Development of Design Guidelines for Rural Low Volume Roads in Malaysia

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25 ARRB Conference – Shaping the future: Linking policy, research and outcomes, Perth, Australia 2012

DEVELOPMENT OF DESIGN GUIDELINES FOR RURAL LOW VOLUME ROADS IN MALAYSIA Sufiyan Zakaria, Public Works Department, Malaysia Abdul Mutalif Abdul Hameed, Hameed, Public Works Department, Malaysia ABSTRACT The current annual road maintenance budget in Malaysia of about RM 580 million a year accounts for sizeable proportion of public expenditures. If road user costs or vehicle operating costs (VOC) are taken into considerations, the total expenditure by the road transport sector is even greater. As in most countries, the funding available for road maintenance is unable to meet increasing demands. As a result, it is imperative that road authorities make the more efficient use of the available funding. This paper presents details of a new design guideline for the structural design of low-volume roads, particularly in rural areas where there are local materials available for use in maintenance operations. The effective use of this guideline will also provide job opportunities to the local people who can be trained in maintenance operations.

INTRODUCTION It is widely recognized that a good road infrastructure is a pre-requisite to the continuing development of a nation. The economic contribution by the road network in Malaysia is enormous as it carries about 96% of all transported goods and passengers. The conservation of the condition of the road asset is therefore very crucial to ensure the network continues to be effective and maintains the required quality standards throughout its lifetime. Currently, there are more than 80,300 km of roads in Malaysia. The roads are divided into three broad categories: toll expressways, Federal roads and State roads. Federal roads are all roads declared under the Federal Roads Ordinance (1959). This category includes National Expressways Expressway s and highways administered by the Malaysian Highway Authority (MHA). There are about 17,500 km of Federal roads and about 61,000 km for State roads in Malaysia (Table 1). Table 1: Road categories and length Road category

Length (km)

Toll Expressways

1,700

Federal

17,500

State

61,100

As well as the need need to construct construct new roads to meet increasing increasing demands, demands, road authorities authorities are are aware of the need to maintain the existing road network in a serviceable condition. conditi on. The current annual road maintenance budget in Malaysia of about RM 580 million a year accounts for sizeable proportion of public expenditures. If road user costs or vehicle operating costs (VOC) are taken into considerations, the total expenditure by the road transport sector is even greater. As in most countries, countries, the funding funding available available for road maintenan maintenance ce is unable to meet increasing increasing demands. As a result, it is imperative that road authorities make the more efficient use of the available funding.

© ARRB Group Ltd and Authors 2012

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This paper presents details of a new design guideline for the structural design of low-volume roads, particularly in rural areas where there are local materials available for use in maintenance operations. The effective use of this guideline will also provide job opportunities to the local people who can be trained in maintenance operations.

DESIGN GUIDE FOR LOW-VOLUME ROADS Purpose The purpose of the Design Guide for Low-Volume Roads is to provide the Malaysian Highway Department (JKR) and consultants engaged in pavement engineering projects in Malaysia with a uniform process for the design of pavements for low-volume roads. The development of the Guide was based on various existing references and guidelines, including: 

Manual on Pavement Design (JKR Malaysia 1985)



Manual on Pavement Design of Flexible Pavement Structures (bin Harun, M.H. 2011)





Overseas Road Note 31 (Transport Research Laboratory and Overseas Development Administration 1993) Standard Specification for Road Works, Section 4: Flexible Pavements (JKR Malaysia 2008).

It builds on past JKR practice and experience and on design methodologies that have been successfully used in other countries. The design approach combines improved data and mechanistic methods of analysis into a single tool that is presented in the form of a catalogue of pre-designed pavement structures. The Guide is targeted at low-volume roads throughout Malaysia, including Sabah and Sarawak. This Guide contains procedures for the design of the following pavement structures: 



new flexible pavements for low-volume roads containing one or more bound layers new flexible pavements for low-volume roads consisting of unbound or stabilised granular materials capped with a thin asphalt surfacing.

