Geological Models for Infrastructure Design:

Transcription

1 Geological Models for Infrastructure Design: Reducing Geotechnical Risk and Supporting Sustainability Alan Keith Turner Emeritus Professor of Geological Engineering CSM Visiting Research Associate - British Geological Survey June 16, 2018 Three-Dimensional Geological Mapping Workshop Resources for Future Generations Vancouver, BC, CANADA

2 SUMMARY 3-D Geological Modeling Concepts Two Recent United Kingdom Infrastucture Applications The Future of 3-D Models for Urban Infrastructure Planning 3-D models for Sustainable Groundwater Resources

3 3-D Geological Modeling Research Began over 3 Decades Ago Evolution of 3-D geological modeling: Can we do it? Initial fundamental research, early software and hardware limitations How do we do it? Implementation of workflows, databases, software matures Why are we doing it? Operational within geological surveys, models now becoming accepted by users. The 3-D modeling process has become increasingly demand-side driven

4 3-D Geological Model Data Sources Legacy Subsurface Explorations Digital Terrain Model Standardized Stratigraphic Sequence Legacy Geological Maps & Reports Project Boreholes Test Pits & Trenches New Field Mapping & Observations Interpretive Cross-sections 3-D Model Geophysical Surveys

5 3-D Framework Models May Contain Different Levels of Detail, depending on Scale and Data Sources Simple, Generalized Model Moderately Detailed Model Highly Detailed Model Heinenoord Tunnel Hack, et al., 2006

6 BGS Produces Models at Many Scales National 3-D UK Model Regional 3-D Model (London) Site 3-D Model (Farringdon Station)

7 Models may be Nested from Regional to Local Scales

8 Two Recent UK Infrastucture Applications 1. Farringdon Station for London CrossRail Project ( ) 2. Planning for Electrification of Railway between Leeds and York (2015)

9 Farringdon Crossrail Station in Central London Intense Urban Setting Complex Fault Pattern

10 London CrossRail Modeling ( ) Crossrail will link Reading and Heathrow in the west with Shenfield and Abbey Wood in the east via 21 km (13 miles) of twin-bore tunnels under central London Connects with key London rail stations and London Tube network Passes around and beneath existing Tube tunnels at depths up to 30 m (100 ft) thus encountering some problematic geological conditions Crossrail Crossrail will bring 1.5 million more people within 45 minutes of central London. When it opens fully in 2019, Crossrail will increase London's rail transport capacity by 10%

11 Farringdon Station Two 300 m (985 ft) platform tunnels plus multiple access tunnels 30 m (100 ft) below the surface Crossrail Architect s Impression of Farringdon Platform Crossrail PRIOR INVESTIGATIONS IDENTIFIED ADVERSE GROUND CONDITIONS: Multiple faults, Buried valley of Fleet River Water-bearing sands within the tunneling medium (Lambeth Group) Potential surface settlement on old buildings and surface railway

12 Existing 3-D Subsurface Information BGS Regional 3-D London Model Oblique View of Completed London Model (From Mathers et al., 2014)

13 Initial 3-D Geological Model of Farringdon Station Site By 2008 Crossrail had completed initial ground investigations, at least one fault was identified but little confidence in the ground model. In 2009 Crossrail commissioned BGS to develop a 3-D geological site model to guide future investigations This model was constructed using existing London regional model, historical & third-party data, and available Crossrail data

14 Farringdon Crossrail Station Location Map 7 faults identified (green shadings = uncertainty envelopes)

15 3-D Oblique View of 2009 Model

16 Farringdon Station Design Modeling ( ) Initial 2009 BGS 3D geological model of Farringdon station was progressively updated as new Crossrail exploration data received

17 3-D Oblique View of Boreholes

18 Farringdon Station 3-D Model 3-D model display of sand and gravel (water-bearing) units and faults (Aldiss et al., 2012)

19 Farringdon Station 3-D Model Integrated into Site Supervision Workflow ( ) In 2013, this model was handed over to the contractor and integrated into the site supervision workflow (Modified from Cabrero & Gakis, 2014)

20 Model updated on daily basis as station excavated - Faces mapped as excavation advanced - (Modified from Cabrero & Gakis, 2014)

21 Model updated on daily basis as station excavated - Digital face maps updated 3D model - (Modified from Cabrero & Gakis, 2014)

22 Farringdon Crossrail Station 3-D View of Geological Sections in Final Model

23 Farringdon Station Predicted vs Observed locations of sand lenses and faults (Gakis, 2014)

24 Farringdon Station Success in Predicting Geological Conditions Geological predictions at one section of Farringdon station (Gakis, 2014)

25 Farringdon Station Comparison of Estimated Risks to Tunneling from Water-Charged Sand Units (Gakis et al., 2014)

26 Consequences of Employing Farringdon Station 3D Model Because the Ground Model was updated daily as station excavated: Enabled geological predictions ahead of excavation Provided a geological database to collate and store all acquired data Confidence increased as tunneling progressed Key Element in reducing Geotechnical Risk 70% reduction of in-tunnel probing compared to original plan Efficient SCL design and installation Station excavation completed 3 months early!

