EARTHWORK OF EXCAVATION IN FOUNDATION (Specification)

SCOPE

This specification covers the earthwork in excavation for all types of foundation wet & dry.

GENERAL

1. Contractor shall furnish all tools, plants, instruments, qualified supervisory personnel, labour, materials, any temporary works, consumable, any and everything necessary, whether or not such items are specifically stated

Here in for completion of the job in accordance with specification requirements.

2. Contractor shall carry out the survey of the site before excavation and set properly all lines and establish levels for various works such as earthwork in excavation for grading, basement, foundations, plinth filling, roads, drains, cable trenches, pipelines etc. Such survey shall be carried out by taking accurate cross sections of the area perpendicular to established reference/grid lines at 8 m intervals or nearer as determined by Engineer based on ground profile. These shall be checked by Engineer and thereafter properly recorded.

3. The excavation shall be done to correct lines and levels. This shall also include, where required, proper shoring to maintain excavation and also the furnishing, erecting and maintaining of substantial barricades around excavated areas and warning lamps at night for ensuring safety.

4. The rates quoted shall also include for dumping of excavated materials in regular heaps, bunds, riprap with regular slopes as directed by Engineer, within the lead specified and leveling the same so as to provide natural drainage. Rock/soil excavated shall be stacked properly as directed by Engineer. As a rule, all softer material shall be laid along the center of heaps, the harder and more weather resisting materials forming the casing on the sides and the top. Rock shall be stacked separately.

FILL, BACK FILLING AND SITE GRADING

 GENERAL

All fill materials will be subject to Engineer’s approval. If Engineer rejects any materials, Contractor shall remove the same forthwith from the site at no extra cost to the Owner. Surplus fill material shall be deposited/disposed off as directed by Engineer after the fill work is completed.

No earth fill shall commence until surface water discharges and streams have been properly intercepted or otherwise dealt with as directed by Engineer.

 MATERIAL

1. To the extent available, selected surplus spoils from excavated materials shall be used as backfill. Fill

materials shall be free from clods, salts, sulphates, and organic or other foreign material. All clods of earth shall be broken into pieces not larger than 150-mm size mixed with properly graded fine materials consisting of murrum or earth to fill up the voids and the mixture used for filling.

2. If any selected fill material is required to be borrowed; Contractor shall make arrangements for bringing such material from outside borrow pits. The material and source shall be subject to prior approval of Engineer. The approved borrow pit area shall be cleared of all bushes, roots of trees, plants, rubbish etc. top soil containing salts/ sulphates and other foreign materials shall be removed. The materials so removed shall be burnt or disposal off as directed by Engineer.

3. Contractor shall make necessary access roads to borrow areas and maintain the same, if such access road does not exist, at his cost.

FILLING IN PITS AND TRENCHES AROUND FOUNDATIONS OF STRUCTURES, WALLS ETC.

As soon as the work in foundations has been accepted and measured, the spaces around the foundations, structures, pits, trenches etc, shall be cleared of all debris, and filled with earth in layers not exceeding 45 cm., each layer being watered, rammed and properly consolidated, before the succeeding one is laid. Each layer shall be consolidated to the satisfaction of Engineer. Earth shall be rammed with approved mechanical compaction machines. Usually no manual compaction shall be allowed unless Engineer is satisfied than in some cases manual compaction by tampers cannot be avoided. The final backfill surface shall be trimmed and leveled to proper profile as directed by Engineer or indicated on the drawings.

PLINTH FILLING

1. Plinth filling shall be carried out with approved material as described above in layers not exceeding 45 cm,watered and compacted with mechanical compaction machines. Engineer may however permit manual compaction by hand tampers in case he is satisfied that mechanical compaction is not possible. When filling reaches the finished level, the surface shall be flooded with water, unless otherwise directed, for at least 24 hours, allowed to dry and then the surface again compacted as specified above to avoid settlements at a later stage. The finished level of the filling shall be trimmed to the level/slope specified.

2. Where specified in the schedule of works, compaction of the plinth fill shall be carried out by means of 12 tones rollers smooth wheeled, sheep-foot or wobbly wheeled rollers. A smaller weight roller may be used only if permitted by Engineer. As rolling proceeds water sprinkling shall be done to assist consolidation. Water shall not be sprinkled in case of sandy fill.

