In this work, the yield stress evaluation as a function of water content for slip-prone clayey soils is studied in order to understand how yield stress decreases as water content increases, and their relation with the...In this work, the yield stress evaluation as a function of water content for slip-prone clayey soils is studied in order to understand how yield stress decreases as water content increases, and their relation with the chemical properties. The clayey soil samples were taken from the region of Teziutlán-Puebla-Mexico. Yield stress was calculated using the slump test in cylindrical geometry. Results show three zones. The first one shows an exponential decrement on yield stress due to lower water content in accord with clayey soils with high content of illita, followed by a second region where yield stress decreases dramatically at a certain critical water concentration, and the third one where yield stress dependence is not well-defined since the clayey soil flow is seen. Finally, it is discussed how yield stress variation due to the water increment influences the landslide risk increment.展开更多
针对扰动饱和水田土壤环境下触土工作部件与土壤间相互作用关系需要,对高含水率、高流变性和高粘附性的扰动饱和水田土壤离散元仿真模型开展了研究。基于坍落度试验,利用EDEM软件中的Hertz-Mindlin with JKR接触模型构建了土壤颗粒和水...针对扰动饱和水田土壤环境下触土工作部件与土壤间相互作用关系需要,对高含水率、高流变性和高粘附性的扰动饱和水田土壤离散元仿真模型开展了研究。基于坍落度试验,利用EDEM软件中的Hertz-Mindlin with JKR接触模型构建了土壤颗粒和水颗粒二相混合模型,对扰动饱和水田土壤进行离散元仿真参数标定。以坍落拓展度w为试验指标,利用Plackett-Burman试验从8个相关参数中筛选出对拓展度影响显著的3个参数,其中土壤-水间JKR表面能和土壤-土壤间滚动摩擦因数对拓展度影响极显著,土壤-土壤间恢复系数对拓展度影响显著。根据Box-Behnken试验建立并优化拓展度与显著性参数的二阶回归模型,获得最优参数组合为:土壤-土壤间恢复系数为0.402,土壤-土壤间滚动摩擦因数为0.136,土壤-水颗粒间JKR表面能为0.920 J/m^(2)。基于标定后的参数组合,以滑板牵引阻力为指标,进行水稻直播机播种滑板模型与扰动饱和水田土壤间互作关系仿真模拟及土槽试验验证,结果表明仿真与试验获得的滑板模型阻力误差为6.46%,扰动饱和水田土壤离散元仿真模拟与试验一致,表明本研究参数标定方法准确可行。研究可为该类型土壤下的农业机械及触土部件的相关研究奠定基础与提供支撑。展开更多
The discrete element method (DEM) was used to simulate the flow characteristic and strength characteristic of the conditioned sands in the earth pressure balance (EPB) tunneling. In the laboratory the conditioned sand...The discrete element method (DEM) was used to simulate the flow characteristic and strength characteristic of the conditioned sands in the earth pressure balance (EPB) tunneling. In the laboratory the conditioned sands were reproduced and the slump test and the direct shear test of the conditioned sands were implemented. A DEM equivalent model that can simulate the macro mechanical characteristic of the conditioned sands was proposed,and the corresponding numerical models of the slump test and the shear test were established. By selecting proper DEM model parameters,the errors of the slump values between the simulation results and the test results are in the range of 10.3%-14.3%,and the error of the curves between the shear displacement and the shear stress calculated with the DEM simulation is 4.68%-16.5% compared with that of the laboratory direct shear test. This illustrates that the proposed DEM equivalent model can approximately simulate the mechanical characteristics of the conditioned sands,which provides the basis for further simulation of the interaction between the conditioned soil and the chamber pressure system of the EPB machine.展开更多
文摘In this work, the yield stress evaluation as a function of water content for slip-prone clayey soils is studied in order to understand how yield stress decreases as water content increases, and their relation with the chemical properties. The clayey soil samples were taken from the region of Teziutlán-Puebla-Mexico. Yield stress was calculated using the slump test in cylindrical geometry. Results show three zones. The first one shows an exponential decrement on yield stress due to lower water content in accord with clayey soils with high content of illita, followed by a second region where yield stress decreases dramatically at a certain critical water concentration, and the third one where yield stress dependence is not well-defined since the clayey soil flow is seen. Finally, it is discussed how yield stress variation due to the water increment influences the landslide risk increment.
文摘针对扰动饱和水田土壤环境下触土工作部件与土壤间相互作用关系需要,对高含水率、高流变性和高粘附性的扰动饱和水田土壤离散元仿真模型开展了研究。基于坍落度试验,利用EDEM软件中的Hertz-Mindlin with JKR接触模型构建了土壤颗粒和水颗粒二相混合模型,对扰动饱和水田土壤进行离散元仿真参数标定。以坍落拓展度w为试验指标,利用Plackett-Burman试验从8个相关参数中筛选出对拓展度影响显著的3个参数,其中土壤-水间JKR表面能和土壤-土壤间滚动摩擦因数对拓展度影响极显著,土壤-土壤间恢复系数对拓展度影响显著。根据Box-Behnken试验建立并优化拓展度与显著性参数的二阶回归模型,获得最优参数组合为:土壤-土壤间恢复系数为0.402,土壤-土壤间滚动摩擦因数为0.136,土壤-水颗粒间JKR表面能为0.920 J/m^(2)。基于标定后的参数组合,以滑板牵引阻力为指标,进行水稻直播机播种滑板模型与扰动饱和水田土壤间互作关系仿真模拟及土槽试验验证,结果表明仿真与试验获得的滑板模型阻力误差为6.46%,扰动饱和水田土壤离散元仿真模拟与试验一致,表明本研究参数标定方法准确可行。研究可为该类型土壤下的农业机械及触土部件的相关研究奠定基础与提供支撑。
基金Project (2007CB714006) supported by the National Basic Research Program of China
文摘The discrete element method (DEM) was used to simulate the flow characteristic and strength characteristic of the conditioned sands in the earth pressure balance (EPB) tunneling. In the laboratory the conditioned sands were reproduced and the slump test and the direct shear test of the conditioned sands were implemented. A DEM equivalent model that can simulate the macro mechanical characteristic of the conditioned sands was proposed,and the corresponding numerical models of the slump test and the shear test were established. By selecting proper DEM model parameters,the errors of the slump values between the simulation results and the test results are in the range of 10.3%-14.3%,and the error of the curves between the shear displacement and the shear stress calculated with the DEM simulation is 4.68%-16.5% compared with that of the laboratory direct shear test. This illustrates that the proposed DEM equivalent model can approximately simulate the mechanical characteristics of the conditioned sands,which provides the basis for further simulation of the interaction between the conditioned soil and the chamber pressure system of the EPB machine.