For the purpose of this Guide, a flexible pavement consists of a bituminous paving material or a thin bituminous surface treatment placed over a granular road base and supported by a granular sub-base. Semi-rigid pavements include cement-bound or similarly stabilised basecourses consisting either of plant-mixed aggregate stabilised with cement, fly ash or lime or an in situ recycled and stabilised layer placed using cold in-place recycled (CIPR) techniques and incorporating additives such as bitumen emulsion, foamed bitumen or cement. The Guide does not address the structural design of rigid pavements.

Issues related to low-volume roads Low-volume roads are roads having a low average daily traffic (ADT) or a low number of cumulative Equivalent Standard Axle Loads (ESAL) over the design life. Low-volume roads can be equated with low-cost and even low-standard roads. Most of the documentation associated with low-volume roads cites about 250 vehicles per day (veh/day) as the upper limit for traffic. However, even this upper limit can be applicable to a lightly- or heavily-trafficked roads, depending on the type of vehicles using the pavement. Careful consideration needs to be given to the traffic growth rate because the assignment of accurate traffic growths and equivalence factors is crucial if economic designs are to be achieved. The use of unrealistically high growth rates or equivalence factors will demand the use of traditional pavement design approaches and construction methods required for more heavily-traffic roads. Whilst this reduces the level of risk for the engineer, it results in the adoption of conservative pavement designs which may not be required for low-volume roads.


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Another issue that needs to be considered is the need to relax the specifications for low-volume roads. For example, a common feature of the specifications for natural gravel base materials is the requirement that strict compliance criteria be met in terms of particle size distribution, Plasticity Index (PI below 6), and strength (soaked CBR greater than 80 at 98% Modified AASHTO compaction). In most cases, one of the biggest challenges faced by the engineer is where to source local materials which meet these specifications. Many natural gravels are often excluded because they fail to meet at least one of these criteria. Where materials meeting the specification are not available locally, the alternatives are to: 

import suitable materials, which can often involve haulage over long distances



improve the available materials by adding stabilising agents such as lime and cement.

STRUCTURAL PAVEMENT DESIGN The key information needed for the structural design of flexible pavements is: 

type and volume of commercial vehicles (CVs) for which the pavement structure is designed



design life of the pavement



subgrade type and strength



types and properties of available paving materials



environment to which the pavement structure will be exposed.

Determination of design traffic Traffic data is a key input parameter for the structural design of pavements. This information is needed to determine the loads that must be supported over the design life of the pavement. Two elements of traffic loading of particular importance are: 



standard axle or wheel load traffic spectrum and traffic volume – expressed as the expected number of standard axle loads that will be applied during the life of the pavement.

The ESAL in Malaysia is 80 kN, which corresponds to the standard axle load used in the AASHTO pavement design procedures. Traffic volume is calculated from a known or estimated volume of CVs and axle load spectrum. The traffic data considered in this Guide includes: 

number of CVs during the first year of the design period



vehicle class and axle load distribution



directional and lane distribution factors



traffic growth factors.

Two types of traffic characterisation data are currently available for structural pavement design in Malaysia: 



traffic volume and per cent CVs – this is available from the JKR national traffic data base, which is administered by the Highway Planning unit (HPU) axle load studies, which provide information regarding the axle load spectrum for selected roads and highways in Malaysia.

The axle configurations and corresponding load equivalence factors (LEF) used as a basis for the development of the Guide are shown in Table 2. For pavement design purposes, mixed


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traffic (axle loads and axle groups) is converted into the number of ESALs using load factors. The structural design of a pavement is then based on the total number of ESALs over the design period. Load factors can be determined from either theoretically-calculated or measured truck and axle loads. The information available from axle load studies carried out in Malaysia and from the current legal loads in Malaysia (Maximum Permissible Gross Vehicle and Axle Loads, RTA 1987, Weight Restriction Order 2003 ) was used to calculate commercial vehicle load factors for traffic classes monitored by the HPU (Table 2). Table 2: Axle configurations and Load Equivalence Factors (LEF) based on traffic categories Vehicle Class

Load Equivalence Factor (LEF)

C

0

Small trucks and vans (2 axles)

