Control Survey Automation for Complex Microtunnelling

Abstract

Control Survey Automation for Complex Microtunnelling Microtunnelling projects with complex Design Tunnel Alignment demand a quality Navigation System to ensure the Tunnel Boring Machine may excavate the planned route within tolerance. Industry standard utilises a Gyroscope or Total Station Navigation System. As the complete pipe string advances the Microtunnelling Navigation System must carry out measurement and calculation routines on the go. This results in minor inaccuracies which compound with increasing length of tunnel. It is therefore essential to calibrate the Navigation System at regular intervals. This is traditionally achieved by manual control measurements, carried out when tunnelling is at standstill. The associated downtime in excavation production is directly reflected in project costs. A supplementary system that interfaces directly with Navigation Systems can significantly reduce the need for manual control measurements and associated downtime. One method is the “MultiStation” system, where a sequence of Total Stations establish a connection between the Tunnel Boring Machine and launch shaft. MultiStation automates a control measurement within minutes, reducing reliance on manual Survey. Small pipe diameters (<1400mm) and Direct Pipe may have insufficient space to install a Total Station. This is solved by combination of Gyroscope Navigation and “TUnIS.pipelight”, a supplementary system where sensors are optimized for compactness and robustness in small pipe diameters. TUnIS.pipelight creates a geometric connection between the TBM and survey network in the launch shaft. Innovative sensors, compact in form and function, determine intersecting angles by cameras observing LED spots. MultiStation System When excavating a utility tunnel using microtunnelling, pipe jacking or direct pipe methods, the complete tunnel structure or pipe string is often in motion during the construction phase. Complex, long-distance and curved tunnelling may preclude simple navigation via pipe laser from the launch shaft. Industry standard demands a navigation system provide the TBM position using either Gyroscope with Hydrostatic Water Level combination, or a laser Total Station. Measurements required to determine the machine position are 1 No-Dig Down Under 2023 Control Survey Automation for Complex Microtunnelling Jürgen Göckel and Matt Jarvis carried out in parallel with tunnelling, i.e. measurements do not take place at standstill, but while the pipe string is in motion. Figure 1. Industry Standard Navigation System with Laser Total Station Since these systems do not refer to a fixed reference outside the pipe string, inaccuracies arise with each measurement, which compound as tunnel length increases. To calibrate these Navigation Systems, manual control measurements must be carried out at regular intervals by a Surveyor, which require a standstill of tunnelling production. MultiStation System aims to automate manual control measurements and integrate within the standard workflow of Navigation Systems. Since a MultiStation System alone does not guarantee a permanent update of the TBM position, the system is designed as an extension to the industry standard Navigation Systems based on Gyroscope or Laser Total Station. An automated control measurement is completed in under two minutes and may be carried out frequently with little impact on production. MultiStation System significantly reduces downtime caused by manual surveying and the precise position of the tunnelling machine is available at all times. The cost of the system should be compensated through higher tunnelling productivity. In addition, the risk of increased jacking loads due to several hours downtime for manual control measurement on longer tunnelling drives is reduced. Concept MultiStation System begins with one Total Station designed as a fixed point in the launch shaft. The system is extended into the tunnel via a chain of Total Stations which maintain Line of Sight to each other. From the launch shaft, an automatic traverse measurement is executed in sequence through the complete pipe string. As a result, the Navigation System installed close to the TBM is calibrated with accurate coordinates. 2 No-Dig Down Under 2023 Control Survey Automation for Complex Microtunnelling Jürgen Göckel and Matt Jarvis

Techniques