy ash and silica fume.In particular,the TMSCC with 12%MLS content exhibits the best workability,and the TMSCC with 4%MLS content has the highest strength in the late age,which is even better than that of SCC made with the river sand(R sand).Though MLS content slightly affects the hydration reaction of cement and mainly plays a role in the nucleation process in concrete structures compared to silica fume and fly ash,increasing MLS content can evidently have a significant impact on the early age hydration progress.TMsand with MLS content ranging from 8%to 12%may be a suitable alternative for the Rsand used in the SCC as fine aggregate.The obtained results can be used to promote the application of SCC made with manufactured sand and mineral admixtures for concrete-based infrastructure.
