Highway & Railway Engineering

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Submission instructions
• All submissions to Module MOODLE Turnitin

Word Count: 6000 words +/-10% (excluding References, charts, tables and Appendices)
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Form of assessment:
Individual work
Number of assignment copies required:
1
Assignment to be presented in the following format:
Stapled once in the top left-hand corner OR
Plastic A4 folder (with see-through cover/slide binder)

Soft copy: All documents to be submitted online.
The assessment for this module consists of one piece of coursework weighted at 100% of the
overall unit and is to be submitted online on or before 4pm 12/05/ 2022.
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Project Brief
You are an engineer working for an engineering consultancy who has been
commissioned by a transport authority to provide technical assistance related to
the following highway and railway problems:
1. Highway maintenance, assessment and methods (20%)
1a). A site investigation was conducted on an existing highway pavement located in a
subtropical temperature environment. Sections of the highway have experienced
premature distresses such as that shown in Figure Q1.1. Overloading is a known
problem in the area. Results of gradation tests conducted on samples taken within
selected sections of the road revealed the particle size distribution shown Table Q1.1
and average air voids of 2.5%. Falling Weight Deflectometer (FWD) deflection data
indicated that the base can be considered as marginal. Based on the given information,
write a short report indicating what you think are the likely causes of the premature
failure. Clearly describe your approach assuming the pavements were designed using
UK pavement mix design standards. Clearly state all your assumptions. (15%)
1b). A section of the pavement was overlaid with 50 mm of asphalt concrete (AC) binder
course and 40 mm of AC wearing course. The pavement developed rutting (average rut
depth of 20 mm) during the first summer after construction. Which AC course has likely
contributed to the development of rutting? What is the most suitable way to determine
the layer causing the problem? (5%)
Figure Q1.1. Pavement section with premature distresses.
Table Q1.1 Gradation results for asphalt layer along highway route

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2. Highway Pavement Analysis and Design (30%)
A highway pavement is to be designed for the 2-lane access road servicing a large distribution
warehouse. The pavement is to consist of hydraulically bound material (HBM) base layer (C3/4)
surfaced with high quality asphalt layers. The exit lane (considered the design lane) pavement
is to be trafficked by heavily loaded trucks only. The following trafficking conditions apply:
• The exit lane pavement will be trafficked by 150 OGV2s trucks per day
• Each loaded truck has four axles of load 110kN and one (steering) axle of load 65kN as
illustrated in Figure Q2.1
• Assume a load equivalency factor of 4
• Sharp turns, braking and accidental loading are expected to contribute to about 50%
increase in the applied axle loads
• Number of operating days per year = 365
• Design life is estimated at 25 years
• The subgrade quality based on the falling Weight Deflection (FWD) deflection / backcalculated modulus inferred CBR of ranged from about 5-7% (40-98 MPa stiffness)
which indicates low quality, clayey soil with lot of plastic fines (Table Q2.1). Assume 15
percentile subgrade stiffness for design
• Tire pressure = 566 kPa
• Assume Figure Q2.2 represents the cross-section of the pavement to be designed
a) Determine the thicknesses of the HBM sub-base and the asphalt layers using CD 225. (5%)
b) Check the designs provided in a) using the WESLEA pavement analysis software focusing
on the critical pavement responses in the asphalt layer, the HBM subbase and the clayey
subgrade. Assume tensile strength of the HBM to be a minimum of 250 kPa. The stress
ratio is to be limited to 50% and the tensile strain limited to 120 microtrains. Maximum
tensile strain in the asphalt should not exceed 150 microstrains. Maximum compressive
strain in the subgrade should be limited to between 200-400 microstrains (20%)
c) Discuss the impact of overloading in HBM and in asphalt layers indicating which material
type is more sensitive to overloading. (5%)
Table Q2.1. Modulus of subgrade soil alone the highway alignment
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Figure Q2.1 Configurations of heavy trucks expected to use the proposed pavement
Figure Q2.2. Pavement cross-section.
3. Track structure analysis & design (25%)
a. Describe, with illustrations, four types of trackbed structures in common use
indicating some of their advantages and disadvantages. (10%)
b. For the track structure shown in Figure Q3.1, it is desired to replace the concrete ties
with wooden ties. Determine the reduction in service life as a result of the change from
wooden ties to concrete ties. Clearly state all assumptions made. You can use any
layer elastic analysis software of your choice, but it is recommended to us Kentrack
software as discussed in class. (15%)
Figure Q3.1. Structure for a ballasted trackbed.
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4. Environmental impacts (25%)
a. Discuss the different hardness tests for ballast and state their advantages and
disadvantages. (10%)
b. Discuss the factors that are critical to aggregates used for construction track ballast
high speed rail applications. (10%)
c. Discuss the different types of rail defects and their causes (5%)
Marking Scheme

Submission Requirements
1. Work is to be word-processed and this should be in a clear legible typeface.
2. All the work must be the student’s own. All written work to be put through
‘Turnitin’ and final report included with submission (maximum similarity index
30%).
3. Submissions must be properly structured; this may involve pre-planning your
work. The report must have an introduction, a contents page, rationale and
conclusion as well as the main subject matter.
4. All figures and tables must be appropriately titled within the body of the text.
5. All pages should be clearly numbered.
6. A bibliography and/or any references used must be provided. Referencing to be
Harvard Notation (if in doubt, check ‘Cite them Right’).
7. Sketches may be in pencil with inked notes or produced by computer.
8. Calculations must be logically laid out so that they can be easily checked.
9. All work submitted must have a front sheet that clearly shows the student ID,
module code and title, module instructor (s), academic term and academic year.
10.The work must be submitted on MOODLE “Turnitin” before the deadline.
11.Work which is submitted after the deadline but within 24 hours of the due date
and time will have 5% deduction in the marks, submission which is beyond 24
hours will receive zero marks, unless extenuating circumstances are approved.
SUBMISSION DATE: 16.00 12/05/ 2022