Prepared By Group #4Abdul Majid,Syed Izaz Ur Rahim,Ansar Ullah,Taimur Khan,Aimal Khan,Mohammad Shoaib
Before starting of Hydrometer Analysis, we should know the whole procedure and Calculation of Sieve Analysis. So here is a Outline for Sieve Analysis.
Sieve AnalysisSieve Analysis is used for Grain Size Distribution(GSD) for grains larger than 0.075mm(75 micro m).The grains that passed through sieve #200(>0.075mm) , so its size will must less than 0.075mm and greater than 0.5micro m.Sieve analysis distribute Coarse, Fine and medium sizes But in Hydrometer analysis Silt, Clay, and Finer grains can be distributed.It is necessary that the preparation of both two test done at a time.(If possible)
Hydrometer method is used to determine the distribution of the finer particles. Standard Reference: ASTM D 422 - StandardTestMethod for Particle-SizeAnalysisof Soils.
Generally in Sieve analysis the soil that passes through sieve #200, that soil used for Sedimentation (Hydrometer Test).
Hydrometer Test is based on Stokes Law
ContHydrometer analysis is based on the principle of sedimentation of soil grains in water.
When a soil specimen is dispersed in water , the particles settle at different velocities, depending on their shape, size, weight, and viscosity of water.
Purpose: Hydrometer test is the process by which fine-grained , clay ,and Silts are graded.
This test is performed if the grain sizes are too small for Sieve analysis. Hydrometer Analysis
This test used for 0.075mm>D>0.5m of particles.Procedure: Take a sample of Soil which passed through Sieve #200.In Sieve Analysis
Weight soil Sample(that passed through sieve #200) and add with distilled water to prepare a solution.Add 125mL of dispersion agent like Sodium Hexa-meta-phosphate. Procedure
ProcedureTransfer the soil slurry into a mixer by adding more distilled water, if necessary, until mixing cup is at least half full. Then mix the solution for a period of two minutes. Immediately transfer the soil slurry into the empty sedimentation cylinder. Add distilled water up to the mark. Cover the open end of the cylinder with a stopper and secure it with the palm of your hand. Then turn the cylinder upside down and back upright for a period of one minute. (The cylinder should be inverted approximately 30 times during the minute.)
ProcedureSet the cylinder down and record the time. Remove the stopper from the cylinder. After an elapsed time of one minute and forty seconds, very slowly and carefully insert the hydrometer for the first reading. (Note: It should take about ten seconds to insert or remove the hydrometer to minimize any disturbance, and the release of the Engineering Properties of Soils Based on Laboratory Testing hydrometer should be made as close to the reading depth as possible to avoid excessive bobbing).
Take hydrometer readings after elapsed time of 2 and 5, 8, 15, 30, 60 minutes and 24 hours
When a Hydrometer placed in the soil suspension at a time t measure from the start of sedimentation it measures the specific gravity in the vicinity of its bulb at a depth L.
The larger Particles would have settled beyond the zone of measurement.
Note that L is the depth measure from the surface of the water to the center of gravity of the hydrometer bulb at which the density of the suspension is measured. The value of L is change with time t.
Why L is changing?
The lower the density of the substance, the farther the hydrometer will sink. That's why L is changing.Now L is known , t is known, the Diameter D is unknown, which can be find from the following equations
Hydrometer Readingl(cm)016.3116.1216315.8415.6515.5615.3715.2815914.8L=L1+1/2(L2-Vb/A)L2=length of the hydrometer bulb=14cmVb= vol. of the hydrometer bulb=67cu.mA=cross sectional area of the sedimentation cylinder=27.8sq.cmL1=10.5cmL=16.29-0.164R
Comparison B/W Sieve and Hydrometer Analysis