CV1

0.1

Large trucks (2 to 4 axles)

CV2

4.0

Articulated trucks (3 or more axles)

CV3

4.4

Buses (2 or 3 axles)

CV4

1.8

Motorcycles

MC

0

% CV

3.5

HPU class designation Cars and taxis

Commercial traffic (mixed)

The procedure for calculating the design traffic (number of 80 kN ESALs over the design period), is as follows: 1. From traffic counts for the project under consideration (information provided by HPU for the past 5 or more years), determine: a. initial average daily traffic in one direction (ADT) b. percentage of CVs with an unladen weight of more than 1.5 tonnes (P CV) c. average annual traffic growth factor (r) for CV. 2. Determine the following geometric design information: a. number of lanes b. terrain conditions (flat, rolling, mountainous). 3. Select design period. 4. Calculate the design traffic (number of ESALs) for the design lane and base year Y 1 (first year of design period) using the following formula: ESALY1 = ADT x 365 x PCV x LEF x L x T

(1)

where ESALY1

=

number of ESALs for the base year (design lane)

ADT

=

Average Daily Traffic

PCV

=

percentage of CVs (unladen weight > 1.5 tonnes)

LEF

=

Load Equivalence Factor

L

=

Lane Distribution Factor (refer to Table 3)


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T

=

Terrain Factor (refer to Table 3).

The value of LEF used in eqn (1) is 3.5 (weighted average distribution of commercial traffic and axle load). Note that the traffic in the primary design lane (one direction) decreases with an increasing number of lanes. In addition, as the terrain changes from flat to mountainous, the percentage of road sections with steep slopes and curves increases, thus increasing the stresses and strains induced in the pavement structure due to breaking, acceleration and cornering movements. Table 3: Lane distribution and terrain factors Number of lanes (in one direction)

Lane distribution factor, L

Type of terrain

Terrain factor, T

one

1.0

flat

1.0

two

0.9

rolling

1.1

three or more

0.7

mountainous/steep

1.3

5. Calculate the design traffic (number of ESALs) for the design period (design life in years) using the following formula: n

Design Traffic (ESAL DES) = ESALY1 x [(1 + r) – 1] / r

(2)

where ESALDES

=

design traffic for the design lane in one direction (determines the traffic category used as basis for selecting a pavement structure from the catalogue)

ESALY1

=

number of ESALs for the base year (Eqn (1))

r

=

annual traffic growth factor over the design period

n

=

design period (years).

Properties of subgrade Subgrade strength is one of the most important factors in determining pavement thickness, the composition of the layers and overall pavement performance. The magnitude and consistency of support that is provided by the subgrade is dependent on soil type, density and moisture conditions during construction and changes that may occur over the service life of a pavement. For pavement design purposes, several parameters are used to categorise subgrade support. Traditionally, the California Bearing Ratio (CBR) is widely used for this purpose and this has been retained in the Guide. The CBR values used for selecting alternative pavement structures from the catalogue (Figure 4) are 5-10%, 10.1-20%, 20.1-30% and >30%.

Properties of pavement materials The pavement design procedures presented in the Guide permit the use of a range of pavement materials, provided that they meet JKR Standard Specifications for Road Works. The choice of materials is based regional experience, the availability of materials and costs.


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Pavement materials are classified into several categories depending on their intended function within the pavement structure: 

bituminous wearing course (AC14)



unbound granular road base



cemented or otherwise stabilised road base



unbound granular sub-base.

Bituminous wearing course Specifications for bituminous mixtures are contained in the JKR Standard Specifications for Road Works (JKR Malaysia 2008).

Crushed aggregate and wetmix road base Unbound granular materials consist of crushed rock or gravel with an aggregate grading that provides a mechanically stable course that is capable of distributing effectively traffic loads transmitted by the overlaying bituminous courses. The performance of well-graded granular materials is largely governed by their shear strength, stiffness and the resistance to material break-down that may occur during construction or as a consequence of heavy traffic. The presence of excessive fine material and moisture has a detrimental influence on stiffness and stress distribution capacity. Adequate shear strength and drainage is usually obtained when the percentage of fine material ( ≤ 0.075 mm) does not exceed 10%. Temperature and loading time have no significant effect on the modulus, strength and durability of granular base materials. The JKR Standard Specifications for Road Works caters for two types of granular base material: 

crushed aggregate road base



wetmix road base.

