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，Ortiz模型应加以改进。建立本构模型需要积累土体的脆性和延性特性的试验数据。在重复加载试验中，土体的裂隙数目比重复加载试验中的多，在等幅值情况下，中空-圆柱形扭转剪切试验。裂缝面积与剪切刚度之间的关系很强，与剪切试验的幅值以及反向加载和重复加载的差异无关。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土的拉伸劈裂试验表明，土体在较快加载时具有较大的抗拉强度。本文对基于可液化土层的河堤液化变形进行了二维有限元分析。结果表明，现有的地震评估方法可能高估了俯冲地震时河堤的安全性，因此有必要应用累积损伤的概念进行地震评估。(4)研究结果表明，基于断层破裂过程和场地效应的评估方法适用于大面积堤防的破坏评估。(5)发展了基于移动粒子半隐式方法的变形分析方法，用于考虑拉伸破坏的堤防大变形评估。该方法可用于可液化地基微型模型变形形状的评价。

(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.