Development of a seismic damage evaluation method for embankments considering tensile failure of soil

(1)研究了各向异性弹性常数的变化和滞后对应力-应变关系和裂纹的影响，在循环加载情况下，应改进Ortiz模型。建立土的本构模型需要积累有关土的脆弱性和延性特性的试验数据。在等幅、空心柱扭剪试验中，反向加载试验的土体裂缝数大于重复加载试验的土体裂缝数。裂缝面积与抗剪刚度之间的关系较强，且与剪切试验幅值以及反向和重复加载试验的差异无关。拉伸裂缝对土体的强度和变形有很大的影响。(2)不同加载速率下高岭石粘土的拉伸劈裂试验表明，加载速度越快，土的抗拉强度越大。我们认为这种效应是由吸力引起的。(3)基于可液化土层对河堤液化变形进行了二维有限元分析。研究结果表明，现有的地震评价方法可能高估了河堤在俯冲地震中的安全性，因此在地震评价中应用累积损伤的概念是必要的。(4)研究结果表明，基于断层破裂过程和场地效应的评价方法可用于大面积堤防的损伤评估。(5)针对考虑拉伸破坏的路堤大变形估计，提出了基于移动粒子半隐式法的变形分析方法。该方法可用于具有可液化地基的微缩模型的变形形态评价。

(1)We studied about the effect of the change and hysteresis of anisotropic elastic constants, on the stress-strain relationship and the crackThe Ortiz model should be improved in case of cyclic loading.Accumulation of experimental data on vulnerability and ductility characteristic of soil is necessary for the establishment of the constitutive model.The number of cracks of soil on the reversed loading tests is larger than in the case of the repeated loading tests, for equal amplitude, hollow-cylindrical torsional shear tests.The relationship between the area of crack and the shear stiffness is strong and is independent of the amplitude of shear test and the difference between the reversed and repeated loading test.The tensile crack has a strong influence on the strength and deformation of soil.(2)Tensile splitting tests of kaolinite clay for different loading rates, show that soil has a larger tensile strength during faster loading. We consider that this effect is induced by suction.(3)We performed 2 dimensional FEM analyses for liquefaction-induced deformation for river dikes based on liquefiable soil layers. The results show that the seismic evaluation by the current methods may overestimate the river dikes safety during a subduction earthquake, and therefore application of the cumulative damage concept is necessary for the seismic evaluation.(4)Our results suggest that the evaluation methodology based on fault rupture process and site effect is useful for the damage estimation of embankments spread over a wide area.(5)We developed the deformation analytical methodology based on the moving particle semi-implicit method for the large deformation estimation of embankment considering tensile failure. Our methodology may be applied for the evaluation of deformed shape of a miniature model with liquefiable ground.