液化土层上建筑物倾斜计算要点初步分析

Key points for calculating inclination of buildings on liquefiable soil layers

地震中饱和砂土地基液化会引起结构物倾斜并导致其功能丧失,但目前缺乏相应的数值模拟方法。通过振动台简单模型试验,寻找输入波-基底竖向动应力-基底孔压-结构震陷之间的关系,提出发展液化土层上建筑物倾斜数值模拟方法所需要考虑的要点和应满足的条件。结果表明:(1)分析方法中孔压增长模型应适于不规则波计算,能准确地计算出孔压增长过程,准确地计算出峰值一样但不同波形下孔压增长的差别;(2)孔压增长模型应能反映土的各向异性特性对孔压增长的影响,能合理地计算出拉、压不同应力作用下孔压增长的差异;(3)孔压增长模型应能反映非均等固结条件对孔压增长过程的影响,能合理地计算出结构底部不同固结比土体中孔压增长过程;(4)分析方法中土体变形的计算应能跟踪液化过程中的变形发展,且具备大变形计算能力。

The liquefaction in earthquakes will cause the inclination of the buildings and lead to their loss of functions. No numerical methods,however,can simulate the behavior of the phenomena at present. To search for the key points in the potential numerical method of calculating the building inclination due to soil liquefaction,the simple shaking table test is conducted and the relationship of the inputting waves,the vertical dynamic stresses,the pore water pressures and the building settlements are investigated in the paper. The results indicate:(1) The pore water pressure model used in the potential method must be suitable for simulating the process of water pressure rising during the irregular loads and can exactly calculate the difference of the pore water pressures under the incident loads with same peak amplitude but different forms;(2) The pore water pressure model should be able to disrcribe the pore water pressure variation due to the anisotropic property of soil and can distingush the difference of the water pressures due to the compression and extension stresses;(3) The pore water pressure model should be able to calculate the effect of the consolidation ratios on the pore water pressure variation and can attain the actual process of water pressure for the soil below the buildings;(4) The potential method should be able to follow the tracks of the deformation process of the soil layers with the increase in the pore water pressure.