Optimum pavement design for Colombo SouthContainer Terminal Project

Yang Shu, BSc, AE, CCCC;1 Amila Chaminda WickramaArachchi, BSc;2 James Goh King Seng, MEng, PE, MHKIE3;

Chen Laijin, Bsc, SE, CCCC4

1Design Engineer, Level 32, East Tower of World Trade Center, Echelon SquareColombo 01, Sri Lanka; E-mail: yangshu@zjqhr.com2Design Engineer, Level 32, East Tower of World Trade Center, Echelon SquareColombo 01, Sri Lanka; E-mail: amilacwic@yahoo.com3Technical Director, Level 32, East Tower of World Trade Center, EchelonSquare Colombo 01, Sri Lanka; E-mail: jamesksgoh@gmail.com4Design Manager, Level 32, East Tower of World Trade Center, Echelon SquareColombo 01, Sri Lanka; E-mail: chenlaijin@163.com

AbstractThe Government of Sri Lanka (GOSL) has embarked on a $375.1-million expansion

program at the Port of Colombo, Sri Lanka to cater to the increasing demand ofservices in the international shipping industry.

China Harbor Engineering Company has been accepted by Sri Lanka PortAuthority (SLPA) as the Design and Built Contractor. During the Conceptual StudyStage the specified pavement type for the container yard have no difference betweenthe container pedestal and the area in-between the pedestals. However, the cost ofthe initial design exceeded the contractor’s budget. To solve this problem, our designteam is looking for the optimal pavement structure, which minimizes the cost whilemeeting all the engineering constraints.

This paper describes the optimum design for the loaded container stack and RTGrunway foundation. Traffic demand on truck and passing lanes was evaluated basedon estimated throughput including the effects of container type, size, block size anddwell time. The design followed the 2007 Structural Design of Heavy duty pavementsfor ports and other industries (4th edition). Finite element modeling was used todetermine design chart specified in the guideline.

The final solution should further consider the construction cost, constructionperiod, maintenance, Performance and Durability as well as operation management.

Keywords: Optimum Design; Container Yard; Heavy Duty Pavement.

1. Introduction

In 2011, the government of Sri Lanka (GOSL) has embarked on a$375.1-million expansion program at the Port of Colombo, Sri

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Lanka to cater to the increasing demand of services in theinternational shipping industry. The main features of theproject, known as the “Colombo South Container TerminalProject,” were the design and construction of a 1200m longquay structure with a minimum alongside water depth of -18.0mLWOST and development of approximately 60 hectares ofcontainer yard (CY) as well as the Buildings and relevantUtilities. China Harbor Engineering Company has been acceptedby Sri Lanka Port Authority (SLPA) as the Design and BuiltContractor.The detailed geological subsurface profiles of the

Geotechnical Investigation Final Interpretative Report(Construction Stage) shows the main subsurface soil is mediumto coarse sand and other harder layers. Only the southwest issurcharged with stone which is laid by adjacent project. TheReclamation Foundation has been treated with the vibro-densification and the bearing capacity at the final surfacelevel after ground improvement has achieved 150 kPa after theimprovement.At the conceptual design stage it was considered uniform

pavement section all over the stockyard. But the operationallayout clearly defined the loaded corners and those were fixedduring the service life of the terminal. Hence there was anopportunity to consider two different types of pavementstructures for loaded/unloaded areas.However, the cost of the initial design exceeded the

contractor’s budget. To solve this problem, our design teamwas looking for the optimal pavement structure, whichminimizes the cost while meeting all the engineeringconstraints. The structure form is proposed as below:1. Sub-base (If required) of unbound crushed rock2. Base course of cement bound material with

priming/geotextile3. Concrete block pavement

2. Pavement of Container Yard2.1. Definition of requirementFor the general design requirement of heavy-duty pavement,

there are four primary conditions.1. Low cost of construction.2. Low maintenance costs.3. High reliability.

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4. Known design life.Although no material meets all of these requirements

perfectly, it is believed by the engineers that a concreteblock surfacing with a cement bound base is the optimumsolution available today.A successful design must take the following parameters into

account:1. Port layout and operation2. Future uses and development3. Type of trafficking (vehicle speeds; wheel loadings;

number of loadings)4. Static loading (point loads; impact loading)5. Surface pollution (hydraulic oil; de-icing salts)6. Strength of subgrade7. Anticipated settlement (short term; long term)8. ClimateThis list is by no means exhaustive.With so many design parameters it is virtually impossible to

put forward a comprehensive design method which would coverall plausible conditions; the graphical and tabularpresentation required would be formidable.In this paper The Structural Design of Heavy Duty Pavements

for Ports and other Industries by INTERPAVE (2007) (hereafter referto SDHDP) is referred to set up the design guide..

