Leveling vs. InSAR in urban underground construction monitoring: Pros and cons. Case of la sagrera railway station (Barcelona, Spain)

Abstract

Monitoring is required when dewatering underground construction sites to anticipate unexpected events and preserve nearby existing structures and/or buildings. The most accurate and widespread monitoring method to measure displacements is leveling, a point-like surveying technique that typically allows for tens of discrete in situ sub-millimeter measures per squared kilometer. Another emerging technique for mapping soil deformation is the interferometric synthetic aperture radar (InSAR) method, which is based on SAR images acquired from orbiting satellites. This remote sensing technique can provide better spatial point density than leveling, more extensive spatial coverage and lower-cost acquisitions. This paper analyses, compares and discusses leveling and advanced multi-temporal InSAR measurements when they are used to measure the soil deformation induced by the dewatering associated with underground constructions in urban areas. This comparison, which has not been considered in previous works, is of paramount importance to ascertain the most suitable technique (or combination of techniques) in these contexts. To do so, an experiment was performed in the future railway station of La Sagrera, Barcelona (Spain), in which leveling and advanced multi-temporal InSAR were used to quantify ground deformation by dewatering. The results showed that soil displacements measured by leveling and InSAR were not always consistent. In the context of soil deformation measurements produced by dewatering in urban areas, InSAR measurements appear to be more accurate for investigating soil deformation, whereas leveling was more appropriate for quantifying the real impact on the nearby buildings.

Research on the Design and Automatic Recognition Algorithm of Subsidence Marks for Close-Range Photogrammetry

“…Canny edge detection is a multi-level detection algorithm whose basic idea is to find the position where the gray level change is the strongest in the image. The derivatives of the horizontal and vertical directions are calculated using Canny operator and the gradient and direction of the edge can be calculated, as shown in Formulas (4) and (5). When the gradient and direction are calculated, every pixel on the image is traversed and the point with the biggest gradient among the points with the same direction is reserved, which is the boundary point [24].…”

“…But when in use, facilities like high-speed rail lines are difficult to approach, making leveling using manual measurements unsuitable in many instances. Furthermore, continuous manual infrastructure monitoring is time consuming and cannot meet the demanding requirements imposed by the pace of development [5]. Hydrostatic leveling overcomes the limitations of manual leveling and the instruments are buried in a structure to measure changes in height, A novel monitoring system using innovative fiber-optic liquid-level transducers is proposed for continuously monitoring the settlement of geotechnical infrastructures and its relative measurement error is within 4% [6].…”

Retrospective InSAR Analysis of East London during the Construction of the Lee Tunnel

“…Although much of the Lee Tunnel construction coincided with that of Crossrail, it remained largely unreported because it is much deeper and narrower, so that the surface deformation associated with it is much less apparent than Crossrail's settlement trough. Beyond the UK, InSAR has notably been used to monitor tunnelling projects in China [12][13][14], France [15], Germany [16], Italy [17], Netherlands [18], Romania [19], Spain [20,21] and USA [22].…”

PSInSAR remote sensing observations of deformation behaviour at Salisbury Plain, UK.

“…DInSAR and similar techniques have long been used for mapping large-scale deformation and generating DEMs (Osmanoğlu et al, 2016), aided by high spatial coverage and hence cost-effectiveness as compared to ground investigations. Recent advances have allowed DInSAR to be applied in infrastructure and construction monitoring, and for the location and characterisation of faults (Serrano-Juan et al, 2017;Bonì et al, 2016;Mason et al, 2015).…”