基于触变流体理论的可液化土体振动孔压模型
Dynamic pore water pressure model for liquefiable soils based on theory of thixotropic fluid
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摘要: 明确可液化土体的振动孔压增长过程是土体液化分析和液化效应评价的关键问题。基于Moore型触变性流体结构理论,利用不同类型土体的32个不排水循环三轴试验证实了液化过程中的土体内部结构的破坏过程与振动孔压增长过程存在等价关系,验证了循环荷载下可液化土体的孔压触变机制。在此基础上,基于孔压触变流体速率方程构建了可液化土体的振动孔压增长模型,发现模型蕴含的振动孔压产生和增长机制可从能量角度获得合理解释。试验结果表明,模型中的振动孔压增长速率参数与土体有效围压、初始相对密度及循环应力比密切相关。利用该模型对不排水循环三轴试验进行了仿真模拟,验证了模型的合理性和可靠性。最后,讨论了模型的主要特点及可能的应用前景,为土体液化分析提供一种新的技术手段。Abstract: It is a key problem to confirm the growth process of dynamic pore pressure of the liquefiable soils in the analysis of liquefaction potential of soils or evaluation of liquefaction effect. Based on the structural theory of the Moore thixotropic fluid, 32 groups of undrained cyclic triaxial experiments on different types of soils are performed to verify the corresponding relationship between internal structure parameters of soils and dynamic pore pressure in the whole liquefaction process. The thixotropic mechanism induced by the pore water pressure in the liquefiable soils under cyclic loading is confirmed. Moreover, a dynamic pore pressure growth model for the liquefiable soils is proposed based on the rate equation for the thixotropic fluid induced by pore pressure. It is found that the generation and growth mechanism of dynamic pore pressure implied in the proposed model can be explained reasonably from the viewpoint of energy. The experimental results show that the parameter of growth rate of dynamic pore pressure in the model is closely related to the effective confining pressure, initial relative density and cyclic stress ratio. The proposed model is used to simulate the undrained cyclic triaxial experiments, and accordingly the rationality and reliability of the model are proved. Finally, the main characteristics and potential applications of the proposed model are discussed. This study provides a new technical means for the liquefaction analysis of soils.