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

通过非线性动态模拟对地震灾害进行先进的土壤本构建模

• 批准号: RGPIN-2017-05756
• 负责人: Yniesta, Samuel
• 金额: $ 1.46万
• 依托单位: École Polytechnique de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=711790
• 关键词: Advanced; Constitutive; Modelling; Soils; Characterization

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.

加拿大东部的地质条件使对地震危险的评估挑战。基岩顶部的柔软土壤层，例如敏感的粘土，可以产生大型应变，显着放大地面运动，并导致运动比其他地质环境更大。例如，在1988年的Saguenay地震中，蒙特利尔最佳酒店De Ville被损坏，尽管距地震的中心距离酒店300公里，但仍被拆除。建筑物下面的粘土层厚17m，被评估为建筑物灭亡的主要原因。地震波还会在敏感的粘土中引起地震诱导的滑坡，因为它们容易受到环状软化的影响，其特征是循环载荷引起的刚度丧失。 通过模拟（站点响应分析）或经验位点因素来估计位点扩增或消除地面运动的趋势。可以使用线性，等效线性或非线性方法进行仿真。事实证明，非线性模拟比剪切菌株大于0.1％的等效线性模拟更为精确，但是它们需要复杂的本构模型，并且在计算上要求更高。 经验位点因子通常基于记录的地面运动和等效线性模拟的组合。对于柔软的土壤剖面，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轮廓，这些位点因素可能是不准确和不安全的。这些类型的站点因素被得出仅捕获一维站点效应，但是多维场地效应（例如盆地效应和地形放大）也可以控制现场响应。这种复杂的效果只能通过2D或3D非线性模拟捕获，但是后者很复杂，因为现有的本构模型通常需要复杂的校准过程，并且通常不会正确地对土壤的动态行为进行建模，尤其是在大型菌株下。 第一个短期目标是创建两个构成模型，用于站点响应分析和涉及适合从业者需求的环状软化的问题，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组合数据和非线性模拟来为1D和2D站点因素提供回归模型，这将降低不确定性，从而纠正对软土谱的偏见。第三个短期目标是根据现有情况和模拟得出回归模型，以使地震负载下敏感粘土中的斜率失败。长期目标是更好地了解地震危害，并为行业提供更好的工具，以促进对地震危害的评估。