The application of distributed optical fiber sensors (BOTDA) to sinkhole monitoring. Review and the case of a damaging sinkhole in the Ebro Valley evaporite karst (NE Spain)

Gutiérrez, Francisco (Universidad de Zaragoza) ; Sevil, Jorge (Universidad de Zaragoza) ; Sevillano, Pascual (Universidad de Zaragoza) ; Preciado-Garbayo, Javier ; Martínez, Juan J. ; Martín-López, Sonia ; González-Herráez, Miguel

Resumen: Distributed optical fiber sensors (DOFS) have been postulated as a suitable technique for long-range monitoring of sinkhole-related subsidence, and possibly for the anticipation of catastrophic collapse (early-warning systems). The strain data published in previous works refer to artificial experiments considering real and virtual cover collapse sinkholes characterized by rapid subsidence and sharp lateral deformation gradients. The influence of the subsidence mechanism (sagging, collapse, suffosion) on the capability of DOFS to satisfactorily detect active subsidence is discussed. Sagging sinkholes with poorly-defined lateral edges, low lateral deformation gradients and slow subsidence are identified as the most challenging scenario. The performance of BOTDA optical fiber for monitoring such type of sagging sinkholes is evaluated in the active Alcalá sinkhole, which affects a flood-control dike creating a high-risk and -uncertainty scenario. This sinkhole shows active subsidence in sections tens of meters long with maximum subsidence rates ranging between 5 and 35 mm/yr. The comparison of vertical displacement data measured by high-precision leveling and the strain recorded by two types of fiber optic cables shows good spatial and temporal correlation. The subsidence sections are captured in the strain profiles by: (1) troughs of negative strain (contraction) in the area affected by subsidence, with the maximum strain associated with the point of most rapid settlement; and (2) lateral ridges of positive values (extension) in the marginal zones. A subsidence acceleration phase associated with a flood is also captured by substantial increments in the strain values. In this challenging scenario, despite the reasonably good spatial and temporal correlation between the displacement and strain data, the unambiguous identification of the active subsidence area with the fiber optic data alone might be difficult. Better results could be obtained improving the monitoring system (e.g., tighter cable-ground coupling) and testing other types of sinkholes with more localized deformation zones and higher subsidence rates.

Idioma: Inglés

DOI: 10.1016/j.enggeo.2023.107289

Año: 2023

Publicado en: Engineering Geology 325 (2023), 107289 [13 pp.]
ISSN: 0013-7952

Financiación: info:eu-repo/grantAgreement/ES/AEI/PID2021-123189NB-I00
Financiación: info:eu-repo/grantAgreement/ES/DGA/T20-20R
Financiación: info:eu-repo/grantAgreement/ES/MICINN/PRE2018-084240
Financiación: info:eu-repo/grantAgreement/ES/MINECO/CGL2017-85045-P
Financiación: info:eu-repo/grantAgreement/ES/MINECO/DI-17-09169

Tipo y forma: Artículo (Versión definitiva)

Área (Departamento): Área Física Aplicada (Dpto. Física Aplicada)
Área (Departamento): Área Geodinámica Externa (Dpto. Ciencias de la Tierra)