Pavement Rehabilitation Drainage Renewal or Pavement Rehabilitation Which should come first? William Gray, CPEng Technical Principal (Pavements) Elke Beca, MTech Pav, BE Strategic Asset Management Engineer

Introduction As early as 1820, John McAdam noted that regardless of the thickness of the pavement structure, many roads in Great Britain deteriorated rapidly when the subgrade was saturated

NZTA funded research Analysis tool and associated methodology to plan pavement drainage interventions. The Opus project team acknowledge the support of NZTA, in particular Gordon Hart and Roger Bailey; Luca De Marco (past NZTA project manager); the project Steering Group and Peer Reviewer Dr Ian Greenwood.

Drained or undrained The Repeat Load Triaxial Test (RLT): pore pressure and strain rate changes in undrained state affects basecourse performance

Pavement and land drainage Our project has been focussed on pavement drainage assets

Pavement Drainage Initiatives Prevent moisture entering pavement Waterproof surface and shoulder Longitudinal drains (lined/unlined channels and side drains) Adequate cross slope and longitudinal grades (crossfall and gradient) Manage groundwater effects Subsoils Pavement materials - moisture sensitivity Control fines from production, construction and ageing Minimise moisture in pavement structure Surface is maintained separately and not typically considered under ‘drainage’ Only factors that can be influenced outside of pavement renewal is longitudinal drains

Research Report 555 Optimising Drainage Maintenance for Pavement Performance. (J. Patrick, H. Arampamoorthy, G. Arnold) Exponential relationship between saturation and rate of rut development in granular basecourse Equilibrium saturation ~60% Finite element models show once basecourse infiltrated, can take weeks for water content to return to equilibrium. www.nzta.govt.nz/resources/research/reports/555/index.html Impact of moisture in pavements under loading How long does water stay in a pavement Method for identifying drainage deficient areas in the field

Research Report 555 - Scorecard

Research Report 555 Recommendations Drainage risk score included in RAMM RAMM Drainage condition rating carried out for high risk sections Rut rates monitored as standard process for subsoil deficiency or blockage.

TRB Research Paper LTPP data Rut progression dependant upon The Relationship between Traffic Loading and Environmental Factors to Low Volume Road Deterioration. (Henning, Alabaster, Arnold & Liu (93rd TRB Conf.)) LTPP data Rut progression dependant upon Moisture sensitivity Drainage adequacy ESA docs.trb.org/prp/14-2372.pdf 

Current Research Objective – to develop analysis tool for business case planning Forecast renewal need for drainage and benefits of intervention Investing more in drainage needs and programming drainage works well ahead of resurfacing/renewals will prolong the life of the existing pavement

Activities and Collaboration Develop robust short term plan (FWP – 5yr) Understand long term funding needs Opus Surface Model Empirical – Stochastic – pavement condition data Geosolve Subsurface Model Mechanistic – FWD – pavement performance data Pilot Areas: SH2 Napier to Wairoa, SH 1 Northland and the Western Bay of Plenty network

Day One…………