Post on 19-Jul-2015
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