lab report soil sand replacement method.docx

TITLE: FIELD DENSITY OF SOIL Introduction The dry density of the compacted soil or pavement material is a common measure of the amount of the compaction achieved during the construction. Knowing the field density and field moisture content, the dry density is calculated. Therefore field density test is importance as a field control test for the compaction of soil or any other pavement layer. Determination of field density of cohesion less soil is not possible by core cutter method because it is not possible to obtain a core sample. In such situation, the sand replacement method is employed to determine the unit weight. In sand replacement method, a small cylindrical pit is excavated and the weight of the soil excavated from the pit is measured. Sand whose density is known is filled into the pit. By measuring the weight of sand required to fill the pit and knowing its density the volume of pit is calculated. Knowing the weight of soil excavated from the pit and the volume of pit, the density of soil is calculated. Therefore, in this experiment there are two stages: 1. Calibration of sand density 2. Measurement of soil density

Objective To determine the field density of soil by sand replacement method.

Theoretical Background A hole of specified dimensions is excavated in the ground. The mass of the excavated soil is determined. The volume of the hole is determined by filling it with clean, uniform sand whose dry density ( ρd ) is determined separately by calibration. The volume of the hole is equal to the ass of the sand filled in the hole divided by its dry density. The dry density of the excavated soil is determined as: ρ 1+w ρ¿

d=¿

Where, ρ = Density of the excavated soil W = Water content

Apparatus

1. Sand pouring cylinder 2. Calibrating container 3. Metal tray with a central hole 4. Dry sand (passing through 600μm sieve) 6. Balance 7. Scoop 8. Chisel and hammer 9. Oven 10. Big tray and small tray

Procedure Stage 1: Calibration of Sand Density 1. The volume of the calibrating container was determined from the measured dimensions of the container. 2. The sand pouring cylinder was filled with sand within 10mm of its top. The mass of the

cylinder have been determined ( M 1 ).

3. The sand pouring cylinder was placed vertically on the calibrating container. The shutter opened to allow the sand run out from the cylinder. The shutter closed when there is no further movement of the sand in the cylinder.

4. The sand pouring cylinder was lifted from the calibrating container and have been weighed ( M 3 ).

5. Again, the sand pouring cylinder was filled with sand within 10mm of its top. 6. The sand pouring cylinder was placed over a place surface, such the big tray. The shutter opened. The sand filled the cone of the cylinder. The shutter closed when no further movement of sand takes place. 7. The sand pouring cylinder removed. The sand left on the big tray collected. The mass of sand ( M 2 ¿ that had filled the cone was determined by weighing the collected sand. 8. The dry density of sand was determined.

Stage 2: Measurement of Soil Density 1. An area of about 450mm square on the surface of the soil mass was exposed. The surface down to a level surface using a chisel and hammer was trimmed. 2. The metal tray with a hole was placed on the level surface. 3. The soil though the central hole of the tray was excavated by using the hole in the tray. The depth of the excavated hole should be about 150mm. 4. All the excavated soil in a metal container was collected and the mass of the soil ( M w ) was determined. The excavated soil was placed into the oven for 24 hours to determine the water content.

5. The metal tray was removed from the excavated hole. 6. The sand pouring cylinder was filled within 10mm of its top. The mass of the cylinder ( M 4 ¿ was determined. 7. The sand pouring cylinder was placed over the excavated hole. The sand allowed to run out the cylinder by opening the shutter. The shutter closed when the hole is completely filled and no further movement of sand is observed. 8. The sand pouring cylinder was removed from the filled hole. The mass of the cylinder (

M 5 ) was determined. 9. A representative sample of the excavated soil was took. Water content and dry density were determined.

Result & Analysis Stage 1: Calibration of Sand Density 3 2 Volume of calibrating container ( m ), V= ∏ r h

−3 1.178 x 10

Mass of cylinder + cap (kg) Mass of cylinder + sand + cap (Before pouring), Mass of cylinder + sand + cap (After pouring),

5.475 9.510

M 1 (kg) M 3 (kg)

7.655

Mass of big tray (kg) Mass of big tray + sand (kg) Mass of sand, M 2 (kg)

Bulk density of the sand = ρa

=

Ma =¿ V

1.135 1.565 0.430

weight of sand filled∈the calibrating container volume of thecalibrating container

( M 1−M 3−M 2) V

=

(9.510−7.655−0.430) 1.178 x 10−3

3 = 1209.68kg/ m

Stage 2: Measurement of Soil Density Volume of calibrating container ( m

3

), V= ∏ r

2

h

Mass of cylinder + cap (kg) Mass of cylinder + sand + cap (Before pouring), Mass of cylinder + sand + cap (After pouring),

−3

1.178 x 10

M 4 (kg) M 5 (kg)

5.475 9.460 7.840

Mass of small tray (kg) Mass of small tray + excavated soil (before heating) (kg) Mass of excavated soil, M w (kg)

0.245 1.875 1.630

Mass of small tray + excavated soil (after heating) (kg) Mass of sand, M 2 (kg)

1.600 0.430

Bulk density of the soil =

weight of the excavated soil x bulk density of sand weight of sand ∈the hole

ρb

=

Mw x ρa = Mb

Mw xρ ( M 4−M 5 −M 2) a =

1.630 x (9.460−7.840−0.430) 1209.68kg/

m3 3 =1656.96kg/ m

Dry density of the soil Moisture content =

1.875 – 1.630 x 100% = 14.67% 1.875

Dry density of soil,

ρd =¿

ρd =

1656.96 1+ 0.131

Density of excavated soil 1+ Water content

ρ

= 1+ w

3 =1465.04 kg/ m

Discussions The objective of sand replacement test is to determine the field density of natural using sand pouring cylinders. The relationship between the dry density with known moisture content is ρ 1+w ρ¿

d=¿

d=¿ ρ¿ Dry density ρ = Density of the excavated soil W = Moisture content Dry density,

ρd

is a dry density of the soil, density of the excavated soil, ρ is a bulk

density of the soil that we get from measurement of soil density and moisture content, W is a percent of the water content from sample that we heated for 24 hours in the oven. If the amount of moisture content is lowest, the amount of dry density is highest. There are several error in this experiment that we must to correct. In stage 2, which is measurement of soil density, make sure the excavated hole must be equal to the volume of the calibrating container. While calibrating the bulk density of sand, make sure great care has to be taken. The apparatus that we need in this test are sand pouring cylinder, tools for excavating holes, cylindrical calibrating container, metal tray and weighing balance. The different method for

the determination of field density of soils instead of sand replacement method such as core cutter method which is suitable for cohesive soil, rubber balloon method which is like as sand replacement method but it use water in this experiment and nuclear gauge method which is the easier way to measure both bulk and water content of in situ soil.

Conclusion What we can conclude from the test is sand replacement is to determine the field density of soils using sand replacement method. From the experiment, we have found that moisture 3 content is 13.1% and our dry density of soil is 1465.04kg/ m .

CONTENT

Experiment 1 – Particle Size Distribution (8/2/2017)

Experiment 2 – Compaction Test (15/2/2017) Experiment 3 – Sand Replacement Test (22/2/2017)