Field Testing and Monitoring of an Experimental Soil-Bentonite Cutoff Wall

土-膨润土泥浆防渗墙被广泛应用于防渗、堤防修复、污染物控制等领域。它们在这些关键应用中的广泛使用需要更好地了解它们的建成状况和长期行为。考虑到竣工状态，防渗墙的就地渗透性受缺陷的存在和墙体内部应力的影响很大。传统的施工质量控制程序不足以在整个安装过程中验证回填材料的均匀性，而且还没有商业技术可用于非破坏性地检测缺陷或验证是否存在缺陷。关于长期行为，有几个因素可能会导致墙体渗透性随时间的变化，包括应力和干湿循环的变化。该项目旨在通过设计、施工、现场测试和监测将在巴克内尔大学校园附近安装的全仪表防渗墙，来解决防渗墙的短期(建成)和长期完整性方面的问题。从我们的水坝、堤坝和污染物控制系统中更好地了解和表现，以及通过本科生和研究生参与研究、作为年度工程夏令营的一部分向中学生宣传、向学生和从业人员展示防渗墙的最新技术/实践，以及通过正式的研讨会演示来更好地了解和表现我们的大坝、堤坝和污染物控制系统，以及大量的教学、培训和指导，社会将受益。防渗墙将作为时间和位置的函数被完全用于监测回填土中的现场状况(例如，3D应力状态、垂直和横向变形以及孔隙水压力)。将研究电阻成像，以定位在已知位置和已知大小的墙内放置的缺陷，目标是开发一种可行的地球物理方法来检测SB墙中的缺陷。监测将辅之以实验室测试和现场测试(例如，锥体渗透、叶片剪切、膨胀计和标准渗透测试)，随着时间的推移，还将执行这些测试，以揭示随时间变化的行为。最后，对SB防渗墙内的应力分布进行了数值模拟，并将结果与现场实测应力进行了比较。所有实地和实验室数据都将在一个地理空间信息系统框架内进行管理，该系统将通过网络向公众开放。

Soil-bentonite slurry trench cutoff walls are widely used for seepage control, levee repair, and pollutant containment. Their widespread use in these critical applications requires a better understanding of their as-built condition and long-term behavior. Regarding the as-built condition, the in-place permeability of cutoff walls is heavily influenced by the presence of defects and by the stress within the wall. Conventional construction quality control programs are insufficient to verify backfill homogeneity throughout the installation, and commercial technologies are not yet available for non-destructively detecting defects or verifying the absence of defects. Regarding long-term behavior, several factors may cause changes in permeability of the wall over time including changes in stress and wet-dry cycling. This project seeks to address these questions regarding both the short-term (as-built) and long-term integrity of cutoff walls through the design, construction, in-situ testing, and monitoring of a fully instrumented cutoff wall to be installed near the Bucknell University campus. Society will benefit from better understanding and performance from our dams, levees and pollutant containment systems and from substantial teaching, training, and mentoring through the involvement of undergraduate and graduate students in the research, outreach to secondary students as part of the annual engineering summer camp, and exposure of students and practitioners to the state of the art/practice for cutoff walls via formal seminar presentations.The cutoff wall will be fully instrumented to monitor in-situ conditions in the backfill (e.g., 3D state of stress, vertical and lateral deformations, and pore water pressures) as a function of time and location. Electrical resistance imaging will be investigated for locating defects placed within the wall at known locations and of known size, with the goal of developing a viable geophysical methodology for defect detection in SB walls. The monitoring will be complemented with lab tests and in-situ tests (e.g., cone penetration, vane shear, dilatometer, and standard penetration tests), also performed over time to reveal time-dependent behavior. Finally, numerical model simulations to predict the stress distribution within an SB cutoff wall will be performed and the results compared with the measured field stresses. All field and lab data will be managed within a geospatial information system framework that will be made accessible to the public via the web.