2.2. Pavement Design and Analysis MethodPavement design has been, indeed still is, empirical. The

variability of the materials making up the pavement structurehas, until recently, made it difficult to develop a suitableanalytical design philosophy. However, the wide use ofcomputers has brought a semi-analytical approach to pavementdesign in the past few years, and this has also made itpossible to extend the empirical design rules beyond theiroriginal bounds of development to include motorways and heavyduty pavements.The most successful of these analysis techniques has been the

multi-layer elastic model. Several programs of varying degreesof complexity have been developed, and this work uses asimplified analytical technique developed by Ullidtz andPeattie. This has been adopted because of its speed ofexecution, particularly when several hundred pavement

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structures are being analyzed, as is the case for each designchart.The pavement model is shown in Figure 1. The contact area

between the tyre and the pavement is assumed to be circularwith a contact stress equal to the tyre pressure. The analysisprogram gives the vertical stress and strain, and the radialstrain at each interface. Two design criteria have beenestablished and generally applied to pavements:1. Fatigue cracking of base material.2. Progressive vertical deformation of the subgrade.Thus the two design parameters in the structure are the

tensile radial strain at the bottom of the bound layer and thecompressive vertical strain at the top of the subgrade.Relationships have been developed between these two strainsand the design life, i.e. the number of load repetitions tofailure of the pavement.

Figure 1. The pavement model (ER2 is the critical strain in the base. EZ4is the critical compressive strain in the sub-base).

Thus with computer analysis it is possible to establish thesecritical strains for a whole range of pavement structures andplot the results as a design chart. In order to produce thedesign charts, pavements have been analyzed using the finiteelement method in which a model was developed to represent allcomponents of a pavement. Elastic properties and Poisson’sRatio values were chosen to describe the behaviour of eachpavement component. Fatigue is taken into account by defininglimiting stresses to which the pavement can be exposed for oneload pass and then by reducing those stresses to account forthe fatigue effect of multiple load repetitions.Interalia, trafficking tests of block pavements have

established that:1. In general block pavements tend to perform in a manner

which is qualitatively similar to conventional flexible

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pavements save for a few crucial differences in behaviourlisted below.2. An increase in block thickness within the range from 60 to

100 mm is beneficial to pavement performance.3. Under trafficking, block pavements tend to develop

interlock. This is manifest as increases in the load-spreadingability of the blocks and reductions in the rate ofaccumulation of deformation4. Once a block pavement constructed on a granular base

course becomes fully interlocked it attains a stableequilibrium condition which is unaffected by either the amountof traffic or by the magnitude of the wheel load (within therange from 24 to 70 kN)5. Once interlock has developed the blocks act as a

structural layer rather than merely as a wearing course.6. Block pavements incorporating a granular base can

typically exhibit elastic deflections between 1 and 2 mm whileat the same time. yielding only small rutting deformations.

3. Design Example

The optimum design work scope of the pavement design of thecontainer stockyard includes the container stack foundations,support, pavement and the like in the container stock of theterminal. All container yard roadways are excluded in thisdesign package, the container stockyard pavement, foundation,and support design are grouped as follows: 1. RTGC runway2. Trailer lane3. Loaded container stockyard4. Empty container stockyardThis paper will describe the design method used for loaded

container and the RTGC runway as examples.

3.1. Container Stockyard LayoutThe layout and dimensions of the container stacks and empty

container stacking areas are shown in Figure 2.

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Figure 2. Container Stockyard Layout

The container yard is divided into four main blockssurrounded by internal roads and the all container stacks willbe oriented horizontally and parallel to the quay. Each blockof stacking area will contain 10 stacks. The paving &surfacing container yard cross-section is shown in Figure 3 &Figure 4.

Figure 3. The paving & surfacing container yard cross-section

Figure 4. The paving & surfacing container yard cross-section

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3.2. Loaded Container Pavement Design

3.2.1. Loaded Container Stack Arrangement:

Each stack will be laid out for stacking loaded containerssix rows wide and six high under one high-cube over six high-cube tiers spanning six rows plus a tractor lane. Reefercontainers will be stacked five high. The stacking layout willalso allow a minimum of 400 mm between the ends of all boxes,and 400 mm between the sides of boxes to be handled by RTGCs.The arrangement of the loaded container stockyard is shown inFigure 5.

