Observed Performance and Analysis of SEM Cavern Construction in Downtown Los Angeles

Zheng, Haotian; Bragard, Christophe; Calvo, Carlos Herranz; Mooney, Michael A.; Gutierrez, Marte

doi:10.1061/(asce)gt.1943-5606.0002639

Cited by 6 publications

(2 citation statements)

References 21 publications

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“…This monitoring system captured an increase in surface subsidence coincident with the crossover cavern excavation. Between June 2018 and February 2019, a vertical settlement magnitude of 1.8 cm was measured along 2nd Street directly above the cavern by GSSP (Figure 2), with peak deformation rates exceeding 2.5 cm/yr [72]. Subsidence rates measured in this location during 2018-2019 are much higher than regional subsidence rates typically found in southern California due to anthropogenic activities, including groundwater pumping and oil extraction [24,73].…”

Section: Study Areamentioning

confidence: 86%

“…Sequential excavation of the crossover cavern took place from 30 May 2018 to 14 March 2019, after which 30 and 46 cm liners of shotcrete and concrete, respectively, were installed. Sequential excavation follows principles of the observational method, requiring a complex monitoring system with extensive instrumentation, including a network of GSSPs and automated total stations capable of making settlement measurements with an accuracy of ±0.7 mm [72]. This monitoring system captured an increase in surface subsidence coincident with the crossover cavern excavation.…”

Section: Study Areamentioning

confidence: 99%

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Mapping Urban Excavation Induced Deformation in 3D via Multiplatform InSAR Time-Series

2021

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Excavation of a subway station and rail crossover cavern in downtown Los Angeles, California, USA, induced over 1.8 cm of surface settlement between June 2018 and February 2019 as measured by a ground-based monitoring system. Point measurements of surface deformation above the excavation were extracted by applying Interferometric Synthetic Aperture Radar (InSAR) time-series analyses to data from multiple sensors with different wavelengths. These sensors include C-band Sentinel-1, X-band COSMO-SkyMed, and L-band Uninhabited Aerial Vehicle SAR (UAVSAR). The InSAR time-series point measurements were interpolated to continuous distribution surfaces, weighted by distance, and entered into the Minimum-Acceleration (MinA) algorithm to calculate 3D displacement values. This dataset, composed of satellite and airborne SAR data from X, C, and L band sensors, revealed previously unidentified deformation surrounding the 2nd Street and Broadway Subway Station and the adjacent rail crossover cavern, with maximum vertical and horizontal deformations reaching 2.5 cm and 1.7 cm, respectively. In addition, the analysis shows that airborne SAR data with alternative viewing geometries to traditional polar-orbiting SAR satellites can be used to constrain horizontal displacements in the North-South direction while maintaining agreement with ground-based data.

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Section: Study Areamentioning

confidence: 86%

Section: Study Areamentioning

confidence: 99%