Reliability-based analysis and design of geotechnical soil-structures and transparent granular soils for geotechnical testing

基于可靠性的土工结构设计和分析现已成为地基、挡土墙、加筋土坡和路堤等土工设计的发展方向。荷载和抗力系数设计(LRFD)是基于可靠性的设计的变体，自20世纪70年代以来一直被用于结构工程设计规范。该项目将为工程师提供使用电子表格进行LRFD校准的有用工具，从而避免使用蒙特卡罗方法模糊对不同不确定度来源对故障概率的影响的了解。一般的方法包括“理解水平”的概念，即奖励收集更多项目数据的工程师更高的阻力系数。候选应用是钢和聚合物加筋土墙和土钉加筋系统。阻力和荷载系数的校准结果将用于加拿大国家建筑规范(NBCC)和加拿大公路桥设计规范(CHBDC)的未来补充。 随机有限元方法是分析加筋边坡和路堤的一种有价值的研究工具。现在，它将扩展到土工合成加筋墙和地基。RFEM的优点在于它可以考虑土壤空间变异性对土壤结构性能的影响。提出的工作将研究非圆形随机游走技术，以寻找与RFEM相同的临界边坡破坏机制，但有可能避免过多的计算时间。该方法将应用于未加筋和加筋土坡和路堤、加筋土墙和土钉结构。 2011年，申请者、博士生Ezzein发明了第一个实用的透明代理颗粒土。从那时起，人们对研究大量的土-结构相互作用问题的兴趣和工作激增。在这项工作中，将使用一种特殊制造的平面应变仪，它允许通过透明膜观察透明土壤样品的内部。将使用数字图像相关(DIC)技术跟踪一组播种的彩绘目标。激光也将被用来照射和跟踪不同平面上的粒子，通过使用DIC的样品。这些方法将允许直接观察样品内的变形场，而不是像使用天然不透明沙子材料那样从边界测量中推断。不同的透明土在颗粒形状、大小和级配方面都有所不同。该试验将使人们更好地了解在平面应变和三轴试验中颗粒土的颗粒水平行为。宏观应力-应变特性将可用于模拟离心机和1G台架试验中使用的相同透明土壤。

Reliability-based design and analysis of geotechnical soil-structures is now accepted as the way forward in geotechnical design practice for foundations, retaining walls, reinforced slopes and embankments. Load and resistance factor design (LRFD) is a variant of reliability-based design that has been used in structural engineering design codes since the 1970s. This project will provide engineers with a useful tool for LRFD calibration using spreadsheets and thus avoid Monte Carlo methods that obscure understanding of the contributions of different sources of uncertainty to probabilities of failure. The general approach includes the concept of “level of understanding” that rewards engineers with higher resistance factors for gathering more project data. Candidate applications are steel and polymeric reinforced soil walls and soil-nail reinforced systems. Calibration outcomes for resistance and load factors will be used in future additions of the National Building Code of Canada (NBCC) and the Canadian Highway Bridge Design Code (CHBDC). The random finite element method (RFEM) is a valuable research tool for analysis of reinforced slopes and embankments. It will now be extended to geosynthetic reinforced walls and foundations. The advantage of the RFEM is that it can consider the influence of soil spatial variability on soil-structure performance. The proposed work will investigate non-circular random walk techniques to find the same critical slope failure mechanisms as the RFEM, but with the possibility to avoid excessive computation times. The method will be applied to unreinforced and reinforced soil slopes and embankments, reinforced soil walls and soil nail structures. The first practical transparent surrogate granular soil was invented by the applicant and PhD student Ezzein in 2011. Since that time there has been a proliferation of interest and work investigating a large number of soil-structure interaction problems. A specially manufactured plane strain apparatus that allows the interior of a specimen of transparent soil to be viewed through a transparent membrane will be used in this work. An array of seeded painted targets will be tracked using the digital image correlation (DIC) technique. A laser will also be used to illuminate and track particles in different planes through the specimen using the DIC. These methods will allow the deformation field within a specimen to be observed directly rather than inferred from boundary measurements which is the case using natural opaque sand materials. Different transparent soils varying with respect to particle shape, size and gradation will be investigated. The testing will provide better understanding of the particle-level behaviour of granular soils during plane strain and triaxial testing. Macro-scale stress-strain properties will be available to model the same transparent soils used in centrifuge and 1g bench-scale tests.