Pavement design

TRANSPORTATION ENGINEERING SEMESTER 2, 2018

KNE714 ASSIGNMENT 1 – FLEXIBLE PAVEMENT DESIGN

Due Date: 31st August 2018

Introduction A new bypass road is proposed around the town of Campusville. The bypass will replace an existing road that connects around the western edge of the town. The existing road has poor alignment and is no longer considered appropriate to service the region. A road corridor was reserved several decades ago for the new bypass, and a decision to construct a new road along this corridor has just been announced by the local government. The government has commissioned you to assist with the design of the new highway. The reserved road corridor is 7.5 kilometres in length along level terrain. The existing road around Campusville has an AADT of 15,600 vehicles per day in 2018. Existing traffic growth has been relatively consistent, averaging 2.2% per annum over the last 10 years. Traffic forecasting has been conducted, and it is expected that the new road will attract a higher growth rate and stimulate further growth in the region as a direct result of its construction. The additional traffic growth has been estimated to be 0.5% per annum higher than existing traffic growth trends. This level of additional traffic growth is expected to continue for 10 years. After 10 years, the additional traffic growth has been forecast to reduce to 2.0% per annum.

Pavement Design You are required to prepare pavement designs for the new bypass road. Various pavement alternatives must be considered for the new road based on the materials available, such as initial construction, maintenance costs and user costs. The preliminary designs are to be carried out using the Austroads Guide to Pavement Technology, Part 2, Pavement Structural Design (2012). Copies of appropriate design charts are provided. Other data needed for the design process are provided below. If you feel more data is necessary then assume or source what you need. You must provide the rationale for your assumptions and reference your sources. Traffic counts for existing road (flow is the total for all vehicles in both directions). ADT 15,600 Average Daily Traffic Volume (vehicles per day), 2018 CV 950 Commercial Vehicles (trucks per day), 2018 %CV 6.1% Percentage Commercial Vehicles of the ADT

Design Data for New Road Design Life : 20 years. Lane Distribution : assume 70% of CVs in outside lane if 4 lanes are used. Bitumen : Class 320 or Class 170 No. Lanes : Design dependent.

Material Properties The following materials are available for your use. The CBR and MR values refer to standard/ modified compaction. Costs are for materials supplied and “placed” at the site. Fine Crushed Rock (FCR) : CBR 90, MR 400-500 MPa. : : $32/m3 Quality Gravel : CBR 60 (soaked), MR 300-350 MPa. : $27/m3

Natural Gravel : CBR 40 (soaked), MR 200-250 MPa. : $19/m3 Select Fill : CBR 10 (soaked), MR 100-150 MPa : $12/m3 Asphalt (AC) : 2,800 MPa : $140/tonne Asphalt (AC) : 1,600 MPa : $137/tonne Double spray seal : to DIER specification : $6/m2 Cement Treated Material : 5,000 MPa Category : $56/m3 Cement Treated Material : 2,000 MPa Category : $52/m3

Task 1: Subgrade Conditions Geotechnical investigations have been undertaken along the road corridor. The results are attached. You are required to analyse the subgrade data and determine the appropriate subgrade conditions for the pavement design. As part of this design, you will need to determine whether subgrade lots will be required and whether any of sections of the subgrade require lime stabilisation treatment.

Task 2: Traffic Analysis and ESA Tasks:

(a) Induced Demand. It is noted that the traffic growth is not consisted throughout the design life of the pavement. The construction of the new road will cause the traffic growth to increase. Describe the fundamental reasons for this increase in terms of ‘induced traffic demand’ and any other factors that may be relevant.

(b) Traffic Capacity. You are required to perform a capacity analysis of the future road based on the traffic data provided. Based on your calculations you will need to state the number of lanes required for your pavement design. Clearly state all assumptions.

(c) Design Traffic. You are required to determine the design traffic (measured in Equivalent Standard Axles, ESA) for the pavement design based on historic and forecast future traffic growth.

Task 3: Pavement Designs and Selection

(a) The alternative pavement design types that must be considered for the bypass road during the evaluation phase are listed below. You may consider other options.

(i) A full depth granular pavement (granular base(s) and sub-base(s)), surfaced with

a double chip seal (Figure 8.4). (ii) A full depth granular pavement (base(s) and sub-base(s)) surfaced with asphalt

(you select the appropriate thickness of asphalt). (iii) Two pavements with cement treated base, surfaced with asphalt (you select the

thickness of asphalt). The two designs must differ in either materials and/or construction.

(iv) A full depth asphalt pavement.

(b) Each road pavement design should be costed based on the quantity of materials used.

(c) Make a final decision as to what you think is the most appropriate design for the bypass road. (Note that you are not necessarily restricted to the options in Part (a) above). When deciding what option to adopt you should consider pavement maintenance and general suitability. It should be obvious that you will need to make a number of assumptions, and these assumptions should be clearly identified.

Marks will be allocated to presentation, calculations, designs, innovative work and of course conclusions and comments.

Keith Midson BE MTraffic MTransport EngExec FIEAust CPEng NER 2018

Subgrade Conditions

Chainage (m) Subgrade CBR 0 4

250 5 500 4 750 4

1000 6 1250 5 1500 4 1750 4 2000 4 2250 4 2500 5 2750 2 3000 4 3250 5 3500 5 3750 6 4000 4 4250 5 4500 7 4750 8 5000 7 5250 6 5500 7 5750 7 6000 9 6250 7 6500 5 6750 6 7000 7 7250 8 7500 8