Civil engineering totur

Subject: Construct Transportation Design Services of the Proposed SR 76 (U.S. 79) in Carroll County in TN

The State of Tennessee Department of Transportation (TDOT) is in the process of completing the design of the proposed SR 76 (U.S. 79) in Carroll County. The proposed project begins, west of Cades-Atwood Road (Sta. 99+92 [+/-]) to East of S.R. 77 (Sta. 310+40 [+/-]). This project will tie Milan, TN to Mckenzie, TN by means of a four/five lane highway. There are two small towns, Atwood and Trezevant, between Milan and Mckenzie along S.R.76. This project along with the future ones will be a bypass around these towns. The attached contour map is a section of the project that bypasses Atwood.

The current project begins at Station 262+50 (+/-) and ends at the other side in a location, as shown in the contour map. The major Geotech information and traffic data for the project are also attached.

You are asked to propose the best possible route based on the existing ground profile and surrounding infrastructures and landscapes along with social and economic impacts. You are also asked to provide design services for about roadways consisting of some specific design features (earthwork, horizontal and vertical alignments, and structural design, as outlined later on of this announcement). The pavement must maintain good performance and effective level of service for 20 years. TDOT hereby is requesting that ASU-Jonesboro Transportation Group provide the following design services:

· Two alternative routes within the ROW limits and list potential problems that the routes may encounter, and choose the best route. The routes will be along the East-West direction.

Notes: Assume that you have the ROW as you need for the project and you want to maintain a level of service (LOS) A. But, the width of the ROWs will be considered based on the widths of traffic lanes (two lanes each way), shoulders (both sides), median, horizontal distance for slopped (side slope) part, about 2 ft clearance on each side for ease of excavation/fill and the widths of drainage ditches at both sides of the roadway.

· Horizontal alignment and cross-sections (profiles) at 100 ft interval the selected route. Please provide the alignment and profiles on separate 24”x36” or larger size sheets.

Notes: The profile width is the width of the roadway that will require earthwork. Consider the widths of traffic lanes (two lanes each way), shoulders (both sides), median, the horizontal distance for slopped (side slope) part, and about 2 ft clearance on each side for ease of excavation/fill. There will be one horizontal alignment. Show your vertical profiles on the sides (above and below the center of the profile). Your profile should show the natural elevation as well as the finished grade. The finish grade of the starting point (From Left in the contour map with a bearing of S48o13’18” E) of the project is the same as the natural grade of the supplied contour map. Assume that your starting station is 262+50 and the ground elevation is 462 ft. Your starting proposed finished grade at station 262+50 is 476.75 ft with an initial grade of +1.5%.

Locations and elements (stations, I, PI, R, L, LC, T1, T2, Superelevation, the degree of curve, 1, 2, c, l1, l2, lc, etc.) of all horizontal curves along the route. Show them on separate 24”x36” or larger size sheet(s).

· Locations and elements of all vertical curves (station, g1, g2, tangents, length, etc.) along the route. The cross-sections should indicate all relevant lane, shoulder, and side slope information. Show them on separate 24”x36” or larger size sheets.

· Mass Haul Diagram and the overhaul cost the roadway. The free haul distance is 500 feet. Assume an overhaul price of $15/yd3.station. Show the mass-haul diagram on separate 24”x36” or larger size sheets.

Notes: From horizontal and vertical profiles, you have the ordinates at each station. You calculate the end areas and then estimate the earthwork volume.

· Structural design (traffic lanes and shoulder) of flexible pavement using the AASHTO method. Show the typical cross-section on separate 24”x36” or larger size sheets.

Notes: Estimate traffic load based on traffic data (AADT, lane distribution, directional distribution, growth rate, etc.) given in the report.

· Estimate layer coefficients (a1, a2, a3) and drainage coefficients (m1, m2, and m3) based on material properties and drainage conditions. The value of m1 is 1 as it is for the surface layer. The values of m2 and m3 depend on the drainage condition.

· The inputs (Reliability, ESAL, Mr and, PSI, you can find out SN. For three different Mr values, you would get three SN values (one for the surface, one for surface+base, and one for surface+base+subbase).

· Use the following formula to find D1, D2, D3

SN = a1D1m1+a2D2m2+a3D3m3

Where, SN is estimated from the nomograph.

· Assume initial serviceability index, Pi= 5.0 and terminal serviceability index Pt=2.5

· For the Asphalt layer: Assume an elastic (resilient) modulus EAC= 450,000 psi

· For the Base: Use crushed gravels with Mr = 120,000 psi

· For the Subbase layer: Use AASHTO Soil type A-2 with Mr =40,000 psi

· For the Subgrade layer: Use the Geotechnical Report (soil type, etc.) to find Mr

· Compare with AASHTO recommended minimum layer thicknesses to choose the final thicknesses of pavement layers. In case your design thicknesses are lower than ASSHTO recommended minimum thicknesses, consider the minimum required thicknesses.

Special Note: For the drawings, you are not required to use any particular tool. You can use Word, Excel or free hand (pencil and paper) to complete your drawings. But, you are free to use any other tool such as AutoCAD that you are comfortable.

Conditions and Restrictions

Your design should accommodate the following conditions:

- At least one horizontal and one vertical curves

Provided Documents/Information

To assist you with the design, TDOT is providing the following:

- A sample of typical highway drawings

- Existing contour in electronic format

- Summary of the geotechnical report of the project

- Gradations of granular base materials and subgrade soils

Deliverables and Tentative Timeline

You should also submit the followings throughout the curse of this study:

1. A proposal consisting of significance, objectives, methodologies, task list, and timeline of your study.

2. Progress reports (oral and written) in the middle of this study. The progress reports should consist the overall progress the team has made, and plans for future.

3. An oral presentation earlier than the submission deadline the final written report.

4. A written report consisting of your abstract, methodologies, all the assumptions, steps, and calculations used to arrive at the design.

If you need additional information, please contact the instructor of the course.

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