The March presentation to the British Tunnelling Society describes the application of ‘cloud based data’ to real time review of temporary works performance against design within tunnels, illustrated by a number of example projects in the UK and Hong Kong. Presenters were Angus Maxwell, chief executive of Maxwell Geosystems and Marcos Invernici, standing in for Anmol Bedi, both of Bedi Consulting.
recent years tunnel projects have stated to collect lots of data. The objective behind the data is to achieve greater certainty in construction and, if the processes work effectively, the data can reduce risk and accelerate the works. If the processes are not effective then the data can become an impediment to the works and can increase uncertainty and reduce confidence. To ensure the former systems need to address some of the common issues surrounding data and information, key among them being the tendency for people to operate in silos. The presentation focussed on some new developments in this area and was illustrated by reference to projects in the UK and Asia.
Data Systems as Part of Partnering Arrangements
Adversarial contract terms are not a good starting point for data collaboration but on the 39 km Singapore Power cable tunnels the client took an unusual approach during the tender process requiring the contractors to invest and partner in information sharing at the highest level.
The tunnels were driven using 14 tbm real-time monitoring in Granite rock, mixed face with decomposed soils, meta-sedimentary strata and old alluvium from 19 shafts. They were divided into NS and EW systems with 3 main contracts in each. Geology varied from highly fractured water bearing metasedimentary rocks of the Jurong Formation into Bukit Timah Granite with corestones at rock head, deep weathering layers with overlying fill and peat in places to Old Alluvium with loose fluvial sands and marine muds above in the east.
The tunnels were driven from 18 no. approximately 20m diameter shafts up to 60m deep and constructed using diaphragm walls in 12 panels 3 bites. The bases of the shafts were extended by drill and blast into rock with adits and enlargements. The main drives were driven by TBMs with slurry machines used in rock/mixed face conditions and EPBMs in Old Alluvium. The permanent lining was constructed with 1m and 1.4m rings to allow tight radii to follow road alignments. This required careful segment reinforcement design.
An earlier phase 1 had been difficult with stoppages due to settlement. The Phase 2 tunnels posed many risks including sensitive structures and compressible soils. With the tunnels being deep there was a need for hyperbaric interventions to control inflow. Many of these would be in mixed geology and mixed face including many rock head transitions which had proven to be difficult in previous tunnels. The tunnels were also driven in close proximity to a variety of sensitive assets and the client needed something to increase confidence.
The Northeast Boundary Tunnel (NEBT) is a reinforced concrete sewer tunnel (7m diameter, 15–48m deep), that will increase the capacity of the existing sewer system in Washington DC’s North East District.
Maxwell GeoSystems is providing its industry leading MisssionOS cloud-data platform, to meet the client’s needs for real-time feedback of ground deformation in conjunction with shaft construction & key TBM operation parameters.
Due to the sensitivity of surrounding infrastructure, the client relies on MissionOS ’s real-time alarm notification system to alert key parties of potential unwanted settlements.
Addtional key features implemented on this job include proximity functions to relate ground deformation to TBM operations, prediction models to estimate final settlement, and TBM parameter alarms.
The NEBT is the largest component of the Clean Rivers Project in Washington DC (USA) and will be built using the TBM “Chris” (92m in length).
The tunnelling process control project faces a number of challenges including heavy clay and water bearing clayey sands at water pressures up to 3bar, a challenging alignment with 15 curves, and a complex work environment for shaft construction with small shaft sites combined with urban residential neighbourhoods and a high traffic corridor.
Parties afiliated with the Project: Designer: Brierley Associates; TBM Supplier: Herrenknecht; Slurry Walls, Jet Grout, Secant Piles, Solider Piles: Treviicos; Segmental Tunnel Liner Supplier: ConSeg JV; Muck Hauling: Bulldog; Construction; Instrumentation: Entech; Traffic Engineering & Instrumentation Installation: EBA; Construction Manager: EPC Consultants; DC Clean Rivers Program Manager: McMillan Jacobs and Greeley & Hansen.
Keywords : tunnel excavation monitoring system
For those serious about data as a business resource the Mission Enterprise allows you to define standard operating models for data across all your business globally on the web and stat to build a data resource that can give you significant business advantage.