Monitoring and Deformation Analysis of Groynes Using TLS at the River Elbe

Abstract

To enter the Port of Hamburg, one of Europe’s busiest ports all vessels need to navigate around 145 km along the Elbe river, a tide influenced navigation channel. To protect the Elbe shoreline from erosion and to channel the waterway groynes (rigid hydraulic structures) have been built along the river. In the past years since ca. 2001 there has been a large increase in damage of groynes structural integrity at parts of the German waterways. The reason for this was determined in the ever growing size of container vessels passing by and inducing long periodical primary waves which have such a force that they erode the groynes rock structure. To analyse and improve the groynes structural resistance for vessel-induced long periodical wave loads an in-situ study is carried out at Juelssand, located at the Elbe river estuary. Over a period of two years the change of the geometrical structure of two different groyne shapes is monitored automatically by utilising two terrestrial laser scanners mounted in protective housings, located each on a 12 m high platform. The self-contained monitoring systems perform scanning of the two groynes one to two times a day at low tide, as the structures are fully submerged at high tide. The long-periodical wave loads are also determined using pressure sensors in each groyne. To correlate the captured data with vessel events and analyse the effects, vessel related parameters are recorded utilizing the Automatic Identification System (AIS). <br><br> This paper describes the automated processes for the data acquisition and focusses on the deformation that is calculated using current, extended and new algorithms of the Point Cloud Library. It shows the process chain from the acquisition of raw scan files from an elevated station to the filtering of point cloud, the registration, the calculation of pointwise changes and the aggregation to a grid for later correlation with ship parameters. When working outdoor in all kinds of weather conditions, the processes and equipment need to be robust and account for various cases and situations. This is especially applicable for the algorithms, which need to be adaptable to different scenarios like wet surfaces or snow and unwelcome objects ranging from flotsam to birds sitting on the groyne. At the current stage of the research, deformation in the magnitude of a couple of decimetres is observable. The orientation and location of the deformation is on the seaward side and corresponds to the lower distance of vessels leaving the harbour.

Structural health monitoring of inland navigation structures and ports: a review on developments and challenges

“…TLSs and LiDAR are widely used to create high-resolution 3D digital elevation models of river and coastal banks to monitor spatial and temporal morphological changes. 107,127 Tschirschwitz et al 213 monitored groynes on a navigation channel from the Elbe to the Port of Hamburg, Germany. There were cases of breakthroughs between connections between revetments and groynes in the channel.…”

Accurate Measurement of the Riverbed Model for Deformation Analysis using Laser Scanning Technology

“…Besides the shifts and deformations of the buildings and constructions displacements of natural formations like hillsides (landslides) [1,19] are also measured. There are often used methods based on terrestrial 3D scanning [10,8,5], airborne 3D scanning [14], combination of both [21], or in combination with other instrument's measurement as ground penetrating radar [3].…”

“…Standpoints (Scan1-Scan12) and control points (1-22) configuration for 3D laser scanning. Control points1,2,11,12,21, 22 are identical to K1 -K6 fast normal computation in the following steps. The most suitable format is "btx" which is a binary format for ordered points.The second used software was Geomagic Studio.…”