Field Dry Density Test (FDT) By Sand Replacement Method - ASTM D 1556 And ASTM D 1557

Method For Field Dry Density Test (FDT) By Sand Replacement Method ( Using a Sand Cone Apparatus) 

ASTM D 1556 ASTM D 1557 BS 1377

Dear friends this is a very important test at the site. The fresher engineer must read the full post and shall learn about this test, I have shared in detail about this test if any doubt just comments below.

1.0 SCOPE 

1.1 - This method statement detail the procedure for determining the in-place density and unit weight of soil by using a sand cone apparatus for granular sub-base, subgrade, ABC  ( Aggregate base course), Structural fill Material.  

1.2 - This method is not suitable for soils that would deform or compress during the excavation of the test pit and also not suitable for soils contains an appreciable amount of oversize particles.

2.0 PURPOSE 

2.1 - The purpose of the test is to provide data to assist in the evaluation of soil placed as an engineering soil (embankments, foundation, pads, road bases) of foundation soil often compacted to improve their engineering properties. This test method of conjunction with ASTM D 1557 ( Laboratory compaction characteristics of the soil) can be used to determine the degree of relative compaction and the % of water content achieved at the site.

2.2 - This test method can be used as a basis for the quality control acceptance for soil compacted to a specified density or percentage of a maximum density determined by a laboratory test method such as ASTM D 1557.

3.0 REFERENCE DOCUMENTS 

3.1 - ASTM D 1556

3.2 - ASTM D 1557

3.2 - ASTM D 2216

3.3 - BS - 1377 PART - 4 

3.4 - PROJECT SPECIFICATION

4.0 APPARATUS 

Sand Cone Apparatus 

4.1 - Density Apparatus - shall consist of a plastic jar and a detachable appliance consisting of a cylindrical valve with an approximately 13mm dia. Orifice and having a small funnel on one end which can be attached to the plastic jar and a large funnel on the other end.

4.2 - A metal base plate with a flanged center hole ( 15cm dia for 150mm layer and 20cm dia hole for above 150mm)  to receive the large funnel.

4.3 - Clean, dry, Uniform in density and grading, and free-flowing sand.

4.4 - Weighing Balance - having an accuracy of 0.1 % of the total mass used for weighing.

4.5 - Drying Oven - Thermostatically controlled and capable of maintaining a uniform temperature of 110 ± 5 ˚C.

4.6 - Specimen Containers - Non-corrosive metal containers with close-fitting lids for moisture content determination.

4.7 - Miscellaneous Equipment - Chiesel, Hammer, Small Paint Brush, Plastic Bags for retaining the moist soil sample, large nails to securing the base plate, etc.

Sand Cone Apparatus for 30 cm Thick layer

5.0 INSPECTION AND CALIBRATION OF APPARATUS 

5.1 - Sand in cone apparatus will be checked on a 14 working days basis.

5.2 - Sand cone apparatus will be routinely inspected for damage that may affect the volume of the cone will necessitate a recalibration.

5.3 - Determination of density of sand will be done on a 14 working days basis or any significant changes in atmospheric humidity or before the use of a new batch of sand.

5.4 - Prior to starting the test all apparatus shall be checked and the calibration sticker shall be checked at the test location.

6.0 PROCEDURE 

6.1 - Prior to starting the test Maximum dry density (MDD) and Optimum Moisture Content shall be available.  Note: - Using former MDD and OMC value is considered as Non-Comformace so Site QC shall mark it that new MDD and OMC are used and frequency for MDD and OMC shall be followed as per project specification. ( Generally One test for MDD and OMC for each 5000 Cum loose-filled material).

6.2 - The selection of test locations is done by the client or consultant. 

6.3 - Numbers of the test is done by as per project specification frequency ( Generally one test for each 400 Sqm or if compaction is done separately for each area so each test for compaction).

6.4 - Level the surface of the test location by using the base plate, seat the base plate on the plane surface if required used nails to secure the plate against any moment while doing the test.