3. The thickness of each unconsolidated fill layer can in this case be up to a maximum of 450 mm. Engineer will determine the thickness of the layers in which fill has to be consolidated depending on the fill materials and equipment used.

4. Rolling shall commence from the outer edge and progress towards the centre and continue until compaction is to the satisfaction of Engineer, but in no case less than 10 passes of the roller will be accepted for each layer.

5. The compacted surface shall be properly shaped, trimmed and consolidated to an even and uniform gradient.

6. All soft spots shall be excavated and filled and consolidated.

At some location/areas it may not be possible to use rollers because of space restrictions etc. Contractor shall

then be permitted to use pneumatic tampers, rammers, etc. and he shall ensure proper compaction.

 SAND FILLING IN PLINTH AND OTHER PLACES

At places backfilling shall be carried out with local sand if directed by Engineer. The sand used shall be clean, medium grained and free from impurities. The filling-in-sand shall be kept flooded with water for 24 hours to ensure maximum consolidation. Any temporary work required to contain sand under flooded condition shall be to Contractor’s account. The surface of the consolidated sand shall be dressed to required level or slope.

Construction of floors or other structures on sand fill shall not be started until Engineer has inspected and approved the fill.

 FILLING IN TRENCHES

1. Filling in trenches for pipes and drains shall be commenced as soon as the joints of pipe and drains have been

tested and passed. The backfilling materials shall be properly consolidated by watering and ramming, takingdue care that no damage is caused to the pipes.

2. Where the trenches are excavated in soil, the filling from the bottom of the trench to the level of the centerline of the pipe shall be done by hand compaction with selected approved earth in layers, backfilling above the level of the centre line of the pipe shall be done with selected earth by hand compaction or other approved means in layers.

3. In case of excavation of trenches in rock, the filling up to a level 30 cm. above the top of the pipe shall be donev with fine materials, such as earth, murrum etc. The filling up of the level of the centerline of the pipe shall be done by hand compaction in layers. Whereas the filling above the centerline of the pipe shall be done by hand compaction or approved means in layer not exceeding 45 cms. The filling from a level 30-cm above the top of the pipe to the trench shall be done by hand or other approved mechanical methods with broken rock filling mixed with fine material as available to fill up the voids.

4. Filling of the trenches shall be carried simultaneously on both sides of the pipe to avoid unequal pressure on the pipe.

MEASUREMENT AND PAYMENT

1. Backfilling as per specification the sides of foundations of columns, footings, structures, walls, tanks, rafts, trenches etc. with excavated materials will not be paid for separately. It shall be clearly understood that the rate quoted for excavation including backfilling shall include stacking of excavated material as directed, excavation/packing of selected stacked material, conveying it to the place of final backfill, compaction etc. as specified. As a rule material to be backfilled shall be stacked temporarily within the basic lead of 100 meters unless otherwise directed by the Engineer. If Engineer directs/permits a lead of over 100 meters for such material, the conveyance of the material for the extra distance over the basic lead of 100 meters for backfilling will be paid for.

2. Payment for fill inside trenches, plinth or similar filling with selected excavated material will be made for only compaction as specified/directed. Cost of all other operations shall be deemed to have been covered in the rate quoted for excavation. Payment for this work will be made based on measurement of plinth/trench dimensions filled. The Plinth ground levels shall be surveyed before hand for this purpose. If no compaction is specified/desired such filling will not be separately paid for. In such an event the fill shall be leveled/finished to the profile as directed at no extra cost.

3. Backfilling, plinth filling etc. with borrowed earth will be paid for at rates quoted. The quoted rate shall include all operations such as clearing, excavation, lead and transport, fill, compaction etc. as specified.

4. Actual quantity of consolidated filling or actual quantity or excavation in the borrow pits (less such topsoil which has been excavation and not used for filling) whichever is less shall be measured and paid for in cubic meters. The lead, lift etc. shall be as indicated in the schedule of quantities.

5. Actual quantity of consolidated sand filling shall be measured and paid in cubic meters.