Incremental model for pore water pressure and its applicability in centrifuge modelling
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摘要: 超重力试验是目前岩土工程领域一种日趋成熟和广泛使用的物理试验手段，但在本构关系方面研究较少，而其在真实应力和边界条件上对本构关系研究更具明显优势。基于Ishibashi各因子乘积形式的基本思想，重点考虑有效应力、动剪应力比、循环振次和固结比等关键因子，提出了适于任意荷载和非均等固结的全因子孔压增量模型。通过自主研发的高性能孔压传感器DSP-II量测液化孔压动力时程，揭示了不同荷载、密实度、埋深条件下新孔压增量模型预测饱和砂土孔压发展过程和液化阈值的准确性与普适性。给出了不同密实度砂土的抗液化强度与计算参数，结果表明随循环动应力比的减小，初始液化触发循环振次N呈现增大规律；而随相对密度Dr的增加，抗液化强度则呈现逐渐增大规律；该模型计算的抗液化强度预测值与实测数据基本吻合，可较好地预测超重力液化试验饱和砂土的抗液化强度与变化趋势。Abstract: The centrifugal model test is an increasingly mature and widely-used physical test method. However, there is few researches on the constitutive relationship, and the researches on the constitutive relationship under the real stress and boundary conditions of the centrifugal model test have more obvious advantages. Based on the basic idea of Ishibashi multiplication of various factors, an incremental model for pore water pressure suitable for the arbitrary load and anisotropic consolidation is proposed. The applicability and reliability of the new incremental model with the test data of the DSP-II transducer is verified. The results show that the incremental model can well describe the development process of the pore water pressure of saturated sand and the liquefaction threshold under different seismic loads, relative densities and soil depths. The liquefaction resistance and the relevant parameters of saturated sand with different densities are given. With the decrease of the cyclic dynamic stress ratio of saturated sand, the initial liquefaction trigger vibration cycle time N increases gradually. With the increase of the relative density Dr of saturated sand, the liquefaction resistance also increases. The predicted data of liquefaction resistance calculated by the incremental model are basically consistent with the measured ones, which can better predict the liquefaction resistance of saturated sand in centrifugal model tests.
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图 1 DCIEM-40-300大型离心机振动台系统
Figure 1. Centrifuge shaking table test system of DCIEM-40-300
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图 4 孔压增量比与实时动剪应力比关系曲线
Figure 4. Relationship between pore water pressure increment ratio and dynamic shear stress ratio for medium dense sand
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图 5 孔压增量比与循环周数关系曲线
Figure 5. Relationship between pore water pressure increment ratio and number of cycles
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图 6 等幅和变幅正弦荷载下计算与实测孔压增长对比
Figure 6. Comparison between calculated and measured excess pore water pressures under uniform and variable amplitude sine waves
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