Field Density Test(Sand Replacement Method)

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Field Density Test

Sand Replacement method

Objective:-

Determine the in-situ density (in g/cm3 or kg/cm3) of natural or compacted soils using sand replacement method.

Necessity of test:-

The field density of natural soil is needed for the determination of bearing capacity of soils, for the purpose of stability analysis of slopes, for the determination of pressures on underlying strata for calculation of settlement and the design of underground structures.

Apparatus:-

  1. Sand pouring cylinder of 3 lits/16.5 lit capacity.
  2. Tool for excavating holes:-scraper.
  3. Cylindrical calibrating container with an internal diameter of 100 mm/200 mm and an internal depth of 150mm/250 mm fitted with a flange 50 mm /75 mm wide an about 5mm surrounding the open end.
  4. Balance machine up to an accuracy of 1g.
  5. Glass plate about 450 mm/600 mm square and 10 mm thick.
  6. Suitable non-corrodible air-tight containers.
  7. Oven maintaining temperature between 105°C to 110°C .
  8. Natural sand passing 1mm I.S Sieve and retained on 600 micron I.S Sieve.
  9. Metal tray having hole—50mm deep and 300mm/450mm square with a 100mm/200mm diameter hole in the center.

Procedure:-

Calibration of the cylinder

  1. Fill the sand pouring cylinder with clean sand so that the level of the sand in the cylinder is within about 10 mm from the top, find out the initial weight of the cylinder plus sand (w1) and this weight should be maintained constant throughout the test for which the calibration in used.
  2. Allow the sand of volume equal to that of the calibrating container to run out of the cylinder by opening the shutter, close the shutter and place the cylinder on the glass plate. Open the shutter and allow the sand to run out . When no faster movement of sand takes place in the cylinder close the shutter and remove the cylinder carefully weigh the sand collected on the glass plate. Its weight (w2) gives the weight of sand filling the cone portion of the sand pouring cylinder.

Repeat this step at least three times and take the mean weight (w2).

Put the sand back into the sand pouring cylinder to have the same initial constant weight (w1).

Determination of bulk density of soil

  1. Determination the volume (v) of the calibrating container be filling it with water to the brim. Check this volume by calculating from the measured internal dimensions of the container.
  2. Place the sand pouring cylinder centrally on the top on the calibrating container making sure that constant weight (w1) is maintained. Open the shutter and permit the sand to run into the container. When no further movement of sand is seen close the shutter, remove the pouring cylinder and find its weight (w3).

Determination of dry density of soil In-place

  1. Approximately 60 sq cm of area of soil to be tested should be trimmed down to a level surface, approximately of the size of the container. Keep the metal tray on the level surface and excavate a circular hole of volume equal to that of the calibration container. Collect all the excavated soil in the tray and find out the weight of the excavated soil (ww). Remove the tray, and place the sand pouring cylinder filled to constant weight (w1) so that the base of the cylinder covers the hole concentrically. Open the shutter and the permit the sand to run into the hole. Close the shutter when no further movement of the sand is seen. Remove the cylinder and determine its weight (w3).
  2. Keep a representative sample of the excavated soil for water content determination.

Observations and Calculations:-

Number of Samples
S.NO.                    Sample Details                         calibration 1 2 3
1. Mean weight of sand in cone (of pouring cylinder) (w2) in gms
2. Volume of calibrating container (v) in ml
3. Weight of sand (+ cylinder) before pouring (w3) in gms
4. Mean weight of sand (+cylinder) after pouring (w3) in gms
5. Weight of sand to fill calibrating containers( wα = w1 – w3 – w2 ) in gms
6. Bulk density of sand γs = wα/v gms/cc

Number of Samples
S.NO. Measurement of Soil Density 1 2 3
1. Determination No
2. Weight of wet soil from hole (ww) in gms
3. Weight of sand (+ cylinder ) before pouring (w1) in gms
4. Weight of sand (+ cylinder ) after pouring (w4) in gms
5. Weight of sand in hole (wb = w1 – w4 – w2 ) in gms
6. Bulk densityγb= (ww/wb)× γs gms/cc
7. Water content container No.
8. Weight of soil for water content determination of gms
9. Weight of oven dried soil in gms
10. Water content ‘w’ %
11. Dry densityγd =     γb                gms/cc

1+w/100                                                                                                                                                                                                                                                                                                                                                                                                                                

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Arbaj Demrot is the founder of VideRime Online Learning, a leading engineering website. He did his BE Civil and M.Tech Structure from RGPV University, Bhopal and has been working as an Assistant Professor in a reputed college.

1 Response

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