Methodology for Embankment Construction

Scope of Work

The work shall consist of the construction of embankment with approved and specified materials obtained from approved borrow areas or suitable material obtained from roadway and drain excavation, in accordance with Clause 305 of MoRTH specifications.

Reference

• Contract Agreement
• IRC: SP: 84-2014
• Ministry of Road Transport & Highways Specifications (MoRTH - 5th Revision)
• Relevant Drawings

Setting Out

After completion of site clearance, the limits of embankment shall be marked by fixing pegs on both sides at regular intervals. Chainage boards and working bench marks shall be established outside the construction area limits for accurate reference.

Selection of Material and Borrow Areas

Material

The material used in embankment shall be soil, moorum, gravel, reclaimed material from pavement, fly ash, pond ash, or a combination approved by the Engineer. It must be free from logs, roots, rubbish, and any deleterious matter that could affect embankment stability. Preference shall be given to material available from roadway or structure excavation within the project limits. The material shall conform to the requirements of Clause 305.2 of MoRTH Specifications.

Borrow Material

The borrow material used for embankment or subgrade construction shall comply with Clause 305.2.2.2 and Clause 903.2 of MoRTH. Materials must be tested and verified for suitability before use, ensuring compliance with grading, plasticity, and compaction standards. Test results should confirm that the borrow material meets the requirements for optimum moisture content (OMC), maximum dry density (MDD), and California Bearing Ratio (CBR) prior to approval.

Material Testing & Frequency

Sl. No.	Item	Reference Code	Frequency
1.1	Sand Content / Gradation	IS:2720 (Part 4), MoRTH Clause 903.2	2 Tests / 3000 m³
1.2	Atterberg’s Limits	IS:2720 (Part 5), MoRTH Clause 903.2	2 Tests / 3000 m³
1.3	Modified Proctor Test (MDD & OMC)	IS:2720 (Part 8), MoRTH Clause 903.2	2 Tests / 3000 m³
1.4	Moisture Content	IS:2720 (Part 2)	1 Test / 250 m³
1.5	CBR Test for Subgrade	IS:2720 (Part 16), MoRTH Clause 903.2	1 Test / 3000 m³
1.6	Free Swell Index Test	IS:2720 (Part 40), MoRTH Clause 903.2	1 Test / 3000 m³

Equipment

The following equipment shall be used for the construction of embankment as per MoRTH Clause 305:

• Hydraulic Excavator
• Dozer
• Dumper (Tipper Trucks)
• Motor Grader
• Vibratory Roller (8–10 tonne)
• Water Tanker with sprinkler
• Tractor Trolleys
• Survey Kit / Instruments

Method of Operation

1. Setting Out and Preparation: After site clearance, mark embankment limits with pegs. Keep construction toe line slightly beyond design toe line for proper compaction along edges.
2. Preparation of Original Ground: Level the original ground, sprinkle water, and compact using rollers to achieve minimum dry density. Remove unsuitable soil and replace with approved material in layers compacted to specification.
3. Testing of Natural Ground: The natural ground shall be tested for suitability. If the in-situ dry density is found to be less than 95% of MDD, the surface shall be scarified, moisture content adjusted to OMC, and re-compacted until the specified density is achieved.
4. Spreading of Embankment Material: Spread material in layers: 250 mm for vibratory roller, 200 mm for static roller. Use dozer and grader. For widening, cut benches into old slope for bonding.
5. Moisture Conditioning: Add water using sprinklers and mix with rotavator or grader until uniform near OMC. Over-wet material should dry before compaction.
6. Compaction: Use vibratory (8–10 t) or static roller depending on soil type. Prepare trial section to determine number of passes. Roll in parallel passes overlapping one-third of roller width. Field test density with Sand Replacement Method (IS 2720 Part 28).
7. Subsequent Layers: Place new layers only after previous layer is tested and accepted. Top levels must conform to approved drawings; maintain tolerances per Table 900-1 of MoRTH.

Key Quality Control Points

• Field density ≥95% for embankment, 97% for subgrade.
• Moisture within ±2% of OMC.
• Maintain layer thickness uniformity using grader and survey checks.
• Perform compaction trials for rolling pattern and passes.
• Field density tested every 500 m² per layer.
• Ensure side slope protection and drainage before next layer.