Lecture 4 – BackfillingLecture 4 – BackfillingObjectives:-

1.To learn the backfill to existing structures.2.To relate the backfilling as per clauses in SMM23.To determine the various clauses applied to the backfilling

Outcomes:-1.Able to differentiate the different clauses used for backfilling2.Able to write down the dimensions clearly.

BackfillingBackfilling

It is an activity immediately after It is an activity immediately after excavation work.excavation work.

This activity needs a lot of thinking This activity needs a lot of thinking and imagination.and imagination.

Once we have excavated the soil Once we have excavated the soil what next?what next?

Fig. 1 Excavated pit Fig 2. Excavated pit with footing and stump

Then what ?Then what ?

Fig.1 Plan of a footing

Fig.2 Section of a footing

We need to backfill

After backfill what next?After backfill what next?

A

B

Total excavated material( A + B = C) so A is the backfill quantity while C – A = B ( Qty. to be removed)

Lets look at a simple structureLets look at a simple structure

F1 (1.00m x 1.00m )

Ground beam 150mm x 450mm

Stump 150mm x 150mm

Plan of a Guard house

Testing your eye sightTesting your eye sight

View A

View B

View A

View B

GB1

GB2 GB3

GB4

GB1

GB4GB3

Before excavation we need to know Before excavation we need to know the different activities involvedthe different activities involved

11stst. Measure the oversite . Measure the oversite excavation with average depth of excavation with average depth of

150mm150mm5.00m

5.00m

Area of oversite excavationArea of oversite excavation5.00m

5.00m

Excavate for footingExcavate for footing

Section of excavationSection of excavationGround level Base of footing level

Lets put in the structureLets put in the structure

Oversite excavation average Oversite excavation average 150mm thick150mm thick

Lets add in a ground floor slabLets add in a ground floor slab

Slab 100mm thick

Lets look at the isometric view of Lets look at the isometric view of the structurethe structure

Grd. Beam

Grd. Floor slab

Stump

Footing

Look at the sequence carefullyLook at the sequence carefully

A B C D

So when you measure backfill you So when you measure backfill you shall consider carefully the different shall consider carefully the different

depth for the different areadepth for the different area

Area 1

Area 2

Area 3 Area 4

Plan view of footing

Description for excavation, backfill and Description for excavation, backfill and removal.removal.

Excavate pit for footing Excavate pit for footing commencing from ground level commencing from ground level with plan dimension less than with plan dimension less than 1.25m and with depth not 1.25m and with depth not exceeding 2.00m (5 nos.)exceeding 2.00m (5 nos.)

Selected backfill to required Selected backfill to required formation level, spread, levelled formation level, spread, levelled and well rammed and and well rammed and consolidated.consolidated.

Removing surplus excavated Removing surplus excavated material from site including material from site including transporting to contractor’s own transporting to contractor’s own tip.tip.

Description for oversite Description for oversite excavationexcavation

Oversite excavation average 200mm Oversite excavation average 200mm thick including transporting top soil thick including transporting top soil to site to be determined by the to site to be determined by the architect for re-use.architect for re-use.

Oversite excavation commencing Oversite excavation commencing from ground level to a depth not from ground level to a depth not exceeding 250mm.exceeding 250mm.

Exercise no. 1: measure the backfill Exercise no. 1: measure the backfill quantity using the description quantity using the description

providedprovided

Footing F1 ( 12 nos.)

1000mm

1000mm

1.85m

650mm

Stump 300mm x 300mm

Exercise no. 2- Measure the backfill Exercise no. 2- Measure the backfill to footing F2to footing F2

900mm

900mm

F2 ( 20 nos.)

1.65m

450mm

Stump 150mm x 150mm

Grd. Beam 125mm x 450mm

125mm

450mm

Section of ground beam

Exercise no. 3 – Measure the Exercise no. 3 – Measure the following:following:

1. Oversite excavation to footing F1.1. Oversite excavation to footing F1. 2. Excavation to Footing F1.2. Excavation to Footing F1. 3. Backfilling to Footing F1.3. Backfilling to Footing F1. 4. Removing surplus earth of footing 4. Removing surplus earth of footing

F1.F1. 5. Write down your answer in the 5. Write down your answer in the

correct format with correct correct format with correct description.description.

Footing F1 ( 25 nos.)Footing F1 ( 25 nos.)

950mm

950mm

GL

Oversite excavation 150mm depth

2.00m

50mm lean concrete

Stump 250mm x 250mm

450mm

GB 250mm x 600mm

PlanSection