207.01 183 SECTION 207 – SUBGRADE CONSTRUCTION AND PREPARATION
207.01 Description ................................ ................................ ................... 183
207.02 Reserved ................................ ................................ ....................... 183
207.03 Preparing Subgrade ................................ ................................ ...... 183
207.04 Compacting Subgrade ................................ ................................ .. 184
207.05 Drainage and Protection ................................ ............................... 184
207.06 Checking Subgrade ................................ ................................ ...... 185
207.07 Disposal of Excess or Unsuitable Material ................................ .. 185
207.08 Method of Measurement ................................ .............................. 185
207.09 Basis of Payment ................................ ................................ .......... 186
DESCRIPTION
207.01 Description
This work consists of constructing and preparing part of or all the roadbed to a condition suitable for supporting the immediate construction of a base or pavement.
207.02 Reserved
CONSTRUCTION REQUIREMENTS
207.03 Preparing Subgrade
Perform Excavation and Undercutting as specified in 203. Where the roadbed is below grade, haul, spread, and compact, as specified in 205, suitable material in sufficient quantity to bring the r oadbed to grade. Where the roadbed has been seeded for erosion protection or has established vegetative growth, clip the roadbed to remove vegetation and other deleterious material before placing the base or sub base material. Correct depressions resulting from the removal of deleterious material by hauling, spreading, and compacting suitable material as specified in 205. 207.04 184 Where sub bases are to be constructed on the subgrade, extend the limits of subgrade preparation across the entire section that will receive the subbase course, including the shoulders. Where forms are required to construct base or pavement, prepare the subgrade 12 inches wider, on each side, than the neat width of the base or pavement.
207.04 Compacting Subgr ade
On subgrades that require reworking, remove all vegetation within the limits of subgrade preparation, and dispose of this material as directed by the Engineer before beginning reworking and re -compacting operations. The dens ity of the finished subgrade shall not be less than 100% of the maximum density. The optimum moisture, maximum density, and density of the soil in place will be determined in accordance with 205.04. If field tests show failure to meet the density requirement, loosen the subgrade by discing, harrowing, or other approved methods to a depth of not less than 6 inches, then reshape and re -compact the subgrade material as specified in 205.04. Moisten or aer ate the subgrade material as necessary during mixing and compacting to provide optimum moisture content as specified in 205.04. Rework, or remove and replace, all soft, yielding material that will not compact readily, and compact the replacement material as specified in 205.
207.05 Drainage and Protection
Grade the subgrade to provide for ready drainage of water from the subgrade. Maintain ditches and drains to provide proper drainage during the construction. Take all precautions necessary to protect the subgrade from damage. Limit hauling over the finished sub grade to that which is essential for construction purposes. Correct ruts or rough places that develop in a completed subgrade and re - compact as necessary. 207.06 185 207.06 Checking Subgrade Check the lines, c ross-sections, and grades of the subgrade as completed to ensure they are in reasonably close conformity with those shown on the Plans for the bottom of sub base, base, or pavement, or with those established by the direction of the Engineer. Construct the subgrade to the grading line show n on the Plans, with an allowable working tolerance of plus or minus 1 inch. Recheck the subgrade as specified in the respective sections governing construction of the particular type of base and pavement.
207.07 Disposal of Excess or Unsuitable Material
Dispose of excess or unsuitable material as specified in 203.07. COMPENSATION
207.08 Method of Measurement
The Department will measure items of construction as follows :
1.Subgrade Construction and Preparation will be measured by the station (100 feet) along the median centerline of the Project for divided sections, and along the centerline of the pavement for 2 -lane and other undivi ded sections, excluding bridges .
2.The volume of excess or additional material moved, or of unsui table material removed, will be measured in cubic yards by the cross - section method, or if that method is unfeasible, by some other method, with the volume computed for payment in accordance with 109.
a.If grading has been performed under a previous Contract, the Department will measure the number of cubic yards of unsuitable material below subgrade elevation, acceptably removed and disposed of, in both cut and fill sections under the item for Road and Dr ainage Excavation (Unclassified) in accordance with 203.09.A. 207.09 186 b. If grading is included in the Contract, the Department will measure the number of cubic yards of unsuitable material below subgrade elevation in cut sections, acceptably removed and disposed of, under the item for Undercutting in accordance with
203.09 E. In the subgrade of embankment sections, the
Department will not measure the removal and disposal of excess or unsuitable material for payment.
3.Water required for compaction by the M.G. (1,000 gallons) will be measured using calibrated tanks or distributors, or accurate water meters.
207.09 Basis of Payment
The Department will pay for accepted quantities at the contract prices as follows: Item Pay Unit Subgrade C onstruction and Preparation Station Payment for Subgrade Cons truction and Preparation per 100 -foot station is full compensation for shaping and compacting the roadbed, all ramps, service roads, approaches, roadside rest areas, and similar features , as shown on the Plans. If the material to be placed or removed does not exceed a depth of 3 inches, this payment also includes the moving or furnishing of all additional material required, or the disposal of excess material. If a depth of 3 inches is exceeded, the Department will pay for the total quantity of material re moved or placed at the appropriate contract unit price per cubic yard for Borrow Excavation (Unclassified) or Road and Drainage Excavation (Unclassified), as provided in 203. If the Contract includes the construction of the c ombined grading, drainage, and pavement structure, the Department will consider the construction and preparation of the subgrade as incidental to the construction and preparation of the road, and the material moved will be classified and included in the computation of pay items provided in 203. If the Contract provide s for the construction of a sub base, base, or pavement on a road that has been graded under a previous contract, and the i tem for Subgrade Construction and Prepa ration is included in the Contract, the Department will pay for this item at the contract unit price per 100 -foot station. Payment for material moved will be subject to the stipulations set forth above. 207.09 187 Unless otherwise shown on the Plans, the Department will consider clipping of a roadbed that has been seeded as incidental to other items of construction. The Department will pay for Water applied as directed by the Engineer at the contract unit price per M.G. (1,000 gallons), as provided in 203. 208.01 188 SECTION 208 – SHOULDERS AND DITCHES
208.01 Description ................................ ................................ ................... 188
208.02 Materials ................................ ................................ ...................... 188
208.03 Equipment ................................ ................................ .................... 188
208.04 General ................................ ................................ ......................... 189
208.05 Final Cleanup ................................ ................................ ............... 189
208.06 Method of Measurement ................................ .............................. 189
208.07 Basis of Payment ................................ ................................ .......... 189
DESCRIPTION
208.01 Description
This work consists of constructing shoulders and ditches adjacent to both sides of the base or pavement to obtain proper drainage. MATERIALS
208.02 Materials
The Contractor may obtain material for constructing shoulders as approved by the Engineer. Provide additional material, if required, from approved sources. EQUIPMENT
208.03 Equipment
The Contractor may perform compaction operations using any type roller that will produce the required results.
Source: Tennessee Standard Specifications for Road and Bridge Construction, 2021 Edition. Pages 192–196 of 1,072.