Introduction
1.
The
Field Dry Density (FDD) Test is used to check the compaction level of
soil at site. It determines the in-situ dry density and compares it with the
maximum dry density from laboratory tests to ensure required compaction
(usually about 95% as per IS 2720).
This
test helps ensure the strength, stability, and durability of earthworks,
foundations, and pavements.
Today explain in very simple way I hope this is help to site Engineer, quality
engineer, Billing engineer.
What is Field Dry Density FDD Test
It is a simple and reliable field Dry density test on site soil compaction
We compare this site density with the maximum density from lab tests to see
whether proper compaction is achieved usually about 95% as per IS 2720.
FDD test Simple Understanding
Take soil Sample
Measure Weight
Check moisture content
Calculate density of soil
Verify compaction not less then 95% compaction result is pass
below 95% compaction failed
And As your Project specification.
Measure Weight
Check moisture content
Calculate density of soil
Verify compaction not less then 95% compaction result is pass
below 95% compaction failed
And As your Project specification.
Where it is used
Road Subgrade and sub base
Building foundation soil back filling
Embankment and earthwork
Ensure filling soil 200MM layer wise
required test each layer
Use of MDD in FDD Test
Building foundation soil back filling
Embankment and earthwork
Ensure filling soil 200MM layer wise
required test each layer
Use of MDD in FDD Test
MDD (Maximum Dry Density) is used as a reference value to check
the quality of compaction done on site using FDD (Field Dry Density).
To check compaction quality
MDD = Maximum density achieved in the lab
FDD = Field Dry Density achieved at site.
To check compaction quality
MDD = Maximum density achieved in the lab
FDD = Field Dry Density achieved at site.
1. To calculate percentage compaction
Compaction (%)
= (FDD / MDD) X 100
Example:
MDD
= 1.90 g/cc
FDD
= 1.80 g/cc
Compaction
= (1.80 / 1.90) × 100 = 94.7%
Required compaction is usually ≥ 95% of MDD
Field Dry Density Test (Core Cutter Method) – Procedure
1. Preparation
of Subgrade / Sub Base
Core Cutter Placement
Place the core cutter vertically on the prepared
surface and drive it into the soil using a rammer or hammer, ensuring minimum
disturbance.
Extraction of Core Cutter
Carefully excavate around the cutter and lift it out
without disturbing the soil sample inside.
Trimming of Soil Sample
Trim the excess soil from both ends of the core cutter
so that the soil is perfectly flush with the edges (no extra soil).
Weighing of Soil with Core
Cutter
Weigh the core cutter along with the soil sample and
record the reading.
Weighing of Empty Core Cutter
Empty the soil and clean the cutter. Then weigh the
empty core cutter and record the weight.
Collection and Mixing of Soil
Sample
Take the extracted soil and mix it thoroughly to
obtain a uniform sample.
Moisture Sample Preparation
Take approximately 5 grams of soil for moisture
content determination.
Filling in Rapid Moisture
Meter
Place the soil sample into the rapid moisture meter.
Addition of Reagent
Add the required quantity of calcium carbide (or
carbon chloride as per your method) into the moisture meter.
Shaking Process
Seal the device properly and shake it vigorously for
at least 2 minutes to ensure complete reaction.
Recording of Moisture Content
Note the moisture
content reading carefully from the rapid moisture meter.
