Defining the operational strength of peat (muskeg)

麝香草和泥炭土覆盖了加拿大18%的陆地，主要集中在北方地区。对麝香草工程特性的深入了解对于这些地区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，因为泥炭线性应变硬化，因此不会产生可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无法评估纤维结构产生的拉伸应力。我的研究和对其他人的研究的回顾导致了这样的假设，即高度纤维化的泥炭，包括纤维增强的全部效果，在拉伸应力状态下失效;在这种应力状态下的测试可以通过具有延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由Mohr-Coloumb表面很难定义。因此，目标i是量化纤维泥炭和纤维增强土中产生的拉应力;具体而言，纤维中的张力如何纳入强度并表现在破坏机制中。本研究将评估泥炭和纤维增强粘土中纤维的影响，然后了解纤维土的这种拉伸行为如何体现承载力。我和我过去的博士生观察到，在铁路路基下的泥炭中，孔隙压力（u）的季节性增加远高于静水压力，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被发现推动流体流动作为热驱动的固结机制，并降低有效强度。由此产生了一种假设，即阿尔伯塔省北方在今后30年中平均气温估计将从1.4摄氏度上升到4摄氏度以上，这将导致更长时间的加速退化和热驱动固结，而且这种对温度的敏感性有可能对北方的基础设施产生负面影响。因此，目标二是评估区域敏感性的泥炭气体生成，从而热驱动的固结和强度降低;并量化的敏感性的气体生成速率增加的温度，已观察到和预测这些地区。在加拿大不同地区的三个地点将被安装仪器，以测量在研究计划开始时产生的天然气。这些数据和热模拟将确定不同气候变化情景产生的温度分布，并评估降解和相关气体生成增加的可能性。这项研究将进一步发展的沼泽和泥炭土的性质的基本认识，从而影响北方地区的发展和加拿大的基础设施的安全性和可靠性。

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.