Figure 5. The paving & surfacing container yard cross-section detail

3.2.2. Container Yard Design Criteria

The container yard paving and container supports will bedesigned, as minimum requirements, to support loads fromcontainers to suit the stacking configuration.Container stack foundations shall be designed for container

stacking using recommended loads and stacking height reductioncoefficients from "The Structural Design of Heavy DutyPavements for Ports and Other Industries 4th Edition " and themaximum stacking height of the yard equipment. The UDL iscalculated on the basis of 20 ft long containers with a ratedload of 25 tonnes and 100mm clearance between containers. Thecorner load of one container is based on 40 ft long containerswith a rated load of 30 tonnes.

TABLE 1. CONTAINER LOAD

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Stackheight

Reductioncoefficie

nt

Equivalent UDLkN/m2

Cornerload forsingle

stacks kN1 1.0 16 752 0.9 28 1353 0.8 37 1804 0.7 44 2105 0.6 47 225

(Corner castings assumed to measure 178 mm x 162 mm)

3.2.3. Design Method:

According to clause 8.9 of the structural design of heavyduty pavement for port and other industries, corner castingsassumed to measure of 178mm x 162mm is adopted.In this design, only static loads from container corner

casting feet are applied on the pavement, no traffic loadingis considered in the design of loaded container stockyardpavement. The static loads from container up to six high is taken from

Table 2, considered laden maximum gross weight reduction of40% is used for the design.

TABLE 2. PAVEMENT LOAD FROM STACKING FULL CONTAINERSStack

height

Reductionin GrossWeight

ContactStress(N/mm

2)

Load on Pavement(kN) for each stackingarrangement

Singly Rows Stocks

1 0 2.59 76.2 152.4 304.82 10% 4.67 137.2 274.3 548.63 20% 6.23 182.9 365.8 731.54 30% 7.27 213.4 426.7 853.45 40% 7.78 228.6 457.2 914.46 40% 9.33 274.3 548.6 10977 40% 10.9 320.0 640.0 12808 40% 12.5 365.8 731.6 1463

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Figure 6. Container base with CBM concrete strips

As per Table 2 Load on Pavement is 1097kN corresponding to 6stack height from the design chart and the required basethickness of C8/10 material is proposed to be 605 mm. Typicalcross sections of initial proposal and the optimum design areshown in Figure 7 & Figure 8.

Figure 7. Typical Cross section for load container pavement of initialproposal

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Figure 8. Typical Cross section for load container pavement of optimumdesign

3.3. RTG RUNWAY DesignDesign of the RTGC runways is consistent with BS 8110 and

with reference to SDHDP.RTG runways is designed for 40 tonnes nominal capacity RTG.

The runways is designed for the loads applied by stationary,loaded RTGs (12,000 loadings per annum), and by unladen,travelling RTGCs (for 65,000 passes per annum).

3.3.1. Design consideration and input parameter

The design life is 60 years and the design conditions arespecified as Table 3.

TABLE 3. DESIGN CONDITION FOR RUNWAY PAVEMENT

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SerialNo. Design condition

1 Dynamic condition + loadedcondition

2 Dynamic condition +unladen condition

3 Static condition + loadedcondition

4 Static condition + unladencondition

The design input parameter that influent the runwayfoundation design are:1. Material type of runway beam Concrete-C40(20) High yield Steel reinforcement, fy=4602. Traffic loading No. of Passes per annum for laden condition is 12,000

loadings No. of Passes per annum for laden condition is 65,000

loadings3. Crane Details No. of tyres is 8 Configuration parameter of RTG is as Figure 8 and Figure

9. Nominal Capacity of RTG is 40 tons Maximum Tyre Load of the RTG crane is 23 tons The weight of unladen RTGC is 154 tons

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Figure 9. Configuration Parameter of RTG

3.3.2. The Design Procedure

The design procedure of due runway foundation and runway beam(take dynamic condition as example) can be summarized asfollows：1. Decide on the design life of the foundation which is 60

years 2. Estimate the axel passes over the life period, 3.744

Millions3. Estimate CBR of the subgrade which is 5%.4. Based on effective CBR of subgrade, the effective depth of

wheel load can be approximated from the following formula.Effective depth=3003√35000/(CBR10)

