Lab reports on determination of field density of soil mass by sand replacement method

 

TITLE: DETERMINATION OF FIELD DENSITY OF SOIL BY SAND REPLACEMENT METHOD

OBJECTIVES:

• To determine the field density of soil mass by sand replacement method 

APPARATUS REQUIRED:

•            Sand – pouring cylinder

•            Calibrating container, 100mm diameter and 150mm

•            Soil cutting and excavating tools

•            Plane surface: Glass or Other Plane Surface

•            Metal container to collect excavated soil

•            Metal tray, 300mm square and 40mm deep

with a hole of 100mm in diameter at the center

•            Weighing balance accurate to 1 gram

•            Moisture content cans

•            Oven

MATERIALS REQUIRED:

•      Clean, uniform sand passing 1mm IS sieve and retained on 600 micron IS sieve in sufficient quantity. It is required to be free from organic substances. The sand should have been dried in an oven and kept in suitable storage for a period of time to allow its water content to reach equilibrium with atmospheric humidity.

THEORY:

•            The in  situ dry density of soil. The procedures, materials, equipment, and specifications of this test is based on the Indian Standard (IS 2720 part 28). This test is of significant importance and it has been widely used in various construction project sites.

•            The sand replacement test method is also used to determine the in-place density of compacted soil in order to compare it with the designated compaction degree, hence it specifies how much the compaction of the soil is close to the designated compaction degree.

Calibrations

              1.First of all, Measure the internal dimensions of the calibrating container and then calculate its volume.

 Fil2.the sand-pouring cylinder with sand, within about 10mm of its top. Determine the weight of the filled cylinder (M₁).

•            3.Place the sand-pouring cylinder vertically on the calibrating container. Open the shutter to allow the sand run out from the cylinder. When there is no further movement of the sand in the cylinder, close the shutter.

•            4.Lift the pouring cylinder from the calibrating container and weigh it to the nearest gram (M2).

•            5.Place the sand pouring cylinder on the glass plate. Open the shutter and allow the sand to run out of the cylinder until no further movement of the sand is noticed (sand fills the cone of the cylinder), and then close the shutter and remove the sand pouring cylinder carefully.

•            6.Take the sand on the glass plate and determine its weight (M₃)

•            7.Repeat step 3 to step 6 two more times and record mean weight (mean M₂ and M3)

•            8.  Determine the dry density of sand, as shown below.

bb    CALIBRATION FOR DRY DENSITY OF SAND:

1.        Diameter,D=100 mm
2.       height of container,H=150mm
3.      Volume of container,V=pi/4*d^2*H=1178.097 cc
4.       Mass of pouring cylinder filled with sand (M1)=6761 gm
5.       Mass of pouring cylinder after pouring sand into the calibrating container and cone (M2)=4790 gm
6.       Mass of sand in the cone (M3)=325 gm 

      Calculation:

          mass of sand in calibrating container,Mc=M1-M2-M3=6761-4790-325=1646 gm

          Dry density of sand,p =Mc/V=1646/1178.097 =1.397 gm/cc

 

        FIELD PROCEDURE:

  1.    1.Expose an area of about 450mm square on the surface of the soil mass. Trim the surface down to a level surface using a scrapper tool.

•              2.Place the metal tray on the leveled surface.

•            3.  Excavate the soil though the central hole of the tray, using the hole in the tray as a pattern. The depth of the excavated hole should be about 150mm.

•                4. Collect all the excavated soil in a metal container, and determine the mass of the soil (M).

•                5.Remove the metal tray from the excavated hole.

•               6.Fill the sand pouring cylinder within 10mm of its top. Determine its mass (M₁).

•                7.Place the cylinder directly over the excavated hole. Allow the sand to run out the cylinder by opening the shutter. Close the shutter when the hole is completely filled and no further movement of sand is observed.

•              8. Remove the cylinder from the filled hole. Determine the mass of the cylinder (M₄).

•              9.Take a representative sample of the excavated soil. Determine its water content.

•              10.Determine the dry density of soil as shown in Table 2.

        OBSERVATION AND CALCULATION FOR FIELD DENSITY:

1.             Mass of excavated soil , M=1457-18 =1439 gm
2.           Mass of pouring cylinder, filled with sand,(M1)=6761 gm
3.          Mass of cylinder after pouring into the hole and cone,(M4)=5045 gm

CALCULATIONS:

       Mass of sand in the hole,Ms=M1-M4-M3=6761-5045-325=1391 gm

       Volume of sand in the hole,V=Ms/Ps=1391/1.397=995.705 cc

        Bulk density p=M/v=1439/995.705=1.445 gm/cc

        Water content,w=17 %

         Dry density,Pd= P/(1+w)=1.235 gm/cc

       

       RESULT:

       From above field procedure and calibration test , we have found:

        Density of sand, Ps=1.397 gm/cc

         Field Density of soil, P=1.445 gm/cc

        Dry density of soil,Pd=1.235 gm/cc

CONCLUSIONS:

Hence , by this way, we can calculate the field density of soil in field. The field density may vary place to place dedending upon th soil composition, natural water content,ground condition etc. This method can use for cohesive as well as non-cohesive soil.

PRECAUTIONS:

1. All the measurement should measure accurately.
2. The shutter should close toghtly after pouring of sand to prevent spill out.
3. The depth of excavation should nearly equal to 10 cm dia and about 15 cm depth for precise data measerement.
4. Excavated soil should collect without spilling over pan.