Excavation of Unsuitable Material and Back Fill With Suitable Material

EXCAVATION OF UNSUITABLE MATERIAL AND BACK FILL WITH SUITABLE MATERIAL

OBJECTIVE

To outline the work instruction by which the excavation of unsuitable material and backfill with suitable fill is carried out.


REFERENCES  

• MS ISO 9001 Clause 7.5.1
• BS 1377 Method of test for soils for Civil Engineering purposes

DEFINITIONS

Unsuitable material – shall include

i) running silt, peat, logs, stumps, perishable or toxic material, slurry or mud, or

ii) any material
- Consisting of highly organic clay and silt.
- Which is clay having a liquid limit exceeding 80% and / or a plasticity index exceeding 55%.
- Which is susceptible to spontaneous ignition.
- Which has a loss of weight greater than 2.5% on ignition.
- Containing large amounts of roots, grass and other vegetable matter.

iii) Suitable Material – shall mean those materials other than the unsuitable materials defined above.

MATERIALS

All Suitable Material / Earth Fill must have record of Proctor Test and Engineer to verify the soil characteristic so as it will suit with the existing earth at the excavated area.


HANDLING AND STORAGE OF MATERIALS

Handling : - Transport for material shall be carried out by dump trucks or other suitable machinery.
Storage : Suitable material / Earth fill must be protected and cover if not been use within 24 hours or as per environmental guideline.


PLANT, MACHINERY AND EQUIPMENT

Excavator, Lorries, Dozer, Compactor and Backpusher.


PREPARATORY WORKS

1. Obtain relevant approved construction drawing from client / client’s representatives.
2. Set out the location and limits of work.
3. Carry out Soil Investigation to determine the depth of unsuitable material and submit the results to the client / client’s representative for decision on depth of unsuitable material that needs to be replaced.
4. Carry out survey to obtain original ground level and submit to client / client’s representatives.
5. Identify and obtain approval for disposal site.

WORK METHODOLOGY

1. Prepare access to the working area and plan for the lorry and plant movements.
2. Excavate the unsuitable material to the required depth as specified by the client / client’s representative and dispose at approved disposal area.
3. Transport, fill and spread suitable material in layers. The loose for each layer of fill shall be determined from the trial compaction.
4. Repeat step 4 until the required level is achieved. Carry out necessary tests as per inspection & test plans :
• Compaction Trials : The BS 1377 Compaction test (4.5 kg rammer method) shall be used in determining the moisture contest versus density relation of soil.
•  Degree of compaction : The whole of the embankment below the top 300mm of the subgrade shall be compacted to not less than 90% (for cohesive material) or 95% (for cohesionless material) of the maximum dry density determined in the BS 1377 Compaction test (4.5 kg rammer method)
• Field Density Testing : Field density tests on each layer of compacted earth fill shall be carried out using sand replacement method in accordance with BS 1377.
• Moisture control : - Each layer of earth fill shall be processed as necessary to bring its moisture content to a uniform level throughout the material, suitable for compaction. The Optimum moisture content as determined by BS 1377 compaction test (4.5 kg rammer method) shall be used as a guide in determining the proper moisture content at which each soil type shall be compacted.
5. Submit request for inspection form for joint inspection and joint measurement with client / client’s representative using Earthwork Inspection checklist.
6. Request client / client’s representative to sign on checklists and maintain all inspection / approval records as per Project Filing Index.
7. Carry out computation and submit for claim.