Field Dry Density calculation
Determination
of Dry Density of Soil by Core Cutter Method
Test Method: IS 2720 (Part 29)
Given Below
Core
Cutter No 01
Weight
of Core Cutter + Wet Soil ( Ws ) in gms 2890
Weight
of Core Cutter (Wc) in gms (Core Cutter only) 900
Wet Soil=Ws−Wc
Example (1st reading)
2890−900=1990 gms
Weight of Wet Soil (Ws − Wc) in gms 1990
Volume of Core Cutter (Vc) in cubic cm 1021
Formula:
Yb
= (Ws−Wc ) / Vc
Example:
Yb=
( 1990 / 1021 ) = 1.94 gm/cc
Bulk Density (Yb) = (Ws − Wc) / Vc gm/cc
1.94
Moisture Content (M in %) by RMM Method 12
Dry Density (Yd)
Formula:
Yd
= ( 100 X Yb ) / (100+M )
Example (1st reading):
Yd
= ( 100×1.94 ) = 194
( 100+12 ) = 112
answer ( 194 / 112 ) = 1.73 gm/cc
Dry Density (Yd) = 100Yb / (100 + M) gm/cc 1.73
Maximum Dry Density (Yd) in Lab gm/cc 1.78
Optimum Moisture Content (OMC) 15.57
Field Compaction (%)
Formula:
Compaction
= (Yd X 100 ) / MDD×
Example (1st reading):
Compaction
= ( 1.73 X 100 ) 173
( 173 / 1.78 ) =
answer is 97.19 %
Field Compaction (%) = (Yd × 100) / MDD 97.19 %
1st Reading 97.19 %
2nd Reading 96.62 %
3rd Reading 97.19 %
Average = ( 97.19 + 96.62 + 97.19 ) = 291
= 291 / 3 final result is 97 % pass
Conclusion
Field Dry Density (FDD) test is an essential quality control test used to verify soil compaction at site. By comparing field dry density with maximum dry density (MDD), engineers can ensure that the required compaction level is achieved for stability and durability of structures. Proper testing and accurate recording help maintain construction quality and prevent future settlement issues.
Compaction (%)
= (FDD / MDD) X 100
Example:
MDD
= 1.90 g/cc
FDD
= 1.80 g/cc
Compaction
= (1.80 / 1.90) × 100 = 94.7%
Required compaction is usually ≥ 95% of MDD
Field Dry Density Test (Core Cutter Method) – Procedure
1. Preparation
of Subgrade / Sub Base
Core Cutter Placement
Place the core cutter vertically on the prepared surface and drive it into the soil using a rammer or hammer, ensuring minimum disturbance.
Extraction of Core Cutter
Carefully excavate around the cutter and lift it out without disturbing the soil sample inside.
Trimming of Soil Sample
Trim the excess soil from both ends of the core cutter so that the soil is perfectly flush with the edges (no extra soil).
Weighing of Soil with Core Cutter
Weigh the core cutter along with the soil sample and record the reading.
Weighing of Empty Core Cutter
Empty the soil and clean the cutter. Then weigh the empty core cutter and record the weight.
Collection and Mixing of Soil Sample
Take the extracted soil and mix it thoroughly to obtain a uniform sample.
Moisture Sample Preparation
Take approximately 5 grams of soil for moisture content determination.
Filling in Rapid Moisture Meter
Place the soil sample into the rapid moisture meter.
Addition of Reagent
Add the required quantity of calcium carbide (or carbon chloride as per your method) into the moisture meter.
Shaking Process
Seal the device properly and shake it vigorously for at least 2 minutes to ensure complete reaction.
Recording of Moisture Content
Note the moisture content reading carefully from the rapid moisture meter.
Core Cutter Placement
Place the core cutter vertically on the prepared surface and drive it into the soil using a rammer or hammer, ensuring minimum disturbance.
Extraction of Core Cutter
Carefully excavate around the cutter and lift it out without disturbing the soil sample inside.
Trimming of Soil Sample
Trim the excess soil from both ends of the core cutter so that the soil is perfectly flush with the edges (no extra soil).
Weighing of Soil with Core Cutter
Weigh the core cutter along with the soil sample and record the reading.
Weighing of Empty Core Cutter
Empty the soil and clean the cutter. Then weigh the empty core cutter and record the weight.
Collection and Mixing of Soil Sample
Take the extracted soil and mix it thoroughly to obtain a uniform sample.
Moisture Sample Preparation
Take approximately 5 grams of soil for moisture content determination.
Filling in Rapid Moisture Meter
Place the soil sample into the rapid moisture meter.
Addition of Reagent
Add the required quantity of calcium carbide (or carbon chloride as per your method) into the moisture meter.
Shaking Process
Seal the device properly and shake it vigorously for at least 2 minutes to ensure complete reaction.
Recording of Moisture Content
Note the moisture content reading carefully from the rapid moisture meter.
