Methodology of Embankment Construction
The main component of every earthwork is the embankment. They are extensively utilized, for example, as reservoir embankment dams, road, railway, and airport runway embankments in transportation, but we are talking sequence-wise safe working method statement for embankment in earthwork for highway projects here.
Table of Contents
Work Scope
The work shall consist of constructing an embankment with approved and specified materials obtained from approved borrow areas or suitable material obtained from the roadway and drain excavation in accordance with the project specification.
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Reference
Road Transport and Highway Specifications for Roads and Bridges Technical Specification
Relevant contract drawings
Setting Out
Following completion of site clearance, the embankment’s limits must be marked by installing pegs at regular intervals on both sides. Outside the limits of construction areas, chainage boards and work benchmarks must be placed.
Materials and Borrowing Areas Selection:
Material
Embankment material shall be soil, moorum, gravel, a mixture of these, or any other material approved by the Engineer. It must be free of logs, stumps, roots, trash, and other material jeopardizing the structure’s stability.
The embankment material shall be obtained from an approved source, with preference given to material available from nearby roadway excavation or any other excavation under the contract.
The material requirements must be in accordance with the project specifications.
Borrow Material
Samples should be gathered from the identified borrow area and tested according to the requirements for suitability in embankment use according to project specifications. Following confirmation of the suitability of the material, the area must be adequately marked and meet the requirements.
Equipment
For the Embankment Construction, the following equipment shall be carried out. If desired, the contractor shall demonstrate the efficacy of the type of equipment to be utilized prior to the commencement of work.
Tipper Trucks
Hydraulic Excavator
Dozer
Dumper
Survey Kit / Instrument
Motor Grader
Soil Compactor
Water Tanker
Tractor
Trolleys
Operation Method
Before beginning earthwork, the limits of the embankment must be marked by placing pegs at regular intervals following site clearance. The construction toe line must be greater than the design toe line for correct edge construction.
The original ground must be leveled to allow for the installation of the first layer of the embankment, scarified, mixed with water, and then compacted by rolling to satisfy the minimum dry density specified in the updated technical specification.
The foundation treatment specified for embankments must be carried out in accordance with the approved drawing. Unsuitable material in the embankment foundation shall be removed in accordance with the Engineer’s direction and permission and shall be replaced by approved materials stacked in layers and appropriately compacted to the required and specified degree of compaction.
Excavation in approved borrow areas must be carried out with an excavator, and excavated material must be transported using dumpers or tractor trolleys.
The suitability of natural ground soil will be tested. It must be replaced with the Engineer’s authorization if found unsuitable.
The dry density of natural ground soil shall be determined, and the natural ground shall be tested for dry density; if less than 95% of M.D.D. is found, the original ground shall be scarified, mixed with the required amount of water, and compacted by vibratory roller to achieve the minimum specified dry density.
A continuous horizontal benching 300 mm broad or as per drawing shall be provided in the existing embankment for construction adjacent to the existing embankment.
The embankment material shall subsequently be dispersed in layers not exceeding 250 mm compacted thicknesses with the dozer over the entire area, followed by a motor grader.
Uninterrupted horizontal benches must be cut into the initial slope when widening an existing embankment to ensure appropriate connection. Where water is required to be added, it shall be sprinkled uniformly on the surface but without flooding from a water tanker equipped with a sprinkler and completely mixed in soil by harrowing until the uniform moisture content is obtained throughout the depth of the layer.
If the material transported to the roadbed is excessively wet, it must be dried by aeration and sun exposure until the moisture level may be accepted for compaction. During compaction, the moisture content should be within +/- 12 of OMC.
Vibratory Rollers weighing 8 to 10 tonnes must be used for compaction. Compaction trials on an appropriate stretch shall be carried out to establish the number of passes required for a specific type of soil dumped for an embankment to attain densities specified by the technical specification.
Actual compaction will be carried out based on the trial with the required number of passes of the Soil Compactor until the specified density is achieved.
Rolling must parallel the road’s center line, uniformly overlapping each preceding track by one-third of width. Rolling must be continued until the density specified is achieved. The soft area action must be removed and replaced with approved material if required compaction is not achieved.
Densities must be tested using the sand replacement method or a nuclear density gauge.
Subsequent layers shall be placed only after the finished layer has been tested and accepted. The top levels of the embankment must be examined with reference to the longitudinal and transverse profile of the road, as shown on the drawing, to ensure that the deviation is within the tolerance limit specified.
The various embankment layers will be marked on pillars installed outside the toe-line.
Quality Assurance
For embankment layers, the minimum compaction is 95% of the modified proctor value.
Workplace Safety
Adequate safety and traffic signs shall be provided adjacent to the road shoulders during the construction of widening works to protect the ongoing works in accordance with the location-specific safety plan.
In sites where tippers dump embankment materials from the road shoulder, a minimum of two flagmen with reflective vests and a red flag each must be deployed to control traffic that may be affected by the unloading operation.
All places near existing roads where embankment construction is underway must provide safe road signs.
No machines or equipment shall be allowed to stay unattended on the existing road or shoulder at all times unless fully protected and secured in a safe way.
The Safety Officer must make frequent patrols along the roadway to ensure that all safety equipment and signage are operational.
Trucks sometimes roll over tip heads because the driver backs over the edge or the edge collapses under the truck’s weight. A berm or timber balk should be used for protection. In order to avoid this danger, a signalman should be deployed.
When excavating trenches, keep the excavated material at least 600 mm far from the edge, where it cannot fall back into or collapse the trench wall.
Environmental Protection
a. Nearby streams, water courses, lakes, and reservoirs must be safeguarded from contamination caused by soil erosion from excavation areas by erecting temporary berms, dykes, sediment basins, slopes, drains, and using temporary mulches, seeding, or other control measures.
b. Vehicle tracks must be kept moist to prevent dust particles from flying while the vehicle moves.
tag: Method Statement for Embankment