Both materials are similar in composition, but construction practices differ. The minimum CBR requirement for crushed aggregate road base and wetmix road base is 80%.

Stabilised road base Stabilisation of a road paving material is used to correct a known deficiency or to improve its overall performance and thus enhance its ability to perform its function in the pavement. Base materials as well as the existing subgrade can be stabilised, either in situ or mixed with stabilisers in a plant and laid by a paver or other approved construction equipment to become the main structural layer. Plant-mixed stabilised material tends to be more uniform in composition and strength, and is preferred. If in situ stabilisation is used, then a cold recycler with an appropriate mixing chamber should be used. Both stabilised base materials and a stabilised subgrade must have a minimum CBR of 80% and an Unconfined Compressive Strength (UCS) of at least 0.8 MPa. The JKR Standard Specifications for Road Works addresses the following types of stabilised road base: 



aggregates stabilised primarily with cement and other binders aggregates stabilised primarily with bituminous emulsion or a combination of emulsion and cementitious material.

Materials stabilised with cement exhibit higher stiffness and strength, but are more prone to cracking. Materials stabilised primarily with bituminous emulsion usually have a lower structural stiffness but are more resistant to strain. Both stabilising agents can be combined to yield a paving mixture with desired performance properties.


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CATALOGUE OF PAVEMENT STRUCTURE FOR LOW-VOLUME ROADS The design catalogues for low-volume roads up to 0.5 million ESALs (ESALs), 0.5 to 1.0 million ESALs and alternative pavement structures for traffic up to 1.0 million ESALs are presented in Appendix A. A worked example is presented in Appendix B. Consideration can be given to adjusting pavement structures for low-volume roads based on local materials and practices if satisfactory performance records are available.

CONCLUSION This paper has presented details of a new design guideline for the structural design of lowvolume roads, particularly in rural areas where there are local materials available for use in maintenance operations. The effective use of this guideline will also provide job opportunities to the local people who can be trained in maintenance operations. The provision of road networks to improve accessibility for remote communities will be the main agenda for the Government of Malaysia in the future.

REFERENCES bin Harun, M.H. (2011), The new JKR manual on pavement design , final report, JKR 20601-LK0156-KP-05. Jabatan Kerja Raya (JKR) Malaysia (1985), Manual on Design of Flexible Pavement Structures , JKR 20601-LK-0156-KP-05, Arahan Teknik Jalan 5/85. Jabatan Kerja Raya (JKR) Malaysia (2008), Standard specification for road works, section 4: flexible pavement (JKR/SPJ/2008-S4 JKR 20403 0003 07). Roads & Traffic Authority (1987), Maximum Permissible Gross Vehicle and Axle Loads, Weight Restriction Order 2003. Transport Research Laboratory and Overseas Development Administration (1993), A guide to the structural design of bitumen-surfaced roads in tropical and sub-tropical countries , Overseas th Road Note 31, 4 ed, Overseas Centre, TRL, Crowthorne, Berkshire, UK.


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APPENDIX A

CATALOGUE OF PAVEMENT STRUCTURES FOR LOW-VOLUME ROADS [RETURN TO TEXT]

Table A1: Pavement structures for low-volume roads for traffic up to 0.5 million ESALs

CBR

CBR 2

CBR 3

CBR 4

CBR 5

CBR 6

CBR 7

0.05

0.1

ESAL (MILLION) 0.2 0.3

0.4

0.5

250

250

250

250

250

250

490

510

540

550

560

570

250

250

250

250

250

250

390

410

430

440

450

460

250

250

250

250

250

250

320

340

360

370

380

390

250

250

250

250

250

250

280

300

310

320

330

340

250

250

250

250

250

250 240

260

270

280

280

290

250

250 230

250

250

250

250

240

245

250

210 250

CBR 8 - 24

M n mum su ase t c ness o mm to e use Subbase material to have a CBR value >30%.

app ca e .

