Collaborative Research: Fiber-Optic Strain Monitoring of Rock Masses in Large Underground Facilities

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。位于南达科他州铅的8000英尺深的Homestake矿是一个深地下科学和工程实验室(Dusel)的拟议选址。它今天作为桑福德地下科学和工程实验室(Susel)运营，同时正在进行改造，准备建设。尽管洪水淹没了4520英尺深的矿井，但水泵已将水位降至4850英尺以下，并计划继续降水至8000英尺以下。此外，预计将挖掘50至60米跨度的大型房间，以容纳中微子探测器。这些活动为解决长期存在的地球科学和地球工程问题提供了近期和长期的机会，这些问题涉及从厘米到数百米的空间尺度和从毫秒到几十年的时间尺度上的岩石的力学和水文响应。本研究的目的是：(1)加深对岩石变形的多尺度、多时间尺度的认识；(2)推进岩石变形的表征技术。此外，我们认为这个项目有助于检验这样一种假设，即临界应力裂缝在前一矿内发现的裂缝范围内进行水力传导。这项工作还将展示变形与岩石特性的关系。我们的研究工作是三所美国大学、东京大学、日本原子能机构和私人公司之间的合作伙伴关系。美国团队将在Susel部署基于光纤布拉格光栅(FBG)和分布式应变和温度(DST)光纤传感器的当前最先进的变形监测技术。FBG和DST传感器将安装在4100英尺和4850英尺的水平上，安装在计划中的物理实验室附近的房间和巷道中。这些传感器将在几百米的范围内提供米尺度的测量。还将在2000英尺、4100英尺和4850英尺的深度水平部署一组倾斜仪，以提供对固体潮汐敏感的变形测量，其长度范围在10米到100米之间。温度传感光纤将被放置在6号风的水中，深至8000英尺深，放置在较短的井眼中，并沿着漂流墙放置，以监测水的流入。在补充研究中，日本团队将在Aburatsubo的地下金库以及Horonobe和Mizunami的深层地下实验室部署光纤监测阵列。他们还将改进FBG变形监测技术，将分辨率提高一到两个数量级。UBroader的影响：(1)美国研究团队将获得国际视野和知识。来自威斯康星州、南卡罗来纳州和蒙大拿州的研究生将接受多机构、多学科研究方面的培训。(2)将加强对蒙大拿州和南达科他州EPSCoR(刺激竞争性研究的实验计划)高中和大学阶段的学生和教师的培训。(3)多学科连接将加速结构健康监测光纤技术的发展。(4)原型光纤传感器网络将向Susel的人员提供有关其能力的第一手操作信息。该方法和研究数据将有助于杜塞尔的设计、建造和安全运营。

This award is funded under the American Recovery and Reinvestment Act of 2009(Public Law 111-5).The 8000-ft deep Homestake Mine in Lead, SD is the proposed site for a Deep Underground Science and Engineering Laboratory (DUSEL). It is being operated today as the Sanford Underground Science and Engineering Laboratory (SUSEL) while it is being converted to readiness for construction. Although water flooded the mine up to the 4520-ft depth level, pumps have brought the water level below 4850-ft depth with plans to continue dewatering down to 8000 feet. In addition, it is anticipated that large, 50-to-60-meter span chambers will be excavated to house neutrino detectors. These activities present near-term and long-term opportunities to address long-standing geoscience and geoengineering questions about the mechanical and hydrologic response of rock masses at spatial scales ranging from centimeters to hundreds of meters and temporal scales ranging from milliseconds to decades. The objectives of this research are to (1) Advance the understanding of rock deformation over multiple scales of length and time and (2) Advance the technology of characterizing rock deformation. In addition, we see this project contributing to testing the hypothesis that critically-stressed fractures are hydraulically conducting over the range of scales of fractures found within the former mine. The work will also show how deformation relates to rock-mass characteristics. Our research effort is a collaborative partnership among three U.S. universities, the University of Tokyo, the Japan Atomic Energy Agency, and private companies. The U.S. team will deploy current state-of-the-art deformation monitoring technologies based on Fiber Bragg Grating (FBG) and Distributed Strain and Temperature (DST) fiber-optic sensors at SUSEL. The FBG and DST sensors will be installed at the 4100-ft and 4850-ft levels in rooms and drifts adjacent to planned physics laboratories. The sensors will provide measurements at the meter scale over a region spanning several hundred meters. An array of tiltmeters will also be deployed at the 2000-ft, 4100-ft, and 4850-ft depth levels to provide deformation measurements, which are sensitive to solid-earth tides, over length scales between 10 and 100 meters. Temperature-sensing fiber will be placed in the water in the No. 6 Winze down to 8000-ft depth, in shorter-length boreholes, and along drift walls to monitor water inflows. In complementary research the Japanese team will deploy fiber-optic monitoring arrays at an underground vault in Aburatsubo and deep underground laboratories in Horonobe and Mizunami. They will also refine FBG deformation monitoring technology to improve resolution by one to two orders of magnitude.UBroader Impacts: (1) The U.S. research team will gain international perspective and knowledge. Graduate students from Wisconsin, South Carolina, and Montana will be trained in multi-institutional, multidisciplinary research. (2) The training of students and teachers at the high school and college level in the EPSCoR (Experimental Program to Stimulate Competitive Research) states of Montana and South Dakota will be enhanced. (3) Multidisciplinary connections will accelerate the development of fiber-optic techniques for structural health monitoring. (4) The prototype fiber-optic sensor network will provide firsthand operational information about its capabilities to personnel at SUSEL. The methodology and research data will contribute to the design, construction, and safe operation of DUSEL.