Thermal-mechanical response of frozen clay soil and the impact on soil-structure interaction

在加拿大北部，永久冻土区的冻土非常丰富，由于对资源的需求增加，新的基础设施需求正在建立。长期记录表明，持续的全球变暖导致部分永久冻土区融化，导致地面大面积沉降，并对基础设施造成破坏。了解冻土在热-力冲击作用下的行为是研究土-结构相互作用的基础，对发展寒区基础设施的安全经济设计具有重要意义。目前，关于冻土区热致强度弱化的理论研究很少，对冻土区温度相关破坏行为的数值模拟也很少。在了解冻土热诱导机械退化（弱化）的潜在机制以及这些机制如何影响基础设施的性能方面，仍然存在重大的知识差距。因此，很少有公司愿意在他们的设计中考虑冻土的热致破坏。******本研究计划是为了解决冻土工程中的热致问题而提出的。本项目的长期目标是研究冻结粘土中的热-水-机械-化学耦合过程及其对土壤结构相互作用的影响。本项目短期（5年）旨在研究饱和水冻土热致弱化的物理特性及其对土-结构相互作用的影响。它有三个目标：(1)进行实验室试验以测量不同温度下冻结粘土的力学特性；(2)提出温度相关力学特性的理论模型并在数值模拟工具中使用这些模型；(3)提出一种考虑冻结粘土温度升高的多年冻土区土壤-结构相互作用的模拟方法。这项为期5年的研究计划的完成是该计划长期范围的第一部分。******提出的研究计划将丰富土力学在温度相关主题学科中的发展。该研究项目的成果将促进工程师们积极考虑多年冻土区埋地结构设计和运行中的热-力学影响。一旦了解了这种土壤-结构相互作用的热影响，就有可能升级基础设施设计的规定，以考虑热影响。这对加拿大多年冻土区的管道建设和自然资源开发等工程项目非常有益

In northern Canada, frozen clay soil is very abundant in permafrost regions, where new infrastructure needs are being created as a result of heightened demand for resources. Long term records indicate an on-going global warming has resulted in thawing of portions of the permafrost area, which leads to extensive settlement of the ground surface and causing damage to infrastructures. Understanding the behavior of frozen soil under thermal-mechanical impact is the fundamental of studying on the soil-structure interaction, which is of significant importance to the development of safe and economical designs of infrastructures in cold regions. Currently, very little theoretical work on thermally induced strength weakening in frozen clay soil can be found, and numerical simulation on the temperature-dependent failure behavior in frozen clay soil is not available. There remains a significant knowledge gap in terms of understanding the underlying mechanisms of thermally induced mechanical degradation (weakening) of frozen clay soil and how those affect the performance of infrastructures. Consequently, very few companies would like to take into account of thermally induced failure of frozen clay soil in their designs.******This research program is proposed to put a step toward solving thermally induced problems in frozen ground engineering. The long-term scope of this program is to study thermal-hydro-mechanical-chemical coupled processes in frozen clay soils and the impact on soil structure interaction. The short-term scope (in 5 years) of this program is aimed at investigating the physics of thermally induced weakening in water-saturated frozen clay soil and the impact on soil-structure interaction. It has three objectives: (1) to perform laboratory tests to measure mechanical properties of frozen clay soil at different temperatures (2) to propose theoretical models for temperature-dependent mechanical properties and use the models in a numerical simulation tool (3) to propose an approach to simulate the soil-structure interactions in permafrost area with consideration of the temperature increase in frozen clay soils. The completion of this 5-years research program is the first part of the program's long-term scope.******The proposed research program will enrich the development of soil mechanics in the discipline of temperature related topics. The deliverables from this proposed research program will promote the interests of engineers to proactively consider thermal-mechanical impacts on designs and operations of buried structures in permafrost regions. Once the thermal impact on such soil-structure interaction is understood, it will be possible to upgrade the regulations for the design of infrastructures to account for the thermal impact. It will be very beneficial for engineering projects such as pipeline construction and natural resource exploitation in Canadian's permafrost regions.**