This study presents a procedure for calculating the change of the safety factor for unsaturated slopes of homogenous, residual soils suffering from rainfall infiltration within Khanh Vinh district, Khanh Hòa province. Rainfall is supposed as a main trigger caused failure of the potential sliding slopes. Rainwater into the slope due to infiltration caused an increase in moisture content and negative pore water pressure; a decrease in matric suction and in shear strength on the failure surface. Thus, slopes are reduced stability and can be failed. Soil permeability and rainfall intensity were found to be the primary factors controlling the instability of slopes due to rainfall, while the initial water table location and slope geometry only played a secondary role. A numerical model of analysis coupled seepage-stability used to simulate the seepage and slope stability under conditions of specific environment such as soil permeability, rainfall intensity, water table location and slope geometry in the study area. The relationships between safety factor and rainfall intensity, soil permeability, angle slope, high slope were identified to provide a good indication for the management of landslide hazards under the effects of rainfall.
In this paper, a Monte Carlo simulation used to analyze probabilistic slope stability. The results including: probabilistic slope failure and reliability index with respect to factor of safety under the effects of uncertainties in the parameters of soil properties. Base on this informations, geotechnical engineers how to get optimal designs to prevent slope failure. In addition, the purpose of this paper is to show that standard deviation of soil properties can be applied in simple ways, without more data, time, or effort than are commonly available in geotechnical engineering practice. Applying Monte Carlo simulation to evaluate probabilistic slope stability on route Nha Trang - Da Lat.
The purpose of this study is to produce landslide hazard map in Khanh Vinh district, Khanh Hoa province using logistic regression method integrated with GIS analytical tools. The spatial relationship between landslide-related factors such as topography; lithology; vegetation; maximum precipitation in year; distance from roads; distance from drainages; distance from faults and the distribution of landslides were used in the landslide hazard analyses. Using success rate and prediction rate curve assess the fit and accuracy of logistic regression method. The results show that this method have the goodness of fit and the high accuracy (Areas Under Curves - AUC = 0.8 ~ 0.9). Bayesian Model Average (BMA) of the R statistical software was applied to identify the most influential factors and the combinatorial optimization models of landslide-related factors. There are four the most important landslide-related factors and five combinatorial optimization models of landslide-related factors. Model 3 (slope angle, slope aspect, altitude, distance from roads and maximum precipitation in year) is the best optimization.
A mathematical model was used by the authors (software developed by Dr. F28 Le Song Giang) to study the change of the salt boundary river systems Saigon - Dong Nai under the effect of sea level rise in the different cases for Ho Chi Minh City, taking into account the change of amplitude and phase shift of the South China Sea tide.
Results of the study indicated that:
1. There is a pretty good resemblance between model running results and results of water levels measurement. Salinity, calculated results have a larger amplitude slightly from measured data but this difference and oscillation phase can be acceptable.
2. Salinity 1 g / l - 3 g / l is increasingly encroaching into the infield under the sea level rise scenarios. Salt accounts is greater than 5 g / l and the margin of 10-15 g / l is also approaching deeply, so the future of Ho Chi Minh City will face to some water supply problems.
3. Saline in basin downstream Saigon - Dong Nai river is quite sensitive to the hydrological regime of the river, therefore, domestic regulation of irrigation reservoirs upstream can be used to push salt and improve salinity regime in the downstream part of the river
Basing on the researches in negative skin friction effect, especially practical experiences of construction on soft soil at Cuu Long delta area, this article want to show the negative skin friction effect in soft soil and suggest some methods to reduce this affect.
Basing on collecting and classifying the researches in soil mixing column method, and applying soil mixing column method at Sai Gon East West highway, this article wants to state and analysis the factors that effect strength and stability of mixing column. It also has some comments of applying this method in soil improvement.
SaiGon –DongNai (SG-DN) river system plays a vital role in developing the southern key economic triangle including Ho Chi Minh City, DongNai and BinhDuong provinces. Saltwater intrusion results from many factors and complex movements in SG–DN river system, in the midst of which are sea level rise and water regulation of upstream reservoirs. Theses causes have gradually changed the hydraulic regimes of the river system. As a result, saltwater intrusion has become seriously. In this article, the authors used mathematical models to investigate the change of saltwater boundary of the river system before and after the impact of sea level rise and the regulatory regime of the reservoirs. The findings contributed to the predicted scenarios where sea level rise and salinity boundary could be controlled through the regulation of upstream reservoirs.
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