Field Dry Density calculation
Determination of Dry Density of Soil by Core Cutter Method
Test Method: IS 2720 (Part 29)
Given Below
Core Cutter No 01
Weight of Core Cutter + Wet Soil ( Ws ) in gms 2890
Weight of Core Cutter (Wc) in gms (Core Cutter only) 900
Wet Soil=Ws−Wc
Example (1st reading)
2890−900=1990 gms
Weight of Wet Soil (Ws − Wc) in gms 1990
Volume of Core Cutter (Vc) in cubic cm 1021
Formula:
Yb = (Ws−Wc ) / Vc
Example:
Yb= ( 1990 / 1021 ) = 1.94 gm/cc
Bulk Density (Yb) = (Ws − Wc) / Vc gm/cc 1.94
Moisture Content (M in %) by RMM Method 12
Dry Density (Yd)
Formula:
Yd = ( 100 X Yb ) / (100+M )
Example (1st reading):
Yd = ( 100×1.94 ) = 194
( 100+12 ) = 112
answer ( 194 / 112 ) = 1.73 gm/cc
Dry Density (Yd) = 100Yb / (100 + M) gm/cc 1.73
Maximum Dry Density (Yd) in Lab gm/cc 1.78
Optimum Moisture Content (OMC) 15.57
Field Compaction (%)
Formula:
Compaction = (Yd X 100 ) / MDD×
Example (1st reading):
Compaction = ( 1.73 X 100 ) 173
( 173 / 1.78 ) = answer is 97.19 %
Field Compaction (%) = (Yd × 100) / MDD 97.19 %
1st Reading 97.19 %
2nd Reading 96.62 %
3rd Reading 97.19 %
Average = ( 97.19 + 96.62 + 97.19 ) = 291
= 291 / 3 final result is 97 % pass
Conclusion
Field Dry Density (FDD) test is an essential quality control test used to verify soil compaction at site. By comparing field dry density with maximum dry density (MDD), engineers can ensure that the required compaction level is achieved for stability and durability of structures. Proper testing and accurate recording help maintain construction quality and prevent future settlement issues.
Determination of Dry Density of Soil by Core Cutter Method
Test Method: IS 2720 (Part 29)
Given Below
Core Cutter No 01
Weight of Core Cutter + Wet Soil ( Ws ) in gms 2890
Weight of Core Cutter (Wc) in gms (Core Cutter only) 900
Wet Soil=Ws−Wc
Example (1st reading)
2890−900=1990 gms
Weight of Wet Soil (Ws − Wc) in gms 1990
Volume of Core Cutter (Vc) in cubic cm 1021
Formula:
Yb = (Ws−Wc ) / Vc
Example:
Yb= ( 1990 / 1021 ) = 1.94 gm/cc
Bulk Density (Yb) = (Ws − Wc) / Vc gm/cc 1.94
Moisture Content (M in %) by RMM Method 12
Dry Density (Yd)
Formula:
Yd = ( 100 X Yb ) / (100+M )
Example (1st reading):
Yd = ( 100×1.94 ) = 194
( 100+12 ) = 112
answer ( 194 / 112 ) = 1.73 gm/cc
Dry Density (Yd) = 100Yb / (100 + M) gm/cc 1.73
Maximum Dry Density (Yd) in Lab gm/cc 1.78
Optimum Moisture Content (OMC) 15.57
Field Compaction (%)
Formula:
Compaction = (Yd X 100 ) / MDD×
Example (1st reading):
Compaction = ( 1.73 X 100 ) 173
( 173 / 1.78 ) = answer is 97.19 %
Field Compaction (%) = (Yd × 100) / MDD 97.19 %
1st Reading 97.19 %
2nd Reading 96.62 %
3rd Reading 97.19 %
Average = ( 97.19 + 96.62 + 97.19 ) = 291
= 291 / 3 final result is 97 % pass
Conclusion
Field Dry Density (FDD) test is an essential quality control test used to verify soil compaction at site. By comparing field dry density with maximum dry density (MDD), engineers can ensure that the required compaction level is achieved for stability and durability of structures. Proper testing and accurate recording help maintain construction quality and prevent future settlement issues.
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