垂向动载下饱和砂土液化发展的数值模拟

针对一维应变情况，建立了垂向荷载作用时饱和砂土的一维应变动力学模型，然后进行了分析。得到了在垂向荷载作用下，饱和砂土液化发展过程的特性。结果表明，渗透系数越小，骨架强度越低，扰动强度越大，液化发展越快。

NUMERICAL SIMULATION OF LIQUEACTION OF SATURATED SAND UNDER VERTICAL VIBRATION LOADING

From the sixties to nineties significant progress had been made in understanding the development of liquefaction of saturated sand under shear vibration loading, but few researchers paid attention to the responses to vertical vibration loading. Nevertheless, whether in earthquake or in blast conditions, vertical vibration has the same magnitude as shear vibration or is even larger. Therefore, this paper aims at analyzing the effect of vertical vibration loading on the development of liquefaction. One-dimensional dynamic model of saturated sand has been presented on the basis of two phase continuum theory and a constitative relation between effective stress and strain under laterally constrained condition. In this model the skeleton is considered as a plastic material and the permeability is related to the porosity. Because the pressure is not so high that the compressibility of water and soil grains can be neglected under general vibration conditions. Two important characteristics are studied, i.e., the development of material liquefactinn and the expansion of liquefaction region. The numerical results show that vertical vibration consid- erably affects liquefaction of saturated sand. Liquefaction occurs locally near the end of loading and expands afterwards under vertical vibration. The expanding velocity of liquefaction region becomes smaller and smaller with the expansion of liquefaction region because of the irreversible dissipation. If the skeleton's compressibility is large, which means the tangeds modulus is small and the limit strain is large, the development of liquefaction is fast; if the intensity of loading is large, which means the amplitude and the frequency of loading are large, the development of liquefaction is fast; and if the permeability is small, liquefaction develops fast. These characteristics show that the effect of vertical vibration on the liqbefaction of saturated sand can not be neglected in engineering design. In order to prevent liquefaction hazards caused by vertical vibration, it is necessary to make sand dense and weaken the intensity of loading. By comparing the results of ours with others, it is shown that our analysis is rational.