Zhang Fuguang, Chen Cheng, Feng Huaiping
State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures, Shijiazhuang Tiedao University, Shijiazhuang 050043, China.
Key Laboratory of Roads and Railway Engineering Safety Control (Shijiazhuang Tiedao University), Ministry of Education, Shijiazhuang 050043, China.
Materials (Basel). 2024 Jul 27;17(15):3721. doi: 10.3390/ma17153721.
This study investigates the post-liquefaction monotonic undrained shearing behavior of cemented sand at the macro- and microscales, using the discrete element method. A series of cyclic undrained triaxial tests with different stress amplitudes and post-liquefaction monotonic undrained triaxial tests were simulated on cemented sand with diverse cement contents (CCs). For comparison, a series of monotonic undrained triaxial tests on cemented sand without liquefaction (virgin cemented sand) were also modeled. The macroscopic behavior was analyzed in conjunction with the microscopic characteristics of the assembly, such as the deviator fabric of contact normal orientation, mechanical coordination number, energy components, and bond breakage. The results show that the DEM model can capture the effect of CC and cyclic stress ratio (CSR) on the undrained shear strength, stiffness, and pore pressure observed in laboratory experiments. Referring to the virgin specimen, with an increase in CC, the mechanical coordination number and the input work increment increase, while the deviator fabric for total contacts changes irregularly, leading to a greater initial stiffness and shear strength. In the case of the liquefied specimen, the smaller initial mechanical coordination number results in a very low initial stiffness regardless of CC. Contrary to the uncemented sand, both the mechanical coordination number and the input work increment decrease with an increasing CSR for the cemented sand. The microstructure evolution governs the effect of cementation level and liquefaction history on the macroscopic post-liquefaction behavior.
本研究采用离散元方法，从宏观和微观尺度研究了胶结砂液化后的单调不排水剪切行为。对不同水泥含量（CC）的胶结砂进行了一系列不同应力幅值的循环不排水三轴试验和液化后单调不排水三轴试验。为作比较，还对未液化的胶结砂（原状胶结砂）进行了一系列单调不排水三轴试验建模。结合颗粒集合体的微观特征，如接触法线方向的偏应力织物、力学配位数、能量分量和粘结破坏，对宏观行为进行了分析。结果表明，离散元模型能够捕捉到水泥含量（CC）和循环应力比（CSR）对实验室试验中观察到的不排水抗剪强度、刚度和孔隙水压力的影响。与原状试样相比，随着水泥含量的增加，力学配位数和输入功增量增加，而总接触的偏应力织物变化不规则，导致初始刚度和抗剪强度更大。对于液化试样，无论水泥含量如何，较小的初始力学配位数都会导致非常低的初始刚度。与无胶结砂相反，胶结砂的力学配位数和输入功增量均随循环应力比的增加而减小。微观结构演化决定了胶结水平和液化历史对宏观液化后行为的影响。
