CE281-Geotechnical Engineering I
Sand Cone Test
DETERMINATION OF DRY DENSITY OF SOIL BY SAND REPLACEMENT METHOD OBJECTIVE
To determine the field density of soil at a given location by sand replacement method
INTRODUCTION Sand replacement test method is used to determine the field density or in-place density of earth embankments, road fills, sub-grade, sub-base or any of compacted material. The moisture content of the soil vary from time to time and hence the field density also, so it is required to report the test result in terms of dry density. In order to determine the dry density we must have to examine the moisture content in the soil by using general method. Commonly used methods to determine the field unit weight of the soil are; o Sand cone method o Rubber balloon method o Core cutter method o Nuclear method THEORY In this lab session, the Sand Cone Method was used to determine the dry density of soil. 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.
Figure 1: Sand replacement method Chandrasena O.
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CE281-Geotechnical Engineering I
Sand Cone Test
W 1−W 3−W 2 Va
Bulk density of sand, ρsand =
Weight of sand filling excavated hole alone, Wb = W 1−W 4−W 2
Volume of excavated soil, V =
W 1−W 4−W 2 ρ sand
In-situ bulk density of the wet excavated soil, ρs =
W5 V
100 ( W −W d ) Wd
Moisture content of soil, w% =
In-situ dry bulk density of the wet excavated soil, ρd = ρs ×
Wd V
= ρs
100 (100+w )
Notations: Ρs
= Bulk density of the soil sample
ρd
= Dry density of the soil sample
ρsand
= Bulk density of sand
W2
= Weight of sand required to fill cone
V
= Volume of excavated soil
Va
= Volume of the container
w%
= Water content of the soil sample
W1
= Weight of cylinder and sand filled up to 10mm from top edge
W3
= Weight of cylinder and sand after pouring into calibration container and cone
W4
= Weight of cylinder and sand after pouring into excavated hole and cone
W5
= Weight of soil from excavated hole
Wd
= Oven dry weight of the soil sample
W
= Weight of the wet soil sample
Chandrasena O.
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CE281-Geotechnical Engineering I
Sand Cone Test
MATERIALS AND APPARATUS 1. 2. 3. 4. 5. 6. 7. 8.
Sand pouring cylinder with fitted valve, metal funnel and base plate. Uniform fine sand with grain size ranges from 1.00mm to 0.60mm. Digging tools such as scrapper tool, bent spoon to dig a hole in the soil. Airtight container to collect the removed soil. Drying can for water content determination. Balances sensitive to 1g and 0.01g. Drying oven with temperature ranges from 105 0C to 110 0C. Desiccator.
Figure 2: Sand pouring cylinder with fitted valve, metal funnel and base plate
Figure 3: Digging tools
PROCEDURE Chandrasena O.
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CE281-Geotechnical Engineering I
Sand Cone Test
In this experiment there are two stages: o Calibration of apparatus o Measurement of field density (i)
Calibration of apparatus
1. The top cap of the cylinder was removed, the shutter was closed and the cylinder was filled with specially graded sand up to about 10mm from the top and cap was replaced. 2. The weight of the cylinder was measured with sand accurate to one gram (W1). 3. The cylinder was placed on a clean plane surface and the shutter was kept open till the sand filled up the cone fully. The shutter was closed and the sand collected on the plate (W 2) was weighed. 4. The cylinder was refilled with the sand such that it gets the initial weight (W1). 5. The cylinder was placed over the calibration container and the shutter was opened until the cone and the container volume were completely filled with sand (W3). 6. The volume of the container (Va) was determined by measuring the internal diameter and the height of the container.
(ii)
Measurement of field density
1. The ground surface was leveled off and the base plate was positioned horizontally at the location where the density was to be determined. 2. A hole was dug within the opening of the base plate; this opening size of the hole to be slightly larger than the base plate opening. It was made sure that base plate was not moved while digging the hole. It should be centered above the hole. 3. The excavated soil was stored in an airtight container and the weight (W) was measured. 4. The cylinder was refilled with sand such that it got the initial weight (W1). 5. Then the metal funnel was positioned on the groove of the base plate and the valve was opened to let the sand fill the hole. 6. The valve was closed when the sand stopped flowing and the weight of cylinder with remaining sand (W4) was measured. 7. The sand was salvaged as much as possible. 8. The water content of the soil sample was determined.
CALCULATIONS
Chandrasena O.
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CE281-Geotechnical Engineering I
Sand Cone Test
RESULTS
Bulk density of the soil,
γ = 16.92 kNm-3
Water content,
w% = 13.79%
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CE281-Geotechnical Engineering I
Dry density of the soil,
Sand Cone Test
γd = 14.87 kNm-3
DISCUSSION
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CE281-Geotechnical Engineering I
Sand Cone Test
Chandrasena O.
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CE281-Geotechnical Engineering I
Sand Cone Test
CONCLUSION
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CE281-Geotechnical Engineering I
Sand Cone Test
REFERENCES: Braja M. Das & Khaled Sobhan (2012) Principles of Geotechnical Engineering, 8th edition, United States. Determination of Dry Density by Sand Replacement Method, [Online], Available: http://civilblog.org/2014/04/02/determination-of-field-density-of-soil-by-sand-replacement-method-is2720-part-28/ [15 Aug 2015].
In-Situ Dry Density by Sand Replacement Method, [Online], Available: http://theconstructor.org/geotechnical/in-situ-dry-density-by-sand-replacement-method/2687/
[15 Aug 2015].
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