Road material constitutive model is the essential condition of pavement structure design,calculation,and maintenance decision.Experts have conducted in-depth studies on the problems and proposed many meaningful consti...Road material constitutive model is the essential condition of pavement structure design,calculation,and maintenance decision.Experts have conducted in-depth studies on the problems and proposed many meaningful constitutive models.However,these constitutive models have not been summarized and no uniform conclusion on the applicability of them is reported in the academic circle.The linear elastic model based on Hooke's law is still used in pavement structure design.This paper systematically reviewed the existing constitutive models that reflect the materials'mechanical properties and used for pavement structure calculation.These constitutive models were divided into three categories:linear,nonlinear,and damage models under repeated loads.The applicable conditions,parameter determination methods,advantages,and disadvantages of each model were introduced.Moreover,the model's feasibility in structural design and calculation was analyzed.Follow-up studies should focus on the parameter determination standard of viscoelastic constitutive models,the extension of the 1D constitutive model to 3D state,and the nonlinear constitutive models related to stress-strain state to drive the application of the constitutive models in pavement structure calculation and design.Furthermore,to evaluate the life cycle service performance of road materials and structures,establishing the pavement damage model from the structure perspective will be the future direction.展开更多
Landscape characters in estuarine regions generally controlled by tidal regimes and human activities like road construction.In this work,tidal channels and road construction in the Yellow River Delta(YRD)were extracte...Landscape characters in estuarine regions generally controlled by tidal regimes and human activities like road construction.In this work,tidal channels and road construction in the Yellow River Delta(YRD)were extracted by visual interpretation methods so as to decipher impacts of tidal channel development and road construction on landscape patch change during 1989–2016.Spatial distribution history of three wetlands,which covered by Phragmites australis(freshwater marsh,FM),Suaeda salsa(salt marsh,SM),and mudflats(MD)were also established.Results indicated that tidal channel,number,frequency,and fractal dimension were all the maximum in 2003,and the minimum in 1998,respectively.Road length,number,and density showed increasing trend during 1989–2016.MD were the predominant landscape type,followed by FM and SM during 1989-2016.Principal component analysis implied two extracted factors,F1 and F2,which could represent 91.93% of the total variations.F1 mainly proxied tidal channel development,while F2 represented road construction.A multiple linear regression analysis showed positive effects of both F1 and F2 on FM patch numbers and negative impacts on SM patch areaes with R^2 values of 0.416 and 0.599,respectively.Tidal channels were negatively related to MD patch numbers,while roads were positively related to that.In any case,road construction showed larger impacts on landscape type shifting than that of tidal channel development in the YRD.展开更多
After introducing the principle of float car data (FCD), this paper gives the primary flow of pre-handing and map- matching of the FCD. After analyzing the percentage of coverage of FCD on the road network, large quan...After introducing the principle of float car data (FCD), this paper gives the primary flow of pre-handing and map- matching of the FCD. After analyzing the percentage of coverage of FCD on the road network, large quantity of heritage database of routing status is used to estimate the routing velocity when lack of FCD on parts road segments. Multi liner regression model is then put forwarded by considering the spatial correlativity among the road network, and some model parameters are deduced when time series is classified in day and week. Besides, error of velocity probability and error of status probability are achieved based on the result from field testing while the feasibility and reliability of the velocity estimation model is obtained as well. Finally, as a case study in Shanghai center area, the whole routing velocity in the road network is estimated and published in real time.展开更多
基金funded by the National Key of Research and Development Plan under grant no.2020YFA0714300.
文摘Road material constitutive model is the essential condition of pavement structure design,calculation,and maintenance decision.Experts have conducted in-depth studies on the problems and proposed many meaningful constitutive models.However,these constitutive models have not been summarized and no uniform conclusion on the applicability of them is reported in the academic circle.The linear elastic model based on Hooke's law is still used in pavement structure design.This paper systematically reviewed the existing constitutive models that reflect the materials'mechanical properties and used for pavement structure calculation.These constitutive models were divided into three categories:linear,nonlinear,and damage models under repeated loads.The applicable conditions,parameter determination methods,advantages,and disadvantages of each model were introduced.Moreover,the model's feasibility in structural design and calculation was analyzed.Follow-up studies should focus on the parameter determination standard of viscoelastic constitutive models,the extension of the 1D constitutive model to 3D state,and the nonlinear constitutive models related to stress-strain state to drive the application of the constitutive models in pavement structure calculation and design.Furthermore,to evaluate the life cycle service performance of road materials and structures,establishing the pavement damage model from the structure perspective will be the future direction.
基金Under the auspices of National Key Research and Development Project(No.2017YFC0505901)
文摘Landscape characters in estuarine regions generally controlled by tidal regimes and human activities like road construction.In this work,tidal channels and road construction in the Yellow River Delta(YRD)were extracted by visual interpretation methods so as to decipher impacts of tidal channel development and road construction on landscape patch change during 1989–2016.Spatial distribution history of three wetlands,which covered by Phragmites australis(freshwater marsh,FM),Suaeda salsa(salt marsh,SM),and mudflats(MD)were also established.Results indicated that tidal channel,number,frequency,and fractal dimension were all the maximum in 2003,and the minimum in 1998,respectively.Road length,number,and density showed increasing trend during 1989–2016.MD were the predominant landscape type,followed by FM and SM during 1989-2016.Principal component analysis implied two extracted factors,F1 and F2,which could represent 91.93% of the total variations.F1 mainly proxied tidal channel development,while F2 represented road construction.A multiple linear regression analysis showed positive effects of both F1 and F2 on FM patch numbers and negative impacts on SM patch areaes with R^2 values of 0.416 and 0.599,respectively.Tidal channels were negatively related to MD patch numbers,while roads were positively related to that.In any case,road construction showed larger impacts on landscape type shifting than that of tidal channel development in the YRD.
文摘After introducing the principle of float car data (FCD), this paper gives the primary flow of pre-handing and map- matching of the FCD. After analyzing the percentage of coverage of FCD on the road network, large quantity of heritage database of routing status is used to estimate the routing velocity when lack of FCD on parts road segments. Multi liner regression model is then put forwarded by considering the spatial correlativity among the road network, and some model parameters are deduced when time series is classified in day and week. Besides, error of velocity probability and error of status probability are achieved based on the result from field testing while the feasibility and reliability of the velocity estimation model is obtained as well. Finally, as a case study in Shanghai center area, the whole routing velocity in the road network is estimated and published in real time.
