In this paper, an analysis of adapted 20 extreme precipitation indices is calculated for a limited mountain area in southern Vietnam. The daily precipitation data from four stations in the period of more than 30 years...In this paper, an analysis of adapted 20 extreme precipitation indices is calculated for a limited mountain area in southern Vietnam. The daily precipitation data from four stations in the period of more than 30 years are selected. The statistical characteristics of maximum, minimum, mean, standard deviation, skewness, and kurtoris for each index are also analysed. A variety of distributions such as Normal, Lognormal, Beta, Gamma, Exponential, Loglogistic, and Johnson is used to find the best fit probability distribution for this area on the basic of the highest score. The scores are estimated based on the ranking of statistical goodness of fit test. The goodness of fit tests is the Anderson-Darling and Shapiro-Wilks tests. The best fit distribution for each index of extreme precipitation at each station is found out. Results revealed that the Johnson distribution is the best fit distribution to the data of very heavy precipitation days greater than 50 mm. Over a limited mountain area, it is difficult to fit a probability distribution to the precipitation fraction due to extremely wet days, number of extremely wet days, and number of extremely wet days when precipitation greater than 99 percentage. The lognormal, Johnson, and Loglogistic distribution are the best choices to fit most of the extreme precipitation indices over this area.展开更多
This paper evaluated the probability of landslide susceptibilities through the applica-tion of the Transient Rainfall Infiltration and Grid-Based Region Slope-Stability model in Cau river basin (Vietnam) using the sce...This paper evaluated the probability of landslide susceptibilities through the applica-tion of the Transient Rainfall Infiltration and Grid-Based Region Slope-Stability model in Cau river basin (Vietnam) using the scenarios-based approach under the influence of the warming climate. The tested cases were developed based on various options including rainfall amount and distribution, soil depth determination, and land-cover conditions. Input data for extreme rain events included historical rainstorm in 2013, the Probable Maximum Precipitation (PMP) with the durations of 24 hours and 48 hours. The results illustrated the reduction of slope stability when the land cover changed from land-use data in 2007 (Ha12) to land-use data in 2015 (Ha22). When the whole region was assumed to be replaced by soil (Ha02), the factor of safety (Fs) decreased to lower magnitude when compared to Fs value regarding to changes in land cover condition (Ha12 & Ha22) and changes in soil-depth (Ha33). The model simulations demonstrated the agreement with the slope-failure hazard association with the destabilizing factor such as slope-cutting activities at historical landslide events. Under the same land-cover and soil depth condition, the average value of factor of safety regarding to the historical rainstorm in 2013 (Ha32) declined by 0.069 and 0.189 when compared to Fs of the 24-hour PMP with the storm distribution type 3 (1332) and Fs of the 48-hour PMP with the storm distribution type 3 (2332), respectively. The results reveal that in a warming climate, changes in extreme precipitation in terms of rain-total, rain-duration, and rain-distribution would result in the expansion of slope instability in the hilly region. This application is considered as a prevailing method for landslide susceptibility analysis and would provide important information for authorities in developing adequate land-management in the river basin.展开更多
Landslide is common phenomena in construction field. Nowadays the cylindrical surface method has been used widely to analyze slope stability. However, this method contains two main disadvantages： firstly, the slip su...Landslide is common phenomena in construction field. Nowadays the cylindrical surface method has been used widely to analyze slope stability. However, this method contains two main disadvantages： firstly, the slip surface is assumed to be in circular shape while in fact it is ellipsoid commonly; and secondly, resolve by difference method causing immensely complicated process due to statically indeterminate equations. In this paper, the authors have presented a method that allows transferring of ellipsoid slip surface to cylindrical shape and carries out a single variable equation （by applying integration method）. Also thanks to this method, the current cylindrical surface method has been proved that its application is proper for man-made slopes but usually inappropriate for natural ones. Those results help analysis of slope stability reaching closer to reality.展开更多
文摘In this paper, an analysis of adapted 20 extreme precipitation indices is calculated for a limited mountain area in southern Vietnam. The daily precipitation data from four stations in the period of more than 30 years are selected. The statistical characteristics of maximum, minimum, mean, standard deviation, skewness, and kurtoris for each index are also analysed. A variety of distributions such as Normal, Lognormal, Beta, Gamma, Exponential, Loglogistic, and Johnson is used to find the best fit probability distribution for this area on the basic of the highest score. The scores are estimated based on the ranking of statistical goodness of fit test. The goodness of fit tests is the Anderson-Darling and Shapiro-Wilks tests. The best fit distribution for each index of extreme precipitation at each station is found out. Results revealed that the Johnson distribution is the best fit distribution to the data of very heavy precipitation days greater than 50 mm. Over a limited mountain area, it is difficult to fit a probability distribution to the precipitation fraction due to extremely wet days, number of extremely wet days, and number of extremely wet days when precipitation greater than 99 percentage. The lognormal, Johnson, and Loglogistic distribution are the best choices to fit most of the extreme precipitation indices over this area.
文摘This paper evaluated the probability of landslide susceptibilities through the applica-tion of the Transient Rainfall Infiltration and Grid-Based Region Slope-Stability model in Cau river basin (Vietnam) using the scenarios-based approach under the influence of the warming climate. The tested cases were developed based on various options including rainfall amount and distribution, soil depth determination, and land-cover conditions. Input data for extreme rain events included historical rainstorm in 2013, the Probable Maximum Precipitation (PMP) with the durations of 24 hours and 48 hours. The results illustrated the reduction of slope stability when the land cover changed from land-use data in 2007 (Ha12) to land-use data in 2015 (Ha22). When the whole region was assumed to be replaced by soil (Ha02), the factor of safety (Fs) decreased to lower magnitude when compared to Fs value regarding to changes in land cover condition (Ha12 & Ha22) and changes in soil-depth (Ha33). The model simulations demonstrated the agreement with the slope-failure hazard association with the destabilizing factor such as slope-cutting activities at historical landslide events. Under the same land-cover and soil depth condition, the average value of factor of safety regarding to the historical rainstorm in 2013 (Ha32) declined by 0.069 and 0.189 when compared to Fs of the 24-hour PMP with the storm distribution type 3 (1332) and Fs of the 48-hour PMP with the storm distribution type 3 (2332), respectively. The results reveal that in a warming climate, changes in extreme precipitation in terms of rain-total, rain-duration, and rain-distribution would result in the expansion of slope instability in the hilly region. This application is considered as a prevailing method for landslide susceptibility analysis and would provide important information for authorities in developing adequate land-management in the river basin.
文摘Landslide is common phenomena in construction field. Nowadays the cylindrical surface method has been used widely to analyze slope stability. However, this method contains two main disadvantages： firstly, the slip surface is assumed to be in circular shape while in fact it is ellipsoid commonly; and secondly, resolve by difference method causing immensely complicated process due to statically indeterminate equations. In this paper, the authors have presented a method that allows transferring of ellipsoid slip surface to cylindrical shape and carries out a single variable equation （by applying integration method）. Also thanks to this method, the current cylindrical surface method has been proved that its application is proper for man-made slopes but usually inappropriate for natural ones. Those results help analysis of slope stability reaching closer to reality.
