COMPACTION WORK
1. Name of Work & Description
Compaction work is required after the backfilling work of the foundation of the building or any structure from a hard surface. Compaction should be done in only
layers up to 300mm to 500mm for road, building, bridge foundation, etc.
Compaction of backfilling work is the most
important factor in the construction field. A lot of structures life depends on the compaction of backfilling material.
Types of using of Material Compaction Work.
1 Soft Soil
2 Murum (Same Gravels)
3 Murum (Brown Stone Color uniform size)
4 Murum (60-100mm size)
5 Boulders: Good Compaction is Not Possible
for Boulders
6 Debris: Good Compaction is Not Possible for
Debris, but if gravels size will be small, then it will be possible.
2. IS Code No.
IS Code for Methods of test for Soils: IS 2720:
Determination of water content- dry density relation using light compaction.
IS Code for Methods
of test for Soils: IS 10074: Compaction mold assembly for light and heavy
compaction test for soils
3. The Drawing Needs to Read.
Compaction work is part of
Backfilling work which required the same drawing
Following drawing need to
read before Compaction work.
1 Building
Foundation and Section Plan
2 Bridge
Embankment Foundation and Section Plan
3 Plinth
Section
4 Reduced
Level Plan of Existing Ground
5 Plot
Layout Drawing
6 Road
Level Top and Bottom
7. Road The section as per Ground Level
4. Location of Work
Compaction work can be done with the following Locations.
1 Building Foundation
2 Podium Foundation
3 Basement
4 Under Ground Water Tanks
5 Bridge Foundation
6 Culvert
7 Dam
8 Trench
9 Road
10 Bridge Embankment
11 KT Weir Embankment
5. Standard Procedure of Work (Step by Step)
Work Procedure before Start the Compaction
1 Read Plot Layout Drawing Carefully.
2 Calculate Approximate measurements
to get the idea of required backfill material.
3 If
compaction is proposed then 1.5 times the quantity of material is required to
backfill.
3 Read
Foundation drawing plan, where Footing and Raft of the building is outside then
building line.
4 Calculate
Outer to outer distance from foundation drawing of building or bridge
structure.
5 Do site
visit of Backfill material quarry. Please keep quarry distance nearest form
your site.
6 Finalize
material as per your requirement.
7 Finalize the
rate as per your budgeted amount for backfilling work.
8 Arrange the material for
testing of the Proctor density Test.
Work Procedure during the Compaction
1 Remove
all the Material from Pit, or Backfilling Area.
2 Fill
loose material with help of machine up to 300mm height.
3 Do not backfill murum more than 300mm.
4 Do not allow boulders in Backfill murum.
5 Do not allow any vegetation/twigs
6 Do not allow keep the boulders near RCC
structure, it can be damaged RCC member.
7 Compaction must be done by first filling the
excavated soils in layers of 300–500mm and tamping it with a vibrator. Till the desired level. The soil is moistened up to the optimum moisture content to
establish optimum compaction and best results.
8 Barricade
the area compaction area when machinery is working.
9 Check
and Note down backfilled area levels with help of an Auto level.
10
Proctor Density Tests should be done at each layer.
6. Checkpoints
1 Check
Machine Capacity, as well as which types of machinery, are required to
compaction work.
2 Instruct
to machine operator regarding the depth of Backfilling Material as well as the thickness of each layer.
3 Instruct
to Operator to compact each layer properly.
4 Compact
each layer of the earth not exceeding 200mm.
5 Earth/soil should be free of
vegetation/twigs if any.
6 Earth/soil should be free of boulders if
any.
7 Rolling should be done with a 5-ton mechanical
roller after sprinkling enough water and core cutter samples taken for every
150sq.m
8 Proceed to the next layer after achieving a minimum
of 95 % of MDD (maximum dry density).
9 Keep
all workers Safe distance from Machine.
10 Compaction
must be done by first filling the excavated soils in layers of 30–50 mm and
tamping it with a vibrator. Till the desired level. The soil is moistened up to the
optimum moisture content to establish optimum compaction and best results.
11 After completion
of compaction arrange the architect visit to inspect the level as per Sections.
Check the
Plinth Level and desired level before complete the backfilling, also keep down
the level of backfilling area for Soling, PCC & Flooring, or for Road work
keep the level down for WBM, Tack Coat, Seal Coat Etc.
12 Please
check Depth of Soling, PCC, Footing/Raft, and Plinth Beam before completing the
excavation.
For
Example: If Plinth Level is Given 1.0m
Above GL.
Then Calculate
Minimum Backfilling Depth
Soling for Footing:
0.23m
PCC for Footing: 0.15m
Tiling Work: 0.050m
Then Top Level of Compacted
Backfill Area is 0.57m below from Plinth Height.
7. Equipment and Machinery
There are two types of Compaction
is done
Manual Compaction
Manual Compaction
can be done with 250-1000kg Compactor can be used for Compaction, It will be too much costly and time
consumable. This process is using under the building, a small area of work,
etc.
Mechanical Compaction.
With the help of advance technology excavation is made too much easy and cost-effective
as well as time-saving.
Following The machine is using for excavation
1 Backhoe Loader (JCB)
2 Mini Excavator (Mini poclain, Bob-Cat)
3 Mini Compactor
4 Plate Compactor
5 Road Roller
6 Grader
7 Vibro Roller
8 Water Tanker
9 Dozer
10 Rammer
8. Measurement and Quantity Survey
For the Calculation of the backfilling
area and quantity of backfilled material, we need the following points.
