Advanced Constitutive Modelling of Soils for Characterization of Seismic Hazard through Nonlinear Dynamic Simulations

加拿大东部的地质条件使地震灾害评估具有挑战性。基岩顶部的软土层，如敏感粘土，会产生大应变，显著放大地面运动，并导致运动传播到比其他地质环境更远的地方。例如，在1988年的萨盖奈地震中，蒙特利尔-Est Hotel de Ville酒店遭到破坏，尽管距离震中300公里，但不得不拆除。建筑下面的粘土层有17米厚，这被评估为建筑倒塌的主要原因。地震波还可以在敏感粘土中引起地震诱发的滑坡，因为它们对循环软化很敏感，循环软化的特征是循环荷载引起的刚度损失。场地放大或减弱地面运动的趋势可以通过模拟(场地反应分析)或经验场地因素来估计。可以使用线性、等价的线性或非线性方法来执行模拟。在剪切应变大于0.1%的情况下，非线性模拟比等效线性模拟更精确，但它们需要复杂的本构模型，并且对计算要求更高。经验场地系数通常基于记录的地面运动和等效的线性模拟的组合。对于软土剖面，由于等效线性模拟的局限性以及记录的地面运动数据库中缺乏软土剖面，这些场地系数可能是不准确和不安全的。这些类型的场地系数仅用于捕捉一维场地效应，但多维场地效应(如盆地效应和地形放大)也可以控制场地响应。这种复杂的影响只能通过2D或3D非线性模拟来捕捉，但后者是复杂的，因为现有的本构模型通常需要复杂的校准过程，并且通常不能正确地模拟土壤的动态行为，特别是在大应变下。*第一个短期目标是为现场响应分析和涉及循环软化的问题创建两个本构模型，以适应从业者的需要，其中工程师可以输入所需的行为，而不是复杂的参数。第二个短期目标是通过结合数据和非线性模拟来提供一维和二维场地因素的回归模型，这将减少不确定性，从而纠正对软土剖面的偏差。第三个短期目标是在现有实例和模拟的基础上，建立一个回归模型，用于计算敏感粘土中斜坡在地震荷载作用下的破坏概率。长期目标是更好地了解地震危险，并为业界提供更好的工具，以促进地震危险的评估。

The geological conditions in Eastern Canada make the assessment of seismic hazard challenging. Soft soil layers, such as sensitive clays, atop the bedrock can develop large strains, significantly amplify ground motion, and cause the motion to propagate much further than other geological settings. For example, in the 1988 Saguenay earthquake, the Montreal-Est Hotel de Ville was damaged and had to be torn down despite being situated 300km away from the earthquake's epicenter. The clay layer beneath the building was 17m thick, which was assessed to be the main cause of the building's demise. The seismic waves can also cause seismically induced landslides in sensitive clays because they are susceptible to cyclic softening, which is characterized by a loss of stiffness induced by cyclic loading.******The tendency of a site to amplify or de-amplify ground motion is estimated either with simulations (site response analyses) or empirical site factors. Simulations can be performed using linear, equivalent linear, or nonlinear methods. Nonlinear simulations have proven to be more precise than equivalent linear simulations at shear strains greater than 0.1%, but they require complex constitutive models and are more computationally demanding. Empirical site factors are generally based on a combination of recorded ground motions and equivalent linear simulations. For soft soil profiles, these site factors can be inaccurate and unsafe because of the limitation of equivalent linear simulations and the lack of soft soil profiles in the database of recorded ground motions. These kinds of site factors are derived to capture only 1D site effects, but multidimensional site effects such as basin effects and topographic amplification can also govern site response. Such complex effects can only be captured through 2D or 3D nonlinear simulations, but the latter are complicated because existing constitutive models often require a complex calibration process and often do not model the dynamic behaviour of soils properly, especially at large strains.******The first short term objective is to create two constitutive models for both site response analysis and problems involving cyclic softening adapted to the need of practitioners, where engineers can input a desired behaviour, instead of complex parameters. The second short term objective is to provide regression models for 1D and 2D site factors by combining data and nonlinear simulations, which will reduce uncertainty and thus correct the bias toward soft soil profiles. The third short term objective is to derive a regression model, based on existing cases and simulations, for the probability of the failure of slopes in sensitive clays under earthquake loading. The long term objectives are to gain a better understanding of seismic hazard and to provide better tools to the industry to facilitate the assessment of seismic hazard.