Legend: (Pavement layers thicknesses are in mm) Surface treatment Road base course (crushed granular material with maximum 8% fines) Sub-base course (crushed or natural granular material with maximum 10% fines)


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Table A2: Pavement structures for low-volume roads for traffic from 0.5 to 1 million ESALs CBR

0.50

ESAL (MILLION) 0.75

1.0

250

50 250

540

560

250

250

250

410

430

450

250

CBR 2 520

50

CBR 3

50

CBR 4

CBR 5

CBR 6

250

250

250

340

360

370

50

50

250

250

250

280

310

330

50

50

50

250

250

250

240

270

280

50

50

250

250

250

200

220

230

50

CBR 7

50

50 250 Minimum subbase thickness of 100mm to be used (if applicable).

CBR 8 - 24

Subbase material to have a CBR value >30%.

Legend: (Pavement layers thicknesses are in mm)

AC 14 Road base course (crushed granular material with maximum 8% fines) Sub-base course (crushed or natural granular material with maximum 10% fines)


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Table A3: Alternative pavement structures for traffic up to 1 million ESALs Pavement Types CBR

Conventional Flexible : Granular Base

Semi Rigid Pavement

Stabilised Base with surface treatment

50 100

CBR 5 to 10

200

200 CBR 10.1 to 20 150

300

50 100 150

250

50 200

CBR 20.1 to 30

CBR > 30

Legend:

50 100

100

100

50

50

100

100

100

100

200

200

(Pavement layers thicknesses are in mm) Surface treatment AC14 Road base course (crushed granular material with maximum 8% fines) Sub-base course (c rushed or natural granular material with maximum 10% fines) Stabilised s ubgrade (minimum 80% CBR & UCS ≥0.8 MPa) Stabilised base (minimum 80% CBR & UCS ≥0.8 MPa)


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APPENDIX B WORKED EXAMPLE

[RETURN TO TEXT]

DESIGN CALCULATION FOR LOW-VOLUME ROAD Desi gn a pavement for a 2-lane rural road i n a hilly setting with an average daily traffic of 100 vehicles. 20% of which are c ommercial vehicles with an un-laden weight > 1.5 tons. Assume a design period of 10 years with subgrade CBR of 5%.

Step 1 :Develop design input

ADT

=

100 vehicles

Pcv

=

20

%

Lane Distribution factor, L

=

1

(Table 1b)

Terrain Factor,T

=

1.3

(Table 1c)

Design life

=

10

years

=

2

%

Annual traffic growth, r Load Equivalence Factor (LEF)

=

3.5

(Table 1)

California Bearing Ratio, CBR

=

5

%

Step 2 :Determine design traffic (traffic category) ESALy1 (Base year)

ESALdes

=

ADT x 365 x Pcv x LEF x L x T

=

33,215

=

ESALY1 x [(1 + r) – 1] / r

=

363,704

=

0.36 million

=

5%

n

Step 3 : Determination of subgrade Result from subgrade testing, CBR

Step 4 : Select one of the pavement structures Option 1 : Selec t one of the pavement structures from Fig ure 2 Surface treatment (250mm)

Road base course (crushed granular material with maximum 8% fines)

(330mm)

Sub-base course (crushed or natural granular material with maximum 10% fines)

Option 2 : Select from Figure 4 (CBR = 5%, ESAL= 0.4 million) a. Stabilised subgrade w ith surface treatment Surface treatment (300mm)

Stabilised subgrade (minimum 80% CBR and UCS 0.8 MPa)

≥

b. Semi rigid pavement (50mm)


AC 14

(100mm)

Stabilised base (minimum 80% CBR and UCS ≥ 0.8 MPa)

(200mm)

Sub-base course (crushed or natural granular material with maximum 10% fines)

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25 ARRB Conference – Shaping the future: Linking policy, research and outcomes, Perth, Australia 2012 Copyright Licence Agreement

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Development of Design Guidelines for Rural Low Volume Roads in Malaysia

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