Pavement design for low volume roads. Guy Doré, ing., Ph.D. NSERC i3c Industrial Research Chair

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1 Pavement design fr lw vlume rads Guy Dré, ing., Ph.D. NSERC i3c Industrial Research Chair

2 Canadian Highways The Canadian rad netwrk: 1.04 millin km Wrld's seventh biggest netwrk. Paved rads: 415,600km Unpaved rads: 626,700km At least can be cnsidered Lw Vlume In Alberta, ~82% f the rad netwrk ( / ) is classified lcal rads

3 What is a «Lw Vlume Rad»

4 Lw vlume rads BC/AB: AADT < 200 Ont/Sask: AADT < 500 US: AADT < 400

5 LVR can be classified in 3 categries Rural System Rads Recreatinal Rads access t farms, residences, businesses r ther prperties access t and within islated cmmunities Traffic: light and medium vehicles and ccasinal heavy trucks. Primary Rads, which cnnect t the external rad netwrk, perimeter rads arund the recreatin area Recreatin area internal rads Traffic: cars, trailers, camper-truck units and maintenance vehicles. Resurce Develpment Rads Resurce related rads such as frest and mining rads. Traffic: predminantly large, heavily laded trucks.

6 Characteristics f LVR Lw vlume f traffic but vehicles can be very heavy Majr effect f climatic factrs Failure mdes and tlerance levels differ cnsiderably frm higher vlume rads Imprtant cnstraints related t cnstructin and maintenance f LVR (expertise, distance, available budgets, etc)

7 Pavement design appraches Experience-based design Empirical apprach Mechanistic-empirical apprach

8 Pavement design fr LVR Art r science? Mst methds are experience-based r empirical Mst empirical methds are extraplated frm general pavement design empirical mdels Sme mechanistic cnsideratins in a few mdels

9 Experience based design methds One r few predefined pavement structures Based n lcal experience General guidelines n layer thickness as a functin f site cnditins Example frm «Lw vlume rad engineering» (Keller and Sherar, 2003) High risk f ver/under design

10 Empirical design methds Methds based n empirical relatinships between site cnditins, traffic, pavement structure and level f service Relatinships develped using bservatins at experimental sites Generally develped fr high vlume rads and extraplated/adapted t LVR cnditins Extraplatin f empirical relatinships can lead t imprtant design errrs lg PSI 4,2 1,5 2,32lgM r 8,07 lg10 W18 ZR S0 9,36lg SN 1 0,20 0, SN 1 5,19

11 Example f empirical methd: AASHTO

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13 M-E methds Methds based n the calculatin f stresses and strains in the pavement structure Allwable stresses and strains btained frm empirical damage functins Pavement structure adjusted t meet allwable strain criteria Ratinale apprach t pavement design fr any type f rad Damage functins and criteria need t be adapted t lwvlume rad cnditins

14 Design bjectives adm Empirical damage functins Lg N M-E Pavement design Allwable strains MLEA mdel adm. adm. Layer thicknesses Site cnditins Sil and material prperties

15 Example f M-E methd: NCHRP 1-37a

16 Cmparisn f different LVR pavement design methds LVR design (AADT = 500; Clay subgrade) Hammit Girud and Niray TRRL AustRad AASHTO NCHRP 1-37A FCE AC/BST Base Subbase MTQ MTO Berthier (France) Ouest (France)

17 Pavement design fr lw vlume rads LVR represent an essential and a majr asset in Canada Rigrus design methds need t be used t maximize the perfrmance and the return n the investment n these rads Based n ur study, nne f the methds used in Canada allw fr ptimizatin f pavement design fr lw vlume rads

18 Pavement design fr lw vlume rads M-E pavement design methds are accessible and allw fr ptimizatin f pavement design fr LVR Perfrmance mdels and criteria need t be adapted t LVR and Canadian cnditins Emphasis n permanent defrmatin and frst heave

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26 Cnsideratins fr selectin f surface type Selectin f ptimal slutin requires a life-cycle cst analysis Cst infrmatin is highly variable depending n site cnsidered Reliable Infrmatin n perfrmance is difficult t find Other site specific cnstraints need t be cnsidered (availability f expertise, materials and equipment)

27 Cnclusin Lcal rads r «lw vlume rads» are extremely imprtant fr scial and ecnmic develpment in Canada Rigrus pavement design fr LVR is required t maximize the perfrmance and the benefit f these structures cnsidering limited resurces M-E design appear t be the best apprach

28 Cnclusin Research is needed T develp and imprve perfrmance mdels and design criteria adapted fr LVR and Canadian cnditins T adapt specificatin and characterizatin prcedures fr LVR materials T allw fr ptimisatin f LVR pavement structures and selectin f ptimal surfacing strategy

29 THANK YOU!