Particle Size Analysis (Sieves and Hydrometer)

Summary

In this educational video, Dave Whinger from Missouri S&T Geotechnical Labs demonstrates particle size analysis procedures essential for geotechnical engineers to classify soils. The video covers two main methods: the mechanical sieve analysis for coarse-grained soil and the hydrometer analysis for fine-grained material. These tests help characterize soil for engineering applications, such as soil description and permeability correlations. The lab uses various equipment like sieves, a mechanical shaker, and a hydrometer, and follows specific standards for accurate results. The process involves soil sample preparation, mechanical sieving, and hydrometer readings over time to determine the soil's grain size distribution.

Takeaways

• 🔬 Particle size analysis is crucial for geotechnical engineers to classify soils and ensure they are suitable for engineering applications.
• 📐 The process involves two main procedures: mechanical sieve analysis for coarse grain fraction and hydrometer analysis for fine grain fraction.
• 🏗️ Mechanical sieve analysis uses a series of sieves to determine grain size distribution, while hydrometer analysis measures the specific gravity change of a soil-water mixture over time.
• 📏 For mechanical sieve analysis, a stack of sieves with different mesh sizes (from number 4 to number 200), a pan, a lid, a mechanical shaker, a digital balance, and a weighing pull are required.
• 🧪 The hydrometer analysis requires a 1000ml sedimentation jar, a control jar, a hydrometer, a soil dispersion device, sodium hexametaphosphate, a squirt bottle with water, an evaporation dish, a rubber stopper, and a thermometer.
• 🌊 The soil sample used in the video is a silt from the Mississippi River Valley, which has been mechanically pulverized and had coarse material added for the lab.
• 📋 The lab documents, including standards and data sheets, are available on Blackboard for reference, and the particle size analysis is part of a combination lab handout.
• ⏱️ The mechanical sieve analysis involves shaking a 500g sample of air-dried soil through a series of sieves and then determining the mass retained on each sieve.
• 📊 The percentage of soil particles finer than a specific sieve size is calculated, and the results are plotted to create a particle size distribution curve.
• 🕒 The hydrometer analysis involves soaking the soil in a sodium hexametaphosphate solution, dispersing it, and then measuring the specific gravity changes at various time intervals up to 24 hours.
• 📈 The final results from both tests provide a comprehensive grain size distribution of the soil, which is essential for soil classification and engineering applications.

Q & A

What is the purpose of particle size analysis in geotechnical engineering?

Particle size analysis is used by geotechnical engineers to classify soils and determine the grain size distribution within the soil, which is essential for soil description, quantitative soil classification, and correlations to permeability based on the Hazen equation.

What are the two procedures involved in particle size analysis?

The two procedures involved in particle size analysis are the mechanical sieve analysis and the hydrometer analysis. The mechanical sieve analysis is used for the coarse grain fraction, while the hydrometer analysis is conducted on the fine grain fraction of the soil.

What materials are considered fine grain according to the script?

Material that passes the number 200 sieve is considered fine grain material.

What are the required devices for conducting a mechanical sieve analysis?

The required devices for a mechanical sieve analysis include a stack of sieves ranging from number four to number 200, a pan, a lid, a mechanical shaker, a digital balance, and a weighing pull.

What is the role of sodium hexametaphosphate in the hydrometer analysis?

Sodium hexametaphosphate is used as a soil dispersion agent to break down the cohesion between soil particles, preventing them from sticking together during the hydrometer analysis.

How long should the soil be allowed to soak in sodium hexametaphosphate solution before the hydrometer analysis?

The soil should be allowed to soak in the sodium hexametaphosphate solution for 15 minutes before proceeding with the hydrometer analysis.

What is the significance of the zero correction factor in hydrometer analysis?

The zero correction factor is used to calibrate the hydrometer by determining the distance from the zero mark to the top of the meniscus on the hydrometer staff, ensuring accurate readings during the analysis.

How is the soil sample prepared for the hydrometer analysis after the soaking period?

After the 15-minute soaking period, the soil is transferred into a dispersion cup, mixed with water, and then poured into a clean sedimentation jar. The jar is then filled to the 1000ml mark and capped with a rubber stopper.

What is the duration for which the sedimentation jar should be left undisturbed during the hydrometer analysis?

The sedimentation jar should be left undisturbed for 24 hours during the hydrometer analysis.

At what time intervals should the hydrometer and temperature readings be recorded during the sedimentation process?

The hydrometer and temperature readings should be recorded at approximate intervals of 2, 4, 8, 16, 30 minutes, and then at 1, 2, 4, 8, and 24 hours.

