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

基本信息

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

项目摘要

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.

这项探索性研究（急切）项目的早期概念赠款研究了在土壤中发展的多尺度和多物理过程的基础科学，而土壤质量由于土壤沉降，土地沉降，山体滑坡或地震而导致土壤质量和变形。它寻求一种新的土壤破裂理论模型的实验证据。然后，这些发现将用于开发一种现场监控工具，该工具提供了土壤破裂的预警。该项目专门利用了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。第一个问题与在美国许多地区普遍存在的地下水提取引起的土地沉降有关。例如，在加利福尼亚州的圣华金山谷中，超过一半的山谷的平息超过0.30万；在某些地区报告了10 m的沉降率超过0.3m/年。当地下水提取井附近发生差异压实和地质局部变化时，周围地面可能会出现裂缝。这样的土地沉降引起的裂缝带的宽度可能高达200 m，由多个平行的分支裂缝和抓块组成。据报道，这些功能会对关键的建筑基础设施造成数十亿美元的损害。但是，目前尚不可用监测有效发出土壤骨折发育预警的技术。第二个问题是与河堤中使用的深层截止墙的可能造成的地震损坏有关，这些墙壁用于降低其洪水风险。例如，加利福尼亚州的大萨克拉曼多地区是美国灾难性洪水最高的地区之一。该地区依赖于堤防的老化系统，目前正在进行大规模的堤防改善。一个典型的改进是安装深切墙，并额外填充以增加堤防，以减轻堤坝的差异故障。在地震期间，随着堤防系统的变形，墙壁可能有破裂的风险。结果，在未来的洪水事件中控制渗流的能力可能会丢失。同样，需要一个预警监测系统来评估运行一生中这种土壤骨折的风险。当发生土壤骨折时，可能会定位并依赖于规模，因此失败的位置将难以预测。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，并且需要任何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，需要实验性证据支持新的理论模型和工具以在现场进行测量。该项目旨在探索在变形引起的土壤断裂开始和传播过程中发生多物理学和多尺度土壤孔相互作用的实验证据，并证明了高分辨率分布式光纤应变感应技术的可行性，以检测早期的土壤分裂的早期签名。该项目的主要目标是（i）测试在变形诱导的土壤断裂引发和传播过程中发生多物理和多尺度土壤孔相互作用的实验证据，以及（ii）以证明高分辨率分布式光纤菌株感应技术的可行性，以检测土壤脱脂液的早期特征。在这个项目中，将对土壤束样品进行一系列弯曲测试，其中微型孔隙压力传感器和光纤传感电缆将嵌入。该项目将在土壤断裂开始和繁殖过程中调查过量的孔隙压力产生和耗散。假设裂缝过程区域内的不同微尺度故障模式将由高分辨率分布式光纤应变感应技术捕获。该技术对针对土壤破裂的现场预警系统的可行性将进行检查。