Levees are affected by over-exploitation of river sand and river adjustments after the formation of sand pits. The slope stability is seriously threatened, drawing wide concern among experts and scholars in the area o...Levees are affected by over-exploitation of river sand and river adjustments after the formation of sand pits. The slope stability is seriously threatened, drawing wide concern among experts and scholars in the area of water conservancy. This study analyzed the uncertainties of slope stability of levees under river sand mining conditions, including uncertainty caused by interest- driven over-exploitation by sand mining contractors, and uncertainty of the distance from the slope or sand pit to the bottom of the levee under the action of cross-flow force after the sand pit forms. Based on the results of uncertainty analysis, the distribution and related parameters of these uncertainties were estimated according to the Yangtze River sand mining practice. A risk model of the slope instability of a levee under river sand mining conditions was built, and the possibility of slope instability under different slope gradients in a certain reach of the Yangtze River was calculated with the Monte Carlo method and probability combination method. The results indicated that the probability of instability risk rose from 2.38% to 4.74% as the pits came into being.展开更多
Levees are essential structures in flood defense systems,and their failures can lead to devastating consequences on the surrounding territories.One of the failure mechanisms mostly controlled by the foundation soil st...Levees are essential structures in flood defense systems,and their failures can lead to devastating consequences on the surrounding territories.One of the failure mechanisms mostly controlled by the foundation soil stratigraphy is the instability of the land side slope,triggered by the development of high uplift pressures in the foundation.This complex phenomenon has been investigated experimentally with centrifuge tests or large-scale tests and numerically with the limit equilibrium method(LEM)and the finite element method(FEM).In this work,we applied a multiphase formulation of the material point method(MPM)to analyze the development of toe uplift instability mechanism,from the onset of failure to large displacements.The numerical model is inspired by an experiment carried out in a geotechnical centrifuge test by Allersma and Rohe(2003).The comparison with the experiment allows for understanding critical pore pressure triggering large displacements in the foundation soils.Moreover,we numerically evaluated the impact of different values of foundation soils’hydraulic conductivity on the failure mechanism.The results show that hydraulic conductivity mainly influences the time of failure onset and the extension of shear localization at depth.Finally,the advantages of using large displacement approaches in the safety assessment of earth structures are discussed.Unlike FEM,there are no issues with element distortions generating difficulties with numerical convergence,allowing for full postfailure reproduction.This capability permits precise quantification of earth structure damages and post-failure displacements.The ensuing reinforcement systems’design is no longer over-conservative,with a significant reduction in associated costs.展开更多
基金supported by the Special Fund for Public Welfare Industry of the Ministry of Water Resources of China (Grant No. 201001007)
文摘Levees are affected by over-exploitation of river sand and river adjustments after the formation of sand pits. The slope stability is seriously threatened, drawing wide concern among experts and scholars in the area of water conservancy. This study analyzed the uncertainties of slope stability of levees under river sand mining conditions, including uncertainty caused by interest- driven over-exploitation by sand mining contractors, and uncertainty of the distance from the slope or sand pit to the bottom of the levee under the action of cross-flow force after the sand pit forms. Based on the results of uncertainty analysis, the distribution and related parameters of these uncertainties were estimated according to the Yangtze River sand mining practice. A risk model of the slope instability of a levee under river sand mining conditions was built, and the possibility of slope instability under different slope gradients in a certain reach of the Yangtze River was calculated with the Monte Carlo method and probability combination method. The results indicated that the probability of instability risk rose from 2.38% to 4.74% as the pits came into being.
基金Financial supports from University of Padua(Grant No.BIRD181859)Italian Ministry of Education,University and Research(MIUR),Redreef-PRIN 2017 Call(Grant No.2017YPMBWJ)are gratefully acknowledged.
文摘Levees are essential structures in flood defense systems,and their failures can lead to devastating consequences on the surrounding territories.One of the failure mechanisms mostly controlled by the foundation soil stratigraphy is the instability of the land side slope,triggered by the development of high uplift pressures in the foundation.This complex phenomenon has been investigated experimentally with centrifuge tests or large-scale tests and numerically with the limit equilibrium method(LEM)and the finite element method(FEM).In this work,we applied a multiphase formulation of the material point method(MPM)to analyze the development of toe uplift instability mechanism,from the onset of failure to large displacements.The numerical model is inspired by an experiment carried out in a geotechnical centrifuge test by Allersma and Rohe(2003).The comparison with the experiment allows for understanding critical pore pressure triggering large displacements in the foundation soils.Moreover,we numerically evaluated the impact of different values of foundation soils’hydraulic conductivity on the failure mechanism.The results show that hydraulic conductivity mainly influences the time of failure onset and the extension of shear localization at depth.Finally,the advantages of using large displacement approaches in the safety assessment of earth structures are discussed.Unlike FEM,there are no issues with element distortions generating difficulties with numerical convergence,allowing for full postfailure reproduction.This capability permits precise quantification of earth structure damages and post-failure displacements.The ensuing reinforcement systems’design is no longer over-conservative,with a significant reduction in associated costs.
