随着环境保护意识的提高,采用植被对路基工程进行护坡的措施受到广泛关注。我国生态护坡理论研究主要集中在生态效益这一方面,理论远远落后于防护技术应用的发展。采用科学软件CHASM(Combined hydrology and stability model)研究考虑...随着环境保护意识的提高,采用植被对路基工程进行护坡的措施受到广泛关注。我国生态护坡理论研究主要集中在生态效益这一方面,理论远远落后于防护技术应用的发展。采用科学软件CHASM(Combined hydrology and stability model)研究考虑降雨影响的生态护坡工程的工作机理,并确定路基植被边坡的主要安全技术指标。填土内摩擦角φ为30°,宜选取小于35°的边坡角,植被对边坡稳定性影响是有限的。植被使不同强度的填土边坡安全系数提高10%～12%。高渗透性路基,坡面种植树木的边坡安全系数比坡脚种植的高,移除坡脚的植被相对安全;低渗透性路基,植被对边坡安全产生负效应。降雨强度不同,植被对安全系数的影响也不同,当降雨作用没有超过植被的调节能力时,边坡安全系数基本在提高;反之,边坡安全系数会出现明显的下降。展开更多
Most previous land-surface model calibration studies have defined globalranges for their parameters to search for optimal parameter sets. Little work has been conducted tostudy the impacts of realistic versus global r...Most previous land-surface model calibration studies have defined globalranges for their parameters to search for optimal parameter sets. Little work has been conducted tostudy the impacts of realistic versus global ranges as well as model complexities on the calibrationand uncertainty estimates. The primary purpose of this paper is to investigate these impacts byemploying Bayesian Stochastic Inversion (BSI) to the Chameleon Surface Model (CHASM). The CHASM wasdesigned to explore the general aspects of land-surface energy balance representation within acommon modeling framework that can be run from a simple energy balance formulation to a complexmosaic type structure. The BSI is an uncertainty estimation technique based on Bayes theorem,importance sampling, and very fast simulated annealing. The model forcing data and surface flux datawere collected at seven sites representing a wide range of climate and vegetation conditions. Foreach site, four experiments were performed with simple and complex CHASM formulations as well asrealistic and global parameter ranges. Twenty eight experiments were conducted and 50 000 parametersets were used for each run. The results show that the use of global and realistic ranges givessimilar simulations for both modes for most sites, but the global ranges tend to produce someunreasonable optimal parameter values. Comparison of simple and complex modes shows that the simplemode has more parameters with unreasonable optimal values. Use of parameter ranges and modelcomplexities have significant impacts on frequency distribution of parameters, marginal posteriorprobability density functions, and estimates of uncertainty of simulated sensible and latent heatfluxes. Comparison between model complexity and parameter ranges shows that the former has moresignificant impacts on parameter and uncertainty estimations.展开更多
The Wuhan Yangtze River Bridge was one of the 156 projects China built with support from the Soviet Union during the 1950s. In June 1956,Chairman Mao Zedong wrote a poem of praise:'A bridge will fly to span the no...The Wuhan Yangtze River Bridge was one of the 156 projects China built with support from the Soviet Union during the 1950s. In June 1956,Chairman Mao Zedong wrote a poem of praise:'A bridge will fly to span the north and south, turning a deep chasm into a thoroughfare'.展开更多
文摘随着环境保护意识的提高,采用植被对路基工程进行护坡的措施受到广泛关注。我国生态护坡理论研究主要集中在生态效益这一方面,理论远远落后于防护技术应用的发展。采用科学软件CHASM(Combined hydrology and stability model)研究考虑降雨影响的生态护坡工程的工作机理,并确定路基植被边坡的主要安全技术指标。填土内摩擦角φ为30°,宜选取小于35°的边坡角,植被对边坡稳定性影响是有限的。植被使不同强度的填土边坡安全系数提高10%～12%。高渗透性路基,坡面种植树木的边坡安全系数比坡脚种植的高,移除坡脚的植被相对安全;低渗透性路基,植被对边坡安全产生负效应。降雨强度不同,植被对安全系数的影响也不同,当降雨作用没有超过植被的调节能力时,边坡安全系数基本在提高;反之,边坡安全系数会出现明显的下降。
文摘Most previous land-surface model calibration studies have defined globalranges for their parameters to search for optimal parameter sets. Little work has been conducted tostudy the impacts of realistic versus global ranges as well as model complexities on the calibrationand uncertainty estimates. The primary purpose of this paper is to investigate these impacts byemploying Bayesian Stochastic Inversion (BSI) to the Chameleon Surface Model (CHASM). The CHASM wasdesigned to explore the general aspects of land-surface energy balance representation within acommon modeling framework that can be run from a simple energy balance formulation to a complexmosaic type structure. The BSI is an uncertainty estimation technique based on Bayes theorem,importance sampling, and very fast simulated annealing. The model forcing data and surface flux datawere collected at seven sites representing a wide range of climate and vegetation conditions. Foreach site, four experiments were performed with simple and complex CHASM formulations as well asrealistic and global parameter ranges. Twenty eight experiments were conducted and 50 000 parametersets were used for each run. The results show that the use of global and realistic ranges givessimilar simulations for both modes for most sites, but the global ranges tend to produce someunreasonable optimal parameter values. Comparison of simple and complex modes shows that the simplemode has more parameters with unreasonable optimal values. Use of parameter ranges and modelcomplexities have significant impacts on frequency distribution of parameters, marginal posteriorprobability density functions, and estimates of uncertainty of simulated sensible and latent heatfluxes. Comparison between model complexity and parameter ranges shows that the former has moresignificant impacts on parameter and uncertainty estimations.
文摘The Wuhan Yangtze River Bridge was one of the 156 projects China built with support from the Soviet Union during the 1950s. In June 1956,Chairman Mao Zedong wrote a poem of praise:'A bridge will fly to span the north and south, turning a deep chasm into a thoroughfare'.