1
Excavated ground level reading: Average level of each interval
2 Compacted
Ground Level Reading: Average level of each interval.
3 Actual compacted
Area: Prepare geometrical shapes as per level interval as we can find an exact compacted
area as well as the depth of the compacted backfilling area.
Depth of Compacted
Backfilling = RL of excavated GL – RL of compacted backfilled GL
Quantity
of Compacted Backfilled Area = Actual backfilled Area X Depth of compaction
Backfilling
Compaction Work Unit is Square Meter or Square Feet.
9. Checklist
Proctor Density Test Details
Test
Objective: To determine the required amount of water to be used when
compacting the soil in the field and the resulting degree of denseness; this
can be expected from compaction at optimum moisture content.
Apparatus:
1 Cylindrical
metal mold shall be either of 100mm diameter and 1000cm3 volume or 150mm
diameter and 2250cm3 volume and shall conform to IS 10074 – 1982.
2 Balance of
capacity 500grams and sensitivity 0.01gram.
3 Balance of
capacity 15Kg and sensitivity one gram.
4 Thermostatically
controlled oven with capacity up to 250degree celsius.
5 Airtight
containers.
6 Steel
straight edge about 30cm in length and having one beveled edge.
7 4.75mm, 19mm, and 37.5mm IS sieves confirming
to IS 460 (Part 1).
8 Mixing tools such as tray or pan, spoon,
trowel and spatula or suitable mechanical
9 device for
thoroughly mixing the sample of soil with additions of water.
10 Heavy
compaction rammer confirming to IS: 9189 -1979.
Procedure:
1 Take a representative sample of air-dried soil of about 5 kg (soil not susceptible to
crushing during compaction) or 3 kg from 15 kg sample (soil susceptible to
crushing during compaction) passing through 19mm IS sieve and mix thoroughly
with a suitable amount of water depending on the type of soil, generally 4 to 6
percent for sandy and gravelly soils and plastic limit minus 8% to 10% for
cohesive soils.
2 For soils
susceptible to crushing during compaction take different samples for every
determination and for soils not susceptible to crushing during compaction use
the same sample for all the determinations.
3 Weigh the
1000cc capacity mold with the base plate attached and without extension to the nearest gram (m1). 4 Place the mould on a solid base such as a
concrete floor or plinth and compact the moist soil into the mold, with the
extension attached in 5 layers of approximately equal mass, each layer being
given 25 blows with the 4.90kg hammer dropped from a height of 450mm above the
soil.
5 Distribute
the blows uniformly on each layer.
6 The amount
of soil used shall be sufficient to fill the mold leaving not more than about
6mm to be struck off when the extension is removed.
Compaction
of soil into the mold
7 Remove the
extension and carefully level the compacted soil to the top of mould by means
of the straight edge.
8 Weigh the
mould and the soil to the nearest gram (m2). Remove the compacted soil from the
mold and place on the mixing tray.
9 Collect a
representative sample from the soil in the tray and keep in the oven for· 24 hours maintained at a
temperature of 1050 to 1100 C to determine the moisture content (W).
Compacting
soil containing coarse material up to 37.50 mm size
10 Take
representative sample of material passing through 37.50 mm IS sieve.
11 Compact
the material in 2250 cm3 volume of mold in five layers each layer being given
55 blows with 4.90 kg rammer dropped from a height of 450mm above the
soil.
12 The
remaining procedure is the same as described above for 1000cc mold.
13 In all
the above cases make at least five determinations and the range of moisture
content shall be such that the optimum moisture content at which the maximum
dry density occurs is within that range.
CALCULATIONS
Calculate
the bulk density gw in
g / cm3g of each compacted specimen from the equation,
gw
= (m2 – m1) / Vm
m1 = Weight
of the mould with base plate.
m2 = Weight
of the mould with compacted soil.
Vm = Volume
of mold in cm3.
Calculate
the dry density gd in
g/cm3 from the equation,
gd =gw / (1+W/100)
g
w = Bulk density
W = % of moisture content
REPORT
1 Plot the
values obtained for each determination on a graph representing moisture content
on the x-axis and dry density on the y-axis.
2 Draw a
smooth curve through the resulting points and determine the position of the
maximum in the curve.
3 Report the
dry density corresponding to the maximum point to the nearest 0.01.
4 Report the
percentage corresponding to the maximum dry density i.e. optimum· moisture content to the
nearest 0.2 %for values below 5% and to the nearest 0.5% for values from 5 to
10% and to the nearest whole number for values exceeding 10 %.
PRECAUTION
With clays
of high plasticity or where hand mixing is employed, it may be difficult· to distribute the
moisture uniformly throughout the air-dried soil by mixing alone, So it may be
necessary to preserve the mixed sample in a sealed container for a minimum
period of about 16 hours before conducting the test.
10. On-site Experience
Readers Experience: In our industrial project in during the execution
our work tender is only RCC and Structural work, and Excavation and backfilling
in Client scope, so after completion of the footing of the industrial building they
backfilled the loose material and compaction is not done properly due to less
time. But from this plot old nalla is passed, and there is muddy soil up to 6m
from ground level, but due to not proper compaction and not proper execution
done by earthwork contractor our building area trimix floor is going down up to
600mm after completing all the work. So please do proper compaction otherwise
it may be more costly than your budget.
Mr. Riyaz (Engineer)
Team
CBEC India
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