SiB2(Simple Biosphere Model version 2)是将植物生理学、土壤微气象学结合起来用以研究单层植被中的水、能量以及CO_2通量变化的陆面过程模型。为了使SiB2适用于江西低丘红壤区农田小流域生态系统,根据在余江县花生地试验区的实地测...SiB2(Simple Biosphere Model version 2)是将植物生理学、土壤微气象学结合起来用以研究单层植被中的水、能量以及CO_2通量变化的陆面过程模型。为了使SiB2适用于江西低丘红壤区农田小流域生态系统,根据在余江县花生地试验区的实地测量以及SiB2提供的土壤和作物分类,确定土壤特性参数和花生形态学参数,调整部分花生生理学、光学参数,并修正SiB2长波辐射的计算。在此基础上,选取花生幼苗、开花和饱果成熟三个关键的生长期的近地层观测资料代入模式,对花生根域土壤水分动态变化进行短期模拟,探究不同生长期的花生生长特性和气象因素对模拟结果的影响,并且针对模型提出了基于集合卡尔曼滤波的单点数据同化方案以提高精度。与观测结果进行验证后,结果表明:在不同生长期下,极端天气越少、植株形态越成熟稳定,模拟结果越准确。在进行数据同化后,模型精度得到明显提高。展开更多
Rainfall, as one of the most significant factors triggering the residual soil slope failure, leads to not only the reduction of soil shear strength, but also the increase of soil weight and the decrease of matric suct...Rainfall, as one of the most significant factors triggering the residual soil slope failure, leads to not only the reduction of soil shear strength, but also the increase of soil weight and the decrease of matric suction as well. All these modifications in soil properties have important influence on the slope stability. The water infiltration and redistribution inside the slope are the preconditions of the slope stability under rainfall conditions. Based on the numerical simulation via finite element method, the water infiltration process under rainfall conditions was studied in the present work. The emphases are the formation, distribution and dissipation of transient saturated zone. As for the calculation parameters, the SWCC and the saturated permeability have been determined by pressure plate test and variable head test respectively. The entire process(formation, development, dissipation) of the transient saturated zone was studied in detail. The variations of volumetric water content, matric suction and hydraulic gradient inside the slope, and the eventually raise of groundwater table were characterized and discussed, too. The results show that the major cause of the formation of transient saturated zone is ascribed to the fact that the exudation velocity of rainwater on the wetting front is less than the infiltration velocity of rainfall; as a result, the water content of the soil increases. On the other hand, the formation and extension of transient saturated zone have a close relationship with rainfall intensity and duration. The results can help the geotechnical engineers for the deeper understanding of the failure of residual slope under rainfall condition. It is also suggested that the proper drainage system in the slope may be the cost-effective slope failure mitigation method.展开更多
文摘SiB2(Simple Biosphere Model version 2)是将植物生理学、土壤微气象学结合起来用以研究单层植被中的水、能量以及CO_2通量变化的陆面过程模型。为了使SiB2适用于江西低丘红壤区农田小流域生态系统,根据在余江县花生地试验区的实地测量以及SiB2提供的土壤和作物分类,确定土壤特性参数和花生形态学参数,调整部分花生生理学、光学参数,并修正SiB2长波辐射的计算。在此基础上,选取花生幼苗、开花和饱果成熟三个关键的生长期的近地层观测资料代入模式,对花生根域土壤水分动态变化进行短期模拟,探究不同生长期的花生生长特性和气象因素对模拟结果的影响,并且针对模型提出了基于集合卡尔曼滤波的单点数据同化方案以提高精度。与观测结果进行验证后,结果表明:在不同生长期下,极端天气越少、植株形态越成熟稳定,模拟结果越准确。在进行数据同化后,模型精度得到明显提高。
基金Projects(51508040,51578079,51678074,51678073)supported by the National Natural Science Foundation of ChinaProject(KFJ160601)supported by the Open Fund of Engineering Laboratory of Spatial Information Technology of Highway Geological Disaster Early Warning in Hunan Province(Changsha University of Science and Technology),China
文摘Rainfall, as one of the most significant factors triggering the residual soil slope failure, leads to not only the reduction of soil shear strength, but also the increase of soil weight and the decrease of matric suction as well. All these modifications in soil properties have important influence on the slope stability. The water infiltration and redistribution inside the slope are the preconditions of the slope stability under rainfall conditions. Based on the numerical simulation via finite element method, the water infiltration process under rainfall conditions was studied in the present work. The emphases are the formation, distribution and dissipation of transient saturated zone. As for the calculation parameters, the SWCC and the saturated permeability have been determined by pressure plate test and variable head test respectively. The entire process(formation, development, dissipation) of the transient saturated zone was studied in detail. The variations of volumetric water content, matric suction and hydraulic gradient inside the slope, and the eventually raise of groundwater table were characterized and discussed, too. The results show that the major cause of the formation of transient saturated zone is ascribed to the fact that the exudation velocity of rainwater on the wetting front is less than the infiltration velocity of rainfall; as a result, the water content of the soil increases. On the other hand, the formation and extension of transient saturated zone have a close relationship with rainfall intensity and duration. The results can help the geotechnical engineers for the deeper understanding of the failure of residual slope under rainfall condition. It is also suggested that the proper drainage system in the slope may be the cost-effective slope failure mitigation method.
