为探究当前及未来土地利用下的渭河流域水文响应特征,支撑流域水资源可持续发展,采用元胞自动机-马尔可夫(cellular automata Markov,CA-Markov)模型预测2030年的土地利用类型,基于1985年、2000年、2015年和预测的2030年的土地利用数据...为探究当前及未来土地利用下的渭河流域水文响应特征,支撑流域水资源可持续发展,采用元胞自动机-马尔可夫(cellular automata Markov,CA-Markov)模型预测2030年的土地利用类型,基于1985年、2000年、2015年和预测的2030年的土地利用数据构建相应的土地利用与水文过程模拟模型(soil and water assessment tool+,SWAT+)。模型检验显示E_(NS)和R^(2)均大于0.7且P_(BIAS)绝对值小于20%。结果表明:1985-2030年丰水年径流系数呈V形变化,并与耕地面积负相关,而在平水年、枯水年呈波动下降的变化趋势,2030年相比2015年平水年、枯水年径流系数分别下降3.1%和5.7%。同时,不同子流域水文过程存在差异性,2030年相比2015年,流域产流量在西部山地丘陵地区随林地面积增加有所减少,而东部关中平原地区则随城市用地面积的增加有所上升。整体而言,2030年渭河流域对水资源的需求随着土地利用的变化不断增加,枯水年水资源压力会进一步加大。展开更多
The study results of the internal friction character of geomaterials conclude that the internal friction exists in mechanical elements all the time having a direction opposite to the shear stress,and the deformation f...The study results of the internal friction character of geomaterials conclude that the internal friction exists in mechanical elements all the time having a direction opposite to the shear stress,and the deformation failure mechanism of geomaterials greatly differs from that of metals. For metals,the failure results from shear stresses make the crystal structure slip; whereas for geomaterials,owing to its attribute of granular structures,their deformation follows the friction law,it is the co-action of shear stresses and perpendicular stresses that makes grains overcome the frictions between them,thus leading to the final failure of relative sliding.Therefore,on the basis of the cognition above,a triple shear energy criterion is proposed. Its corresponding Drucker-Prager criterion for geomaterials is also given. The new criterion can be rewritten to the Mohr-Coulomb criterion by neglecting the effect of the intermediate principal stress,and to the Mises criterion by not taking the internal friction angle into consideration. Then the studies of yield criteria commonly used are conducted systematically from the points of stress,strain and energy of geomaterials. The results show that no matter which expression form of stress,strain or energy is used for the yield criterion,the essence is the same and the triple shear energy yield criterion is the unified criterion of materials. Finally,the experimental verification is conducted in connection with the practical application of the triple shear energy yield criterion in an engineering project,and the calculation result shows that the Mohr-Coulomb criterion which only takes the single shear surface into account is more conservative than the energy criterion that does consider the effect of triple shear surfaces.展开更多
文摘为探究当前及未来土地利用下的渭河流域水文响应特征,支撑流域水资源可持续发展,采用元胞自动机-马尔可夫(cellular automata Markov,CA-Markov)模型预测2030年的土地利用类型,基于1985年、2000年、2015年和预测的2030年的土地利用数据构建相应的土地利用与水文过程模拟模型(soil and water assessment tool+,SWAT+)。模型检验显示E_(NS)和R^(2)均大于0.7且P_(BIAS)绝对值小于20%。结果表明:1985-2030年丰水年径流系数呈V形变化,并与耕地面积负相关,而在平水年、枯水年呈波动下降的变化趋势,2030年相比2015年平水年、枯水年径流系数分别下降3.1%和5.7%。同时,不同子流域水文过程存在差异性,2030年相比2015年,流域产流量在西部山地丘陵地区随林地面积增加有所减少,而东部关中平原地区则随城市用地面积的增加有所上升。整体而言,2030年渭河流域对水资源的需求随着土地利用的变化不断增加,枯水年水资源压力会进一步加大。
基金National Natural Science Foundation of China (No.50609027)
文摘The study results of the internal friction character of geomaterials conclude that the internal friction exists in mechanical elements all the time having a direction opposite to the shear stress,and the deformation failure mechanism of geomaterials greatly differs from that of metals. For metals,the failure results from shear stresses make the crystal structure slip; whereas for geomaterials,owing to its attribute of granular structures,their deformation follows the friction law,it is the co-action of shear stresses and perpendicular stresses that makes grains overcome the frictions between them,thus leading to the final failure of relative sliding.Therefore,on the basis of the cognition above,a triple shear energy criterion is proposed. Its corresponding Drucker-Prager criterion for geomaterials is also given. The new criterion can be rewritten to the Mohr-Coulomb criterion by neglecting the effect of the intermediate principal stress,and to the Mises criterion by not taking the internal friction angle into consideration. Then the studies of yield criteria commonly used are conducted systematically from the points of stress,strain and energy of geomaterials. The results show that no matter which expression form of stress,strain or energy is used for the yield criterion,the essence is the same and the triple shear energy yield criterion is the unified criterion of materials. Finally,the experimental verification is conducted in connection with the practical application of the triple shear energy yield criterion in an engineering project,and the calculation result shows that the Mohr-Coulomb criterion which only takes the single shear surface into account is more conservative than the energy criterion that does consider the effect of triple shear surfaces.
