Session 3.1
Reality Capture Challenges in Tunnels – WestConnex M4 East Case Study
Synopsis:
This presentation describes the challenges faces in the capture and processing of the Reality Capture project which was conducted prior to the opening of the WestConnex M4 East Tunnel. The project aimed to capture a baseline understanding of the conditions of the tunnel at opening and to increase the effectiveness of maintenance of the asset into the future using geospatial data.
Learning Objectives:
1. Explore the key challenges of Reality Capture in tunnel environments
2. Understand the importance of geospatial data for infrastructure projects
3. Understand the benefits of high resolution imagery in determining conditions of tunnels
Body:
Planning and execution of large tunnel infrastructure projects is complex especially due to the constrained nature of underground environments. This limits the time and the ability to capture meaningful data. Contractors traversing the project site always, ongoing commissioning works, clients that push for handovers in the shortest time possible all these factors and more drive innovation in how we collect, process and analyse critical geospatial data.
Land Surveys and Dibit (Austrian specialist tunnelling company) have brought custom built hardware and software solutions to the Australian market to capture high resolution georeferenced 3D models of tunnels during construction and throughout the O&M phases of the project lifecycle. This data and the analysis tools associated allow for virtual inspections and managements of defects from the moment the tunnel is excavated throughout the construction process through to the end of the asset life.
These applications include:
– Mapping the condition of shotcrete, segments, pavement and other tunnel elements to build a cohesive database of items and information. Cracks in concrete, leakage, mineral precipitation, staining can be mapped down to millimetre precision to provide a clear understanding of severity, effect and position of defects.
– Comparison of various epochs of capture to determine the effect of time in a tunnel environment thereby providing objective repetitive geospatial data for aiding in determination of defect causes.
– Critical data that can be used in predictive analysis and can help manage the maintenance of an operating tunnel asset over decades.
Capturing the new M4 East Tunnel prior to its opening to the public in July 2019 allowed us to create a baseline dataset of the tunnel for the operator to understand the condition of the asset at the commencement of its life. This endeavour occurred between handover and of the tunnel from the design and construct contractor to the asset owner and the official opening to the public.
The capture and processing of a project of this nature has not been without its challenges, these include:
– Navigating the commissioning phase of the project and working in unison with commissioning work many false starts were made due to other scheduled work (e.g. testing of deluge systems and electrical isolations)
– Access to install survey control into the tunnel up to 100 other workers and their equipment present posing line of sight challenges
– Short time frames data was captured over 4 shifts which would usually take 6+ shifts to conduct.
– Mobile Laser Scanning (MLS) noise with MLS data capture being a line of sight endeavour the intent is to have a clear run at all the tunnels in a single mobilisation. This was only possible on the final night of capture
– High volume of data to process data capture totalled over 500GB of raw point cloud data and 50,000 high resolution photographs. Transferring and working with this size of data requires consideration in IT infrastructure.
– Delivering a dataset that can be handles by with limited computing power data structure and delivery mechanism challenges allowing our client to easily use the data.