Defining the operational strength of peat (muskeg)

定义泥炭（muskeg）的操作强度

• 批准号: RGPIN-2020-04419
• 负责人: Hendry, Michael
• 金额: $ 3.13万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=749062
• 关键词: Defining; operational; strength; peat; muskeg

Muskeg and peat soils cover 18% of Canada's landmass and is primarily concentrated within the northern regions. A strong understanding of the engineering properties of muskeg is important for the construction and maintenance of transportation infrastructure in these regions. Defining the strength of highly fibrous peats is still elusive, as peat linearly strain harden and thus does not develop a maximum value that can be defined as a strength. Further, traditional geotechnical testing methods used to evaluate peat cannot evaluate tensile stresses generated by the fibrous structure. My research and a review of others' led to the hypotheses that highly fibrous peat, inclusive of the full effects of fiber reinforcement, fails at a tensile stress state; testing at this stress state can be accomplished with triaxial tests with extension stress paths; and the strength of this type of peat is poorly defined by a Mohr-Coloumb surface. Thus, Objective i is to quantify the tensile stresses generated within fibrous peat and fiber reinforced soils; specifically, how tension in fibers are incorporated into strength and manifest in the mechanism of failure. This research will evaluate the effects of fibers in peat and fiber reinforced clays, and then develop an understanding of how this tensile behaviour of fibrous soils manifests for bearing capacity. My past PhD student and I observed the seasonal increase of pore pressure (u) in peat beneath railway embankments well above hydrostatic pressure followed by a rapid decrease. This was found to be the result of gas generation and is controlled by temperature. The presence of gas and increased pore pressure was found to push fluid flow as a thermally driven consolidation mechanism and reduce effective strength. This led to the hypothesis that the estimated increases of mean temperature from 1.4oC to > 4oC for northern Alberta over the next 30 years will result in longer periods of accelerated degradation and thermally driven consolidation and that this sensitivity to temperature has the potential to negatively impact northern infrastructure. Thus, Objective ii is to evaluate the regional susceptibility of peat to gas generation and thus thermally driven consolidation and reduced strength; and to quantify the sensitivity of the rate of gas generation to increased temperatures that have been observed and predicted for these regions. Three sites in different regions of Canada will be instrumented to measure u resulting from gas generation at the start of the research program. The data and thermal modeling will determine the temperature profiles resulting from the differing climate change scenarios and evaluate the potential for increased degradation and associated gas generation. This study will further develop a fundamental understanding of the properties of muskeg and peaty soils, and thus impact the development in northern regions and the safety and reliability of Canada's infrastructure.

麝香和泥炭土壤占加拿大陆地面积的18%，主要集中在北部地区。深入了解马赛克的工程特性对于这些地区的交通基础设施的建设和维护非常重要。定义高纤维泥炭的强度仍然是难以捉摸的，因为泥炭会线性应变硬化，因此不会产生可以定义为强度的最大值。此外，用于评估泥炭的传统土工测试方法不能评估由纤维结构产生的拉应力。我的研究和对其他人的研究的回顾导致了这样的假设：高纤维泥炭，包括纤维增强的全部效果，在拉应力状态下失效；在这种应力状态下的测试可以通过具有拉伸应力路径的三轴测试来完成；并且这种类型的泥炭的强度不能用Mohr-Coloumb表面来定义。因此，目标一是量化纤维泥炭和纤维增强土壤中产生的拉应力；具体地说，纤维中的张力如何结合到强度中并在破坏机制中表现出来。这项研究将评估纤维在泥炭和纤维增强粘土中的作用，然后发展对纤维土的拉伸行为如何表现为承载能力的理解。我和我过去的博士生观察到，在远远高于静水压力的铁路路堤下，泥炭中的孔压(U)有季节性的增加，然后迅速下降。这被发现是气体生成的结果，并受温度控制。气体的存在和孔隙压力的增加作为一种热驱动的固结机制来推动流体流动，降低了有效强度。这导致了一种假设，即未来30年，阿尔伯塔省北部的平均气温估计将从1.4摄氏度上升至4摄氏度，这将导致更长时间的加速退化和热驱动的固结，这种对温度的敏感性有可能对北部基础设施产生负面影响。因此，目标二是评估泥炭对天然气生成的区域敏感性，从而评估热驱动固结和强度降低的区域敏感性；并量化已观察到的和预测的这些区域的天然气生成速率对温度升高的敏感性。在研究计划开始时，加拿大不同地区的三个地点将被用来测量天然气产生的u。数据和热模拟将确定不同气候变化情景造成的温度分布，并评估加剧退化和相关气体产生的可能性。这项研究将进一步加深对麝香和泥炭土壤性质的基本了解，从而影响北部地区的发展和加拿大基础设施的安全和可靠性。