Long-term health monitoring of levee cutoff wall under Garden Highway in Sacramento by distributed fiber optic sensing (DFOS) technology

USACE (US Army Corps of Engineers) is currently implementing a levee improvement project along the American River in Natomas, California. The main  measure for the levee is a Slag Cement-Cement-Bentonite (SCCB) cutoff wall with an objective to reduce potential for seepage induced distress such as backward erosion piping (BEP) and slope instability. The levee cutoff wall is constructed by a mixture of cement, bentonite and slag, which is a low permeability and high strength material. However, these cutoff walls may potentially exhibit brittle behavior in case of excessive loading or deformations. The behavior of these walls during and after an extreme loading conditions need to be monitored to evaluate long term performance of these mitigation measures and also to evaluate reliability of these SCCB cutoff walls. With support from the National Science Foundation and USACE (led by Dr. Khaled Chowdhury), the research team (Ruonan Ou, Andrew Yeskoo, Linqing Luo, John Murphy, Yaobin Yang) embedded optical fiber sensors into the SCCB (Slug cement bentonite) cutoff wall at Natomas Reach I during its construction in July 2020. The curing process of the SCCB slurry was monitored continuously during the first seven days after the SCCB wall construction. Weekly reading is currently taken to measure the final stage of the heat dissipation and the strain development. The monitoring will continue for years to evaluate the performance of the SCCB wall during and after construction, operation and possible flooding and earthquake events.

FO cable installation

 FO cable pretension

 FO cable inside SCCB wall