Fatigue behaviour of geomaterials under cyclic environmental loading

循环环境荷载下岩土材料的疲劳行为

• 批准号: RGPIN-2020-03949
• 负责人: Wong, Ron
• 金额: $ 2.26万
• 依托单位: University of Calgary
• 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=715486
• 关键词: Fatigue; behaviour; geomaterials; under; cyclic

Cyclic loadings are commonly encountered in engineering applications. Wind exerts dynamic loads on tall buildings. Wave and ice load imposes threat to offshore structures and transportation infra-structures in arctic waters. Seasonal variation of precipitation and water table imposes repeated loads on earthworks. Cyclic freezing-thawing of ground along with traffic loads affect the long-term performance of pavements and buried utilities. Natural geohazards such as earthquakes and landslides are cyclic and dynamic in essence. Mineral mining and oil and gas extraction also involve cyclic loading to the surrounding environment. The long-term objective of this proposed research program is to develop techniques to quantify fatigue behaviour and expected life span of different geomaterials under cyclic loading encountered in the field so that new technologies can be developed for prevention of hazards, protection of the Environment, and optimization of material life span and natural resource recovery. The first type of geomaterials studied in this proposed research is Montney Formation which is one of the major natural oil and gas resources in Canada. Due to its tight pore structure, hydraulic fracturing (HF) has been used for exploitation of this resource. It involves high-pressure injection of chemically treated fluid into the formation to create a fracture network enhancing oil and gas production. Potential risks to natural water sources by contamination of fracture fluid and hydrocarbons resulting from hydraulic fracturing have raised public concerns. Hydraulic fracturing also induces seismic events which may impose detrimental effects on surface facilities. There is an urgent need to modify the current HF treatment to enhance the hydraulic flow in this tight material and reduce the amount of seismic energy released from the treatment. We propose to unlock the tight material by failing it in a controllable “fatigue” manner. It is well known that materials fail in a cyclic fatigue mode under a cyclic applied stress lower than that in a monotonic mode. We postulate that a lower fracturing pressure is required to disintegrate the tight material under cyclic (pulsation) loading. Under controlled pulsation process, the fractured zone may be more homogeneous rather than localized. The first stage of the research program involves experimentation in laboratory scale. In the second stage the test data will be used and implemented to feasibility studies of small-scale field experiments. The third stage is the development of novel technologies for exploitation of Montney Formation. This research program clearly carries both scientific and socio-environmental-economic impacts. Findings from this research program are readily transferred to research fields as listed above. Technology transfer and collaboration with industrial partners and regulators address public concerns, promote protection of the Environment, and enhance our economy and employment.

循环荷载是工程应用中经常遇到的情况。风对高层建筑施加动态荷载，波浪和冰荷载对北极水域的海上结构和运输基础设施结构造成威胁，而地下水位的季节性变化对土方工程产生重复荷载。 - 地面解冻和交通负荷会影响路面和埋地公用设施的长期性能。地震和山体滑坡等自然地质灾害本质上是周期性和动态的。矿物开采和石油和天然气开采也涉及其中。该研究计划的长期目标是开发量化不同土工材料在现场遇到的循环载荷下的疲劳行为和预期寿命的技术，以便开发新技术来预防危险。 、保护环境、优化材料寿命和自然资源回收。 本研究中研究的第一类岩土材料是蒙特尼地层，它是加拿大主要的天然石油和天然气资源之一，由于其致密的孔隙结构，水力压裂（HF）已被用于开采该资源。将经过化学处理的流体高压注入地层以形成裂缝网络，从而提高石油和天然气产量。水力压裂造成的压裂液和碳氢化合物污染对天然水源造成的潜在风险引起了公众的关注。还诱发可能对地面设施造成损害影响的地震事件。 迫切需要改进当前的高频处理，以增强这种致密材料中的水力流动，并减少处理中释放的地震能量。我们建议通过以可控的“疲劳”方式破坏致密材料来解锁。众所周知，材料在循环施加应力低于单调模式下会以循环疲劳模式失效，我们假设在循环（脉动）载荷下分解致密材料需要较低的破裂压力。研究计划的第一阶段涉及实验室规模的实验，在第二阶段，测试数据将用于小规模现场实验的可行性研究。第三阶段是开发蒙特尼组开采新技术。 该研究项目显然具有科学和社会环境经济影响，很容易转移到上述研究领域，技术转让以及与工业合作伙伴和监管机构的合作解决了公众关注的问题，促进了环境的保护，并促进我们的经济和就业。