How is the total retained mass computed after the mechanical sieve analysis?

The total retained mass is computed by adding the individual masses retained on each sieve and the pan. The total mass should be within plus or minus 2% of the original mass.

Outlines

00:00

🧪 Introduction to Particle Size Analysis and Procedures

Dave Whinger from Missouri S&T's Geotechnical Labs introduces the laboratory procedures for conducting particle size analysis. This test is crucial for classifying soils and involves two methods: mechanical sieve analysis and hydrometer analysis. The mechanical sieve analysis determines the grain size distribution of coarse soil fractions, while the hydrometer analysis focuses on fine grains. These tests provide data used to characterize soils for engineering applications, including classification, permeability correlations, and material suitability.

05:03

🛠️ Equipment and Procedure for Mechanical Sieve Analysis

The second paragraph outlines the tools needed for the mechanical sieve analysis, including a stack of sieves (ranging from #4 to #200), a mechanical shaker, a digital balance, and a weighing bowl. It describes the step-by-step process of conducting the sieve analysis, starting with weighing 500g of air-dried soil and passing it through the sieves. The results are used to determine the particle size distribution, with a focus on the coarse-grained fraction. Attention is drawn to ensuring the total mass is within a 2% margin of error for accuracy.

10:14

📊 Performing Hydrometer Analysis and Preparing the Soil

This paragraph details the steps for conducting the hydrometer analysis, which focuses on the fine-grained portion of the soil. The procedure involves measuring 60g of the leftover soil, mixing it with sodium hexametaphosphate, and soaking the mixture for 15 minutes. This dispersion agent is crucial for breaking down the cohesion between soil particles. The paragraph also highlights the calibration of the hydrometer and introduces the concept of the zero correction and meniscus correction factors, both vital for accurate measurements during the hydrometer analysis.

⚗️ Agitating and Measuring Soil Particles Using Hydrometer

This final paragraph describes the agitating process where the soil solution is mixed and transferred into a sedimentation jar. After agitation, the hydrometer readings are taken at specific time intervals to measure the soil particles as they fall out of suspension. These readings, combined with the results from the mechanical sieve analysis, are used to calculate the complete grain size distribution of the soil sample. This comprehensive analysis gives a full understanding of the soil's characteristics.

Keywords

💡Particle Size Analysis

Particle size analysis is a method used to determine the distribution of particle sizes in a material. In the context of the video, it is a crucial procedure for geotechnical engineers to classify soils. The video demonstrates how to conduct this analysis to understand the grain size distribution within soil, which is vital for engineering applications such as soil description and permeability assessments.

💡Geotechnical Engineering

Geotechnical engineering is the branch of civil engineering concerned with the engineering behavior of earth materials. The video emphasizes its importance in utilizing particle size analysis to classify soils and make decisions on soil suitability for various engineering projects. Geotechnical engineers use the results of particle size analysis to ensure the stability and integrity of structures built on or with soil.

💡Mechanical Sieve Analysis

Mechanical sieve analysis is a procedure where a soil sample is passed through a series of sieves to determine the grain size distribution of the coarse-grained fraction of the soil. The video describes this process, which involves using a stack of sieves with different mesh sizes and a mechanical shaker to separate the soil particles. This method is part of the particle size analysis to classify the soil and is essential for understanding soil behavior.

💡Hydrometer Analysis

Hydrometer analysis is used to determine the grain size distribution of the fine-grained fraction of soil, typically the material that passes through the number 200 sieve. The video explains how this analysis is conducted by measuring the change in specific gravity of a soil-water mixture over time as particles settle out of suspension. This test is crucial for characterizing fine-grained soils and is part of the comprehensive particle size analysis.

💡Sieve

A sieve, as mentioned in the video, is a tool with a perforated surface used to separate components of a mixture by size. In the context of particle size analysis, sieves are stacked in order of increasing mesh size to separate soil particles into different size fractions. The video demonstrates the use of sieves ranging from number 4 to number 200 to determine the coarse-grained fraction of the soil.

💡Specific Gravity

Specific gravity is the ratio of the density of a substance to the density of a reference substance, usually water. In the video, the hydrometer analysis measures changes in specific gravity of a soil-water mixture over time, which is indicative of the soil particles settling out of suspension. This measurement is key to determining the particle size distribution of the fine-grained soil particles.