Procedure for FDT and Apparatus 

6.5 - Dig the test hole through the center hole of the base plate. The volume shall depend on the anticipated maximum particle size and in any case more than 1415cm2. (Or hole dept approximately 12cm to 15cm).

6.6 - Place all excavated soil, and any loosened soil while digging in a plastic bag and seal it with masking tape for preventing any loss of moisture until the wet soil mass has been determined in the laboratory.

6.7 - Invert the previously weighed sand cone apparatus on the cleaned flanges of the base plate, Avoid all types of vibrations in the test area. Open the valve and allow the sand to fill the test hole and the sand cone. Close the valve when the flowing of the sand stopped.

6.8 - Determine the mass of moist soil at the laboratory, check for any oversize. If present use the oversize correction if required.

6.9 - Determine the moisture content in accordance with ASTM D 2216

6.10 - Determine the mass of remaining sand and calculate the volume of the excavated hole.

6.11 - Calculate the in place wet and dry density of the material tested.

6.12 - Calculate the in-place dry unit weight.

6.13 - Determine the in place relative compaction by using the laboratory determined maximum dry density.

7.0 REPORTING 

The calculation for wet dry density, moisture content, and dry density shall be done as per the below calculation.
 The dry density of compacted soil will be found in Three steps as calculated below.

IN-PLACE WET DENSITY OF SOIL

1. Bulk density of poured Sand  (ρs) g/m3 - 1.48 ( Varies from 1.47 to 1.52, Based on the result in test, Bulk density shall be regularly checked in the period of 14 days)
2. The initial mass of sand before pouring (m1) in g = 8000 gm ( with the bottle ).
3. Mass of sand after pouring in the hole (m2) in g = 2940 gm 
4. Mass of sand used to fill Funnel and Baseplate (m3) in g  - 1650 gm ( Constant for each test)
5. Mass of sand in the hole (mb) = (m1- (m2+m3)  in g = 8000 - (2940+1650) = 3410gm
6. The volume of the hole  V =  mb/ρs in cm3  = 3410/1.47 = 2320gm
7.  Let us assume Mass of Wet Soil dug from the hole (mw) in gm  -  5230 gm (let us say)   

 In-Place Wet Density of Soil in g/cm3

ρm = mw / v = 5230/2320 = 2.255 g/cm3

MOISTURE CONTENT DETERMINATION (ASTM - 2216)

1. Mass of container (w1)                            = 145 gm (Let us say)
2. Mass of wet soil with the container (w2)  = 700 gm ( Let us say we kept this mass in Oven)
3. Mass of dry soil with the container (w3)   = 680 gm ( Wet soil sample shall be dried in hot oven up to 16 hours or up to next day)  
4. Mass of Moisture (M) = (  w2 - w3)        =  700 - 680 = 20gm
5. Mass of Dry soil (Md) = (w3 - w1)          =  680 - 145 = 540gm

Moisture content in percentage nearest to 1 %

ω = (M/Md) X 100 in Percentage 

ω = (20/535) X 100 =  4 %

In place dry density of soil (ρw) nearest to .01 %

(ρd) = [100 ρm / (100+ω)]

(ρd) = [(100X2.255) / (100+4)

(ρd) = 2.17 g/cm3

Relative compaction in %

                   Maximum Dry Density  ρmax  (in g/cm3)      =   2.444  gm/cm3
                 Optimum Moisture content in %                  =  4%

                 In place, dry unit weight  Kn/m3    =  (ρd X 9.807) =  (2.17X 9.807) = 21.28 Kn/m3

                    Relative Compaction  =  (ρd/ρmax)X100 = 89%

In most of the projects required compaction is 95% to 98%. It is a must to achieve the value more than the project requirement. And for moisture content ± 2 or 3 % of optimum moisture content percent is permitted.

NOTE: - NEXT LAYER SHALL NOT BE COMPACTED OR SPREAD ON TESTED LAYER TILL RESULTS ARE NOT FOUND SATISFACTORY ON REPORT WITHOUT RESULT LAYING OF NEXT LAYER IS CONSIDERED NON CONFORMITY. 

                                                                                                         

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