204 EMBANKMENT AND SUBGRADE
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- Construct embankment and subgrade using suitable material obtained from roadway, structure, borrow, and other excavation included in the Contract. Place, process, and compact material to the specified line and grade.
- Unless otherwise specified, use soils and soil aggregate mixtures that meet the common borrow requirements specified in Section 916.
- 204.02.01 Rock. Rock may be used in embankments, if individual pieces do not exceed 24 in. in any dimension. Larger size rocks may be wasted with the approval of the Engineer.
- 204.02.02 Frozen Material. Refer to 201.03.05. In addition, do not cover any material that freezes after being placed in the embankment until it has thawed.
- 204.02.03 Embankment Adjacent to Structures. The Engineer may require the use of specially selected material adjacent to structures to protect the structure from damage. Do not use rock. At locations of pile supported foundations, use embankment material that will allow piles to be easily driven.
- 204.03.01 Embankment Foundation
- (a) Foundation Material. The Engineer will inspect and approve the area prior to construction of the embankment. Remove topsoil, root mat, and unsuitable material to the depth directed.
- (b) Embankment Over Existing Pavement. Thoroughly break up, scarify, or remove the pavement as specified or as directed.
- (c) Test Rolling. When specified or directed, test the foundation by rolling with a 35 ton pneumatic tired roller, or as approved.
- 204.03.02 Placing and Spreading. Place the material in horizontal layers across the full width of the embankment. Maintain an adequate crown to provide drainage at all times. Maintain side slopes at the specified slope throughout the progress of the work.
- (a) Embankment on Unstable Ground. When embankment is to be constructed on ground that will not support the weight of the construction equipment, the first layer of the fill may be constructed by depositing material in a layer no thicker than that required to support the equipment. Place subsequent layers as specified in (b).
- (b) Earth Embankment. Except when specified, do not place layers exceeding 8 in. compacted depth.
- (c) Rock Embankment
- (1) Determine the thickness of layers by the size of the rock or a 24 in. maximum depth, whichever is less. Where the embankment is less than 6 ft below the subgrade at the profile grade line, place the material in layers not exceeding 8 in. compacted depth. Solidly fill and choke these layers with spalls, rock dust, or earth. Fill and compact each layer before placing the next layer.
- (2) Place the rock material to a uniform top surface, determined by connecting with straight lines the points on the typical cross section that are 9 in. below any median ditch invert and 9 in. below the bottom of the pavement structure and then sloping downward and outward under the shoulders at the rate of 3/4 in. per ft to the outer slope of the embankment.
- (3) Unless otherwise specified, construct the remaining upper portion of the embankment, using suitable earth that is free from stones retained on a 3 in. sieve.
- 204.03.03 Benching. When placing and compacting embankment on hillsides or against existing embankments, continuously bench the slopes where the slope is steeper than 4:1 when measured at right angles to the roadway. Perform the benching operation as the embankment is constructed in layers. Maintain a bench width of at least 5 ft. Begin each horizontal cut at the intersection of the original ground and the vertical sides of the previous cut. If the material cut from the benches meets embankment requirements, compact this material along with the new embankment material.
- 204.03.04 Compaction. Immediately after spreading each layer of fill, compact the material with approved equipment. Perform all rolling in a longitudinal direction along the embankment. Begin at the outer edges and progress towards the center. Vary the travel paths of traffic and equipment over the width of the embankment to aid in obtaining uniform compaction.
- Compact the material that is 1 ft below the top of subgrade to at least 92 percent of the maximum dry density according to T 180. Compact the top 1 ft to at least 97 percent of the maximum dry density. Determine in-place density according to MSMT 350 or MSMT352. When necessary, add water or dry the layer in order to compact to the required density. When finally compacted to the required density, the resultant moisture content of embankment material shall be within two percentage points of optimum.
- Provide a portland cement concrete compaction block having dimensions 18 in. x 18 in. x 9 in., weighing at least 200 lb, and with one 18 in. x 18 in. level and broomed working surface.
- 204.03.05 Stability of Embankments. Remove and replace with acceptable material any embankment or portion thereof that has been constructed with unsuitable material. Remove and replace unstable material and remove and replace portions of the embankment that become unstable or displaced as the result of the construction operations.
- 204.03.06 Protection of Structures and Utilities During Construction. Protect all structures and utilities from any damage in the handling, processing, or compacting of embankment or backfill material. Exercise caution near arches, retaining walls, culverts, and utility trenches to prevent undue strain or movement. In areas where rollers cannot be used, refer to Section 210.
- 204.03.07 Subgrade. After all cuts, embankment, and backfilling have been substantially completed, construct and shape the subgrade to the specified cross section. Test roll the subgrade as specified in 204.03.01(c).
- 204.03.08 Maintenance. Maintain the embankment and subgrade until final acceptance. Use acceptable material from excavation or borrow to replace embankment and subgrade material that may be lost or displaced as a result of natural causes such as storms and cloudbursts, or as a result of unavoidable movement or settlement of the ground or foundation upon which the embankment and subgrade is constructed. Maintain ditches and drains at all times. Keep all traffic on the embankment and subgrade to a minimum. Remove ruts that are 2 in. or more in depth by reshaping and recompacting.
204.04 MEASUREMENT AND PAYMENT
- Embankment, subgrade, and all necessary work will not be measured but the cost will be incidental to the Contract unit price per cubic yard for the pertinent Class of Excavation. The payment will be full compensation for the formation, sprinkling, compacting, test rolling, shaping, scarifying, breaking or removing of the existing pavement, sloping, trimming, finishing, maintaining embankments and subgrade, and for all material, labor, equipment, tools, and incidentals necessary to complete the work.
- Replacement of material lost as a result of natural causes will be measured and paid for at the Contract unit price per cubic yard for the pertinent Class of Excavation item or as directed by the Engineer.
- Compaction by means of mechanical tampers or vibratory compactors will not be measured but the cost will be incidental to the pertinent Class of Excavation item.