27 Planning for Electrification of Railway between Leeds and York (2015) 28 km (17.5 miles) existing railway line is planned for electrification. Concern for foundations of support masts Depth to bedrock, type of rock, weathering Old mine workings, karst features, fault structures Long narrow 3-D model created along railway 28 km long; 80 m wide, 30 m deep Outputs transferrable to Bentley Microstation BGS completed/delivered model in 1 month

28 Planning for Electrification of Railway between Leeds and York (2015) 4-km long section of central portion of route Model consists of 3 parallel sections, and numerous short rung sections (25 shown in this portion of route) Model based on 1:10,000 BGS maps and 102 borehole logs Model contains 57 geological units, 11 coal seams, 29 faults

29 Planning for Electrification of Railway between Leeds and York (2015) Isometric view of 3-D model (central 4 km section)

30 Planning for Electrification of Railway between Leeds and York (2015) Center-line Cross-section of 3-D model (central 4 km section) showing faults

31 How Did Client Use the Model? Combined geological model information with CAD infrastructure design files This illustrates the future of 3-D model applications

32 3-D Geological Model for Railway Electrification between Leeds and York

33 PDF-documentation of a bridge reconstruction site PDF combines terrain and digital CAD-based ground model with geological model provided by the BGS.

34 Design for a proposed sheet pile wall showing existing ground surface and CPT Cone Penetration Test colors define subsurface materials: Red - coarse grained made ground; Yellow - alluvium; Orange - river terrace deposits (sand and gravel)

35 The Future of 3-D Models for Urban Infrastructure Planning City of London on 3-D Geology Model City model courtesy of ARUP

36 Building Information Modeling (BIM) But Where is the Geology? Courtesy Mott Macdonald Process involving the generation and management of digital representations of physical and functional characteristics of places BIM files can be exchanged or networked to support decision-making about a place. Used by individuals, businesses and government agencies who plan, design, construct, operate and maintain diverse physical infrastructures.

37 Geotech-BIM BIM and the Subsurface Grice & Kessler, 2015 Extend/Integrate 3-D Geological Modeling techniques to the BIM environment

38 Silvertown Tunnel East London A New Road Tunnel under the Thames Extensive ground investigation 3-D model developed in CAD Integrated geology and infrastructure GeoTech BIM

39 Silvertown Tunnel East London A New Road Tunnel under the Thames Extensive ground investigation 3-D model developed in CAD Integrated geology and infrastructure GeoTech BIM

40 Silvertown Tunnel East London A New Road Tunnel under the Thames Extensive ground investigation 3-D model developed in CAD Integrated geology and infrastructure GeoTech BIM

41 Silvertown Tunnel East London A New Road Tunnel under the Thames Extensive ground investigation 3-D model developed in CAD Integrated geology and infrastructure GeoTech BIM

42 Sustainable Development of Groundwater The Environment Agency is the environmental regulator in England and Wales: Responsible for protecting and improving the environment and promoting sustainable development. Manages groundwater resources to maintain & improve quality of drinking-water supplies and reduce flooding risks.

43 Sustainable Development of Groundwater In 2009, the BGS developed a 3-D geological model of East Yorkshire EA comment: The 3-D geological model has helped the development of a much better conceptual model of the aquifer between Hull and Flamborough Head, which has in turn helped us to develop our groundwater management strategy.

44 Sustainable Development of Groundwater A recent BGS 3-D model of the Vale of York in northern England supported regional evaluations of the Triassic Sherwood Sandstone Group aquifer which underlies heterogeneous glacial deposits. Higher-resolution site-specific models, based on this regional model, are being prepared for use by water-supply companies to understand potential pathways of nitrate pollution.

45 Groundwater Modeling in Chalk Aquifers From concept to reality Conceptual model of the groundwater system in the chalk Numerical simulation of high and low water table in geological framework

46 Extent of Chalk Aquifer Model in south-east England. Dots show borehole control points. (Woods et al. 2015)

47 National 3-D Model Attributed to show Chalk Aquifer Classificarion (Mathers et al., 2014)

48 Prediction of Aquifer Response near London (Cripps & Kehinde, in press)

49 Prediction of Aquifer Response near London (Cripps & Kehinde, in press)

50 Prediction of Aquifer Response near London 3-D Model shows Chalk and Lower Greensand Aquifers (Cripps & Kehinde, in press)

51 Prediction of Aquifer Response near London Response of Chalk and Lower Greensand Aquifers NW SE (Cripps & Kehinde, in press)

52 Prediction of Aquifer Response near London Response of Chalk and Lower Greensand Aquifers NW SE (Cripps & Kehinde, in press)

53 Prediction of Aquifer Response near London Response of Chalk and Lower Greensand Aquifers NW SE (Cripps & Kehinde, in press)

54 Thames Integrated Model An example of the importance to society of integrating the data, information, and knowledge within the 3-D modeling and analysis process. Links the detailed geology of the Thames catchment with groundwater and surface water hydrology to understand the interactions between rainfall, evaporation, and runoff. Two Major Aquifer Systems 1. Jurassic limestones of the Cotswolds in the West. 2. Chalk aquifer in the East

55 Thames Integrated Model Chalk & limestone groundwater models, river model, and recharge model linked at run-time to an abstraction management model using OpenMI.

56 Questions