Geotechnical asset management for improved highway resilience in Alaska

Transcription

1 Geotechnical asset management for improved highway resilience in Alaska, Consultant Mark Vessely, Shannon & Wilson Darren Beckstrand, Landslide Technology, Inc. David Stanley, D A Stanley Consulting Barry Benko, Alaska Department of Transportation and Public Facilities 1

2 The problem Retreating permafrost Embankments previously on frozen ground now settling and deforming Previously frozen soil cuts now liquefying and flowing onto roads Increasing freeze/thaw and water infiltration Rocks dislodged from slopes Pressure on retaining walls Activation of drainages Water-induced debris flows Washouts of bridges and culverts 2

3 What s a geotechnical asset? Rock slope in fair condition, South Tongass Highway. Rocks are occasionally able to reach the road and cause a safety hazard. 3

4 What s a geotechnical asset? Embankment in Poor condition, Sterling Highway. Movement is relatively rapid, necessitating frequent maintenance to keep the road passable. 4

5 What s a geotechnical asset? Retaining wall in Poor condition, Seward Highway. The wall is bowed outward, causing deformation of the guardrail and pavement. 5

6 Alaska s geotechnical asset inventory Rock slopes $ 3.9 billion Good 27% Soil slopes $ 14.4 billion Good 22% Fair 47% Retaining walls $ 0.7 billion Good 73% Total reconstruction value is >3 times that of the state s bridge inventory! Fair 65% Poor 8% Poor 31% Fair 23% 4% 6

7 Asset management process Goals and policies Asset inventory Condition assessment and performance modeling Alternatives evaluation and program optimization Short and long-range plans, programs, and targets Program implementation Performance monitoring and feedback Forecasting models Budget, resource allocation Similar to the MAP-21 process for pavements and bridges Meant to be included in state TAM Plan 7

8 Condition assessment Good: Identified defects, if any, are minor and do not require corrective action. Asset performance and life cycle cost are not adversely impacted by condition. Fair: Significant deterioration has been identified. Corrective action is feasible and would extend the service life and/or improve the performance of the asset. Poor: Deterioration is advanced. Significant mitigation, repairs, or rehabilitation are needed to restore full functionality. Rock slopes: Catchment effectiveness, geology, hydrology, speed, sight distance Soil slopes: Evidence of movement, soil and permafrost characteristics Retaining walls: Wall alignment, corrosion, spalling, drainage Periodic assessment by trained inspectors 8

9 Life cycle cost Life extension of a soil slope using a preservation strategy Department goal to minimize life cycle cost Quantitative models of deterioration, cost, and effectiveness 9

10 Risk management Risk measured in dollars, likelihood consequence of service disruption Likelihood is estimated based on condition, as a proxy for resilience Consequence depends on ADT, detour distance, using AASHTO Red Book Incorporates safety and mobility goals Goes directly into life cycle cost analysis Dalton Highway washout, April

11 Investment analysis Condition index after 10 years 66 45% 65 40% % 62 30% 61 25% 60 20% 59 15% % 56 5% 55 0% Initial 2015 funding ($M) Percent Good or Poor Analysis quantifies bangfor-the-buck, funding vs performance Supports the development of condition targets At $150 M/year, target 27% Good, 34% Poor 11

12 Next steps Alaska performance mapping system Policy support for TAM process Budgeting, work tracking improvements Preservation and mitigation STIP projects Public tracking of performance vs targets Asset-level risk and life cycle cost analysis for priority setting and programming (geotechnical asset management system) Minnesota bridge risk-based planning system All Other Scaled Bridge Programming Index (BPI) values Structure condition Fracture Overw t Overht Vehicle Over BPI Deck Superstr Substruc Scour Critical Fatigue trucks trucks crashes topping score brkey rdeck rsuper rsubs rscour rfraccrit rfatigue roverwt roverht rcrashes rovertop rscore D C

13 Thank you! 13