(1)5. The proximity effect can be calculated by Table 19 of

SDHDP and the proximity factor is supposed to be 1.28. 6. Choose a dynamic factor. The effects of dynamic loading

induced by cornering, accelerating, braking and surfaceunevenness are taken into account by the factor, fd is 1.2(Braking on uneven surface)7. Reaction calculations of RTG were carried out by static

equilibrium shown on Figure 9, ie. W1=80.32t, W2=113.68t.Therefore, the maximum tyre pressure is supposed to beTstatic=W2/4=28.4t8. Considering the most adverse loading case of braking on

uneven surface and apply the appropriate dynamic factor of±20% to the wheels at the extreme front and rear, applying theincrease in load to the front wheels and the decrease to the

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rear wheels. The inner wheel loads need to be similarlyadjusted but using a factor lower than ±20% determined byconsidering relative distances from the wheels’ center line.The load distribution are as below

TABLE 4. DYNAMIC TYRE PRESSUREWheelNo.

Dynamic tyrepressure

1 34.1ton2 31.9ton3 25.0ton4 22.7ton

9. For the maximum wheel load effect of loaded condition,SEWL, which means the Single Equivalent Wheel Load is428.52kN.10. With one pass of the RTGC 4 Nos of wheels passes which

has loads of different magnitude. This effect to be simulatedas a fraction of SEWL & finally taken into account as anincrement of repetitions. The simulative factor shall bedenoted as below

Simulative factor=(P/SEWL)3.75

(2)Where P is the respective wheel load effect.11. Repeat step 7 to 10 for all the design conditions to

figure out the critical design requirement. In term of designchart and Table 13 of HDP the required runway foundation canbe proposed as below.

TABLE 5. PROPOSED RUNWAY FOUNDATION

Pavement Proposedthickness

C-40Concrete

350mm

C-15Bedding

75mm

Stabilizedbase

150mm

Sub Base 150mm

12. RTG runway beams were analyzed as long RC beams supportedon springs assuming a subgrade reaction modulus, ks, of 22500kN/m2/m. The beams were subjected to loads associated with RTGcranes and applied as either static (operating) or movingloads. Figure 10 shows pressure distribution of RTG below theaxels.

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Figure 10. Pressure distribution Below the AxelsRTG runway beam are 1.5 meter wide and 0.35 meter deep with

control (doweled) joints spaced every 11.5 meters. A typicalcross-section is shown in Figure 11.

Figure 11. RTG runway detail4. ConclusionThe feasible solution may not be decided purely on the

initial construction cost. We should further consider theconstruction period, Maintenance work, Performance andDurability of each proposal. What’s more, the selection ofdesign proposal is also related to the operation management.

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The summarized proposal estimate which is intended to providecomparable cost and technical information for the alternativedesign is as Table 6

TABLE 6. PROPOSED RUNWAY FOUNDATIONComparis

onDescript

ion

Initial Proposal

Optimized Proposal

CostComparison

approximately 55,000,000USD approximately 39,000,000USD

Durability

More than 100 years More than 60 years

Performance

Flat and level, Flexibility ofthe pavement is less. There islittle uneven settlement.

Flat and level,Flexibility of thepavement is high. Thesignificant unevensettlement.

Construction andMaintenance

Huge construction quantities,there is not too muchmaintenance work duringoperation period but it’sdifficult to do once it’sdamaged.

Requires regularmaintenance afterputting into service,but it can be easilyaccomplished.

The cost of initial proposal is quite high and theflexibility of the foundation is not good enough. We canemploy the initial proposal with the support of sufficientfunding. But with respect to the cost of the project and thegeneral performance, the optimized proposal prevails.

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5. References

5.1. Journal Article[1] M.N.S. Hadi and Y. Arfiadi. Computers and Structures. 79, 1617 (2001)

[2] Zhao Jianchao. Port & Waterway Engineering. 11, 46 (2004)

5.2. Book [3] YANG H. HUANG, Editor, Pavement Analysis and Design, Published byPearson Education, New Jersey (2004)

[4] John Knapton, Editor, The Structural design of heavy duty pavements for ports and other industries, Published by Interpave, Leicester (2007)

5.3. Conference Proceedings [5] Carlos E. Ospina and Viswanath K. Kumar, Editors. Ports 2010: Building on the Past, Respecting the Future. Proceedings of the 12th Triannual International Conference on Ports, (2010) October 912-921; Florida, United States

[6] S.D. Barber and J. Knapton, Editors. Structural Design. Proceedings of the 1st International Conference on Concrete Block Pavement, (1980) September 141-149; Newcastle, British

[7] Joao Santos and Adelino Ferreira, Editors. Procedia: Social and Behavioral Sciences. Proceedings of the 5th International Congress onSustainability of Road Infrastructures, (2012) October 1184-1193; Rome, Italy

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