EAGER: Deformation Induced Soil Fracturing - Multi-Scale Multi-Physics Mechanism and Early Detection

EAGER：变形引起的土壤破裂 - 多尺度多物理机制和早期检测

• 批准号: 1741042
• 负责人: Kenichi Soga
• 金额: $ 30万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1741042&HistoricalAwards=false
• 关键词: EAGER; Deformation; Induced; Soil; Fracturing

This EArly-concept Grant for Exploratory Research (EAGER) project investigates the fundamental science of multi-scale and multi-physics processes of fractures that develop in soil while a soil mass is settling and deforming due to land subsidence, landslides or earthquakes. It seeks experimental evidence of a new theoretical model of soil fracturing. The findings will then be used to develop a field monitoring tool that provides early warning of soil fracturing. The project specifically utilizes the following two problems in geotechnical engineering as part of a case scenario-based study. The first problem is related to land subsidence induced by groundwater extraction that is prevalent in many areas of the United States. For example, in the San Joaquin Valley, California, more than half of the valley has subsided in excess of 0.3m; subsidence of 10 m and a rate of more than 0.3m/year has been reported in some areas. When differential compaction occurs near groundwater extraction wells and local variations in geology, cracks may develop in the surrounding ground. Such land subsidence induced fracture zones may be as much as 200 m wide and consist of multiple parallel, branching fissures and graben blocks. These features are reported to cause billions of dollars of damage to critical built infrastructure. However, monitoring technology that effectively gives early warning to soil fracture development is not available at present. The second problem is related to possible earthquake-induced damage of deep cut-off walls used in river levees that are constructed to reduce its flood risk. For example, the Greater Sacramento area in California is among the most at-risk regions in America for catastrophic flooding. The area relies on an aging system of levees, and massive levee improvements are currently underway. A typical improvement involves installation of deep cut off walls with additional fill to raise the levee in order to mitigate under-seepage failure of the levees. During an earthquake, the walls can be at risk of fracturing as the levee system deforms. As a consequence, the ability to control seepage in a future flooding event may be lost. Again, an early warning monitoring system is needed to assess the risk of such soil fractures during the lifetime of operation.When soil fracture occurs, it is likely to be localized and scale-dependent and therefore the locations of the failure will be difficult to predict. This uncertainty in the soil fracturing process can potentially lead to significant engineering issues and any monitoring technology that provides early detection is needed. To make a step change in our fundamental understanding of soil fracturing process, experimental evidence that supports new theoretical models and tools to measure it in the field are required. This project aims to explore for the experimental evidence of multi-physics and multi-scale soil-pore water interaction occurring during deformation induced soil fracture initiation and propagation and to demonstrate the feasibility of high resolution distributed fiber optic strain sensing technology for detecting an early signature of soil fracturing. The primary goals of the project are (i) test for experimental evidence of multi-physics and multi-scale soil-pore water interaction occurring during deformation induced soil fracture initiation and propagation, and (ii) to demonstrate the feasibility of high resolution distributed fiber optic strain sensing technology for detecting an early signature of soil fracturing. In this project, a series of flexural tests will be performed on soil beam specimens, in which miniature pore pressure transducers and fiber optic sensing cables will be embedded. The project will investigate the excess pore pressure generation and dissipation during the soil fracture initiation and propagation process. It is hypothesized that different micro-scale failure modes inside a fracture process zone would be captured by high resolution distributed fiber optic strain sensing technology. The feasibility of the technology for a field-based early warning system against soil fracturing will be examined.

这个早期概念探索性研究资助（EAGER）项目研究了土壤中裂缝的多尺度和多物理过程的基础科学，而土壤由于地面沉降，滑坡或地震而沉降和变形。 它寻求土壤破裂的新理论模型的实验证据。 研究结果将用于开发一种现场监测工具，提供土壤破裂的早期预警。 该项目特别利用岩土工程中的以下两个问题作为基于案例的研究的一部分。 第一个问题与美国许多地区普遍存在的地下水开采引起的地面沉降有关。 例如，在加州的圣华金河谷，超过一半的河谷已经下沉超过0.3米;在某些地区，已经报告了10米的下沉和超过0.3米/年的速度。 当地下水抽取威尔斯井附近发生不均匀压实和地质局部变化时，周围地面可能会出现裂缝。 这种地面沉降引起的断裂带可能高达200米宽，由多个平行的分支裂缝和地堑块体组成。 据报道，这些特征会对关键的建筑基础设施造成数十亿美元的损失。然而，目前还没有有效地对土壤裂缝发育进行预警的监测技术。 第二个问题是，为减少洪水风险而建造的河堤中使用的深层防渗墙可能会因地震而受损。 例如，加州的大萨克拉门托地区是美国灾难性洪水风险最高的地区之一。 该地区依赖于老化的堤坝系统，目前正在进行大规模的堤坝改善。 一个典型的改进包括安装深截渗墙，并增加填料，以提高堤坝，从而减轻堤坝的渗透破坏。 在地震期间，由于堤坝系统变形，墙壁可能有破裂的危险。 因此，在未来的洪水事件中可能会失去控制渗漏的能力。同样，需要一个早期预警监测系统，以评估在运行寿命期间发生此类土壤破裂的风险。当土壤破裂发生时，它可能是局部的，并取决于规模，因此，故障的位置将难以预测。土壤压裂过程中的这种不确定性可能会导致重大的工程问题，因此需要任何能够提供早期检测的监测技术。为了改变我们对土壤破裂过程的基本理解，需要实验证据来支持新的理论模型和工具来测量它。 本项目旨在探索多物理场和多尺度土壤-孔隙水相互作用在变形诱导的土壤裂缝的形成和扩展过程中发生的实验证据，并论证高分辨率分布式光纤应变传感技术用于检测土壤破裂早期特征的可行性。 该项目的主要目标是：（i）测试在变形引起的土壤裂缝开始和扩展过程中发生的多物理场和多尺度土壤-孔隙水相互作用的实验证据，以及（ii）证明高分辨率分布式光纤应变传感技术用于检测土壤裂缝早期特征的可行性。 本计画将于土梁试件上进行一系列的弯曲试验，并将微型孔压感测器及光纤感测缆埋设于土梁试件中。 本项目将研究在土壤破裂开始和扩展过程中超孔隙压力的产生和消散。 据推测，不同的微观尺度内的断裂过程区的破坏模式将被捕获的高分辨率分布式光纤应变传感技术。将审查该技术用于防止土壤破裂的实地预警系统的可行性。

项目成果

Brillouin scattering spectrum-based crack measurement using distributed fiber optic sensing

• DOI: 10.1177/14759217211030913
• 发表时间: 2021-07
• 期刊: Structural Health Monitoring
• 作者: Ruonan Ou;Linqing Luo;K. Soga