FORMATION OF EMBANKMENT



28.1 Scope

This Work shall consist of the formation of embankment in accordance with these Specifications and the Specifications for other Work items involved and in conformity with the lines, grades, Sections and dimensions shown on the drawings or as required by the Engineer.

28.2 Material Requirements

Material for embankment shall consist of suitable material excavated as per Project Specifications and approved by the Engineer. Borrow material, however, shall only be used when there is no suitable material available from cuts made from the roadway, in conformity with the lines, grades, Sections and dimensions shown on the Drawings or as required by the Engineer. Material having A-3 AASHTO Classification shall not be used.

Wet excavated material which will be suitable when dry and if approved by the Engineer shall first be allowed to dry and attain optimum moisture content before being placed in the embankment.

28.3 Construction Requirements

28.3.1 Formation of Embankment with Common Material

(i) Material for embankment, obtained and approved as provided above, shall be placed in horizontal layers of 6” thick uniform thickness after compaction and in conformity with the lines, grades, Sections and dimensions shown on the Drawings or as required by the Engineer. The layers of loose material other than rock shall be not more than 8 inches thick, unless otherwise allowed by the Engineer after a trial Section is prepared and approved.

(ii) The material placed in all embankment layers and the material scarified to the designated depth shall be compacted to the density specified in the following table:








Depth in inches below
Subgrade Level Percent of AASHTO T-180 (Method-D)
Maximum Dry Density
00 – 12 95%
12 – 30 93%
More than 30 90%

(iii) In place density determinations of the compacted layers shall be made in accordance with AASHTO T-191 or other approved methods. For all soils, with the exception of rock fill materials, containing more than 10% oversize particles (retained on 3/4 inch), the in-place density thus obtained shall be adjusted to account for such oversize particles as directed by the Engineer. Subsequent layers shall not be placed and compacted unless the previous layer has been properly compacted and accepted by the Engineer.
(iv) Material for embankment at points inaccessible to normal compaction equipment shall be placed in horizontal layers of loose material not more than 8 inches thick and compacted to the densities specified above by the use of mechanical tampers, or other appropriate equipment.
(v) The compaction of the embankment shall be carried out at the designated moisture content consistent with the available compacting equipment. In forming the embankment. The Contractor shall take steps to ensure that the Work can be drained free of rain water, and he shall make due allowance in the height and width of the Work for swelling or shrinkage.
(vi) Embankment material that does not contain sufficient moisture to obtain the required compaction shall be given additional moisture by means of approved sprinklers and mixing. Material containing more than the amount of moisture necessary to obtain the required compaction may not, without written approval of the Engineer, be incorporated in the embankment until it has been sufficiently dried out. The drying of wet material may be expedited by dispersing or other approved methods.
(vii) When materials of widely divergent characteristics, such as clay and chalk or sand, drawn from different sources, are to be used in the embankment they shall be depoSited in alternate layers of the same material over the full width of the embankment to depths approved by the Engineer. Rock, clay or other material shall be broken up, and no accumulation of lumps or boulders in the embankment will be permitted. No surplus material shall be permitted to be left at the toe of the embankment or at the top of cut Sections.
(viii) Side slopes shall be neatly trimmed to the lines and slopes shown on the drawings or as directed by the Engineer, and the finished Work shall be left in a neat and acceptable condition to the Engineer.