HOW TO DETERMINE RELATIVE DENSITY OF SAND?

Purpose:

This laboratory is performed to determine the relative density of cohesive, free-draining soils using a vibrating table. is the relative density ratio of a soil, expressed as a percentage, of the difference between the maximum index void ratio and the area void ratio of a cohesive, free-draining soil; To differentiate between its maximum and minimum index zero ratio.


Standard Reference:

ASTM D 4254 Standard test methods for calculation of minimum index density and unit weight and relative density of soil.

ASTM D 4253 Standard test methods for maximum index density and unit weight of soil using a vibratory table.

Importance:

Relative density and percentage compaction are commonly used to evaluate the concentration status of a given soil mass. The engineering properties of a given soil, such as shear strength, compressibility and permeability, depend on the level of compaction.

Device:

  • vibrating table
  • Mold assembly (consisting of standard mold, guide sleeves, surcharge base-plate, surcharge weight, surcharge base-plate handle and dial-indicator gauge)
  • balance
  • Scoop
  • straight edge

Testing Process:

(1) Fill the mold with soil (about 0.5 inch to 1 inch above the top of the mold) using a scoop or pouring tool (funnel) by pouring the soil as loosely as possible. The spiral motion should be sufficient to minimize particle separation.

(2) Trim off excess soil level from above by carefully trimming the surface of the soil with a straightedge.

(3) Determine and record the mass of mold and clay. Then empty the mold (M1) see fig-1.

Figure-1 (Relative Density Testing Equipment)
Figure-1 (Relative Density Testing Equipment)

(4) Fill the mold again with soil (do not use the clay used in Step 1) and level the surface of the soil using a scoop or pouring tool (funnel) to minimize soil separation. The sides of the mold can be struck several times using a metal bar or rubber hammer to settle the mold so that the overload base-plate can be easily positioned and no buoyancy of air out of the mold when vibration is initiated. Don’t be

(5) Place the surcharge base plate on the soil surface and fold it a few times so that it is firmly and uniformly in contact with the soil surface. Remove the surcharge base-plate handle.

(6) Attach the mold to the vibrating table.

(7) Determine the initial dial reading by inserting a dial indicator gauge holder into each guide bracket with the dial gauge stem in contact with the rim of the mold (at its center) on both sides of the guide bracket. get six sets Dial indicator readings, three on each side of each guide bracket. The average of these twelve readings is the initial dial gauge reading, RI, Record Re to the nearest 0.001 inch (0.025 mm). See fig-2.

(8) Attach the guide sleeve to the mold firmly and reduce the appropriate overload load on the overload base-plate. See fig-2.

Figure-2 Relative Density Test of Sand
Figure-2 Relative Density Test of Sand

(9) Vibrate the mold assembly and the soil sample for 8 min.

(10) Determine and record the dial indicator gauge reading as in step (7). The average of these readings is the final dial gauge reading, RF,

(11) Remove the surcharge base-plate from the mold and detach the mold from the vibrating table.

(12) Determine and record the mass of mold and clay (M2,

(13) Empty the mold and set the weight of the mold.

(14) Determine and record the dimensions of the mold (ie diameter and height) to calculate the calibrated volume of the mold, vC, Also, set the thickness of the overload base-plate, TeaP,

Analysis:

(1) Calculate the minimum index density (Ioppressed) as follows:

Ioppressed , MS1/vC

Where

MS1= Mass of the test-dry clay = Mass of the mold with loose soil – Mass of the mold

vC= calibrated quantity of mold

(2) Calculate the maximum index density (Idmax) as follows:


Idmax = mS2/v

Where

MS2 = mass of test-dry clay = mass of mold with clay after vibration – mass of mold

v = Volume of test-dry soil = vC – (aC*h)

Where

aC = calibrated cross sectional area of ​​the mold

h = [Rf –Ri] +TP

(3) thus calculate (use) the max- and min-index zero ratio Yess The value determined from the specific gravity test; Iwoo = 1 g/cm3,

IMinute , [(ρw*Gs / ρdmax) – 1]

IMax , [(ρw*Gs / ρdmin) – 1]


(4) Calculate the relative density as follows:

DD , [(emax – e) / (emax – emin)]

To calculate the zero ratio (I) of the natural state of the soil, first calculate the density of the soil (ID) And Is=gs,Iwoo (Use Yess The value determined from the specific gravity test) is as follows:

I ,IsD)-1

article written by

Pro. Krishna Reddy, UIC]

Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at ProCivilEngineer.com Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.