💡Sodium Hexametaphosphate

Sodium hexametaphosphate is a soil dispersion agent used in the hydrometer analysis to break down the cohesion between soil particles, preventing them from clumping together. The video describes its use in preparing the soil sample for analysis by soaking it in a solution of sodium hexametaphosphate, which aids in the dispersion of fine particles for accurate sizing.

💡Hazen Equation

The Hazen equation is a formula used to estimate the permeability of soil based on its grain size distribution. The video mentions that particle size analysis has practical applications in geotechnical engineering, including correlations to permeability using the Hazen equation. This equation helps engineers predict how water will flow through soil, which is important for designing structures like dams and foundations.

💡Gradation Curve

A gradation curve, also known as a particle size distribution curve, is a graphical representation of the percentage of soil particles finer than a certain size. The video explains that this curve is derived from the results of both mechanical sieve and hydrometer analyses. The gradation curve is essential for characterizing the soil and is used in soil classification and engineering applications.

💡Stokes Law

Stokes Law is a principle in fluid dynamics that describes the motion of small particles suspended in a fluid, moving towards a surface under the influence of gravity. In the video, Stokes Law is applied to determine the grain size distribution of particles falling out of suspension during the hydrometer analysis. This law helps in calculating the size of soil particles based on their settling velocity in the soil-water mixture.

Highlights

Introduction to particle size analysis procedures, focusing on its application in geotechnical engineering.

Mechanical sieve analysis is used to determine the grain size distribution within the coarse fraction of the soil.

Hydrometer analysis is conducted on fine-grained material passing through a number 200 sieve.

Practical applications include soil classification, permeability estimation, and material acceptance or rejection for engineering purposes.

A stack of sieves, a mechanical shaker, and a hydrometer are required for the test procedures.

The test sample is a silt from the Mississippi River Valley, mechanically pulverized for analysis.

The sieve analysis determines the particle size distribution curve or gradation curve for coarse soil fractions.

The procedure involves shaking a 500g sample through sieves and measuring the mass retained on each sieve.

Material passing through the number 200 sieve is considered fine-grained and is used for hydrometer analysis.

Hydrometer analysis measures changes in specific gravity over time as soil particles fall out of suspension.

Stokes' law is applied to determine the grain size distribution of particles in suspension.

The hydrometer requires calibration using a control jar filled with sodium hexametaphosphate solution.

A deviation from the ASM standard is noted: instead of 24 hours, the soil is soaked in sodium hexametaphosphate for only 15 minutes.

The gradation of fine particles is calculated based on hydrometer readings at specific time intervals (2 minutes, 4 hours, 24 hours, etc.).

Combining the mechanical sieve and hydrometer results provides a full particle size distribution of the soil sample.

Transcripts

hello I'm Dave whinger with the Missouri

S&T geotechnical Labs today we are going

to go over the laboratory procedures

used for particle size analysis this

short video will demonstrate how to

conduct particle size analysis in

accordance withm

specifications a particle size analysis

is used by geotechnical engineers to

help easily classify soils the particle

size analysis consists of two procedures

the mechanical C analysis involves the

use of a series of mechanical cves to

help determine the grain size

distribution within the coar grain

fraction of the soil the hydrometer

analysis is conducted on the fine grain

portion of the material material that

passes the number 200 Civ is considered

fine grain

material the resulting curves from these

two tests can be used to character the

soil and used to reject or accept the

material for engineering applications

the Practical applications of the

particle size analysis and geotechnical

Engineering include soil description

quantitative soil classification and

correlations to permeability based on

the Hazen equation the devices required

in order to conduct a mechanical C

analysis are a stack of

cves ranging from number four to number

200 4 10 20 40 100 200 the

pan and a

lid a mechanical

Shaker a digital

balance and a weighing

pull in order to conduct the hydrometer

analysis the following devices will be

required 1,000ml sedimentation

jar 1,000 m control

jar ANM 152h

hydrometer a soil dispersion device in

this case a shake

mixer a soil dispersion agent in this

case sodium

hexametaphosphate a squirt bottle filled

with

water an evaporation

dish a rubber stopper

and a thermometer measuring in

Celsius the soil that we will be

performing the particle size analysis

test on is a l seal silt that was

obtained from the Mississippi River

Valley the soil has been mechanically

pulverized some coarse material has been

added to the sil for the purpose of this

lab the documents pertaining to today's

lab can be found on blackboard in PDF

format the particle size analysis is

part of a combination lab handout out

entitled CE 215 lab number three and

four index tests and classification of

soils in addition ASM standards of the

two tests have been posted on blackboard

ASM c136 pertains to the Civ analysis of

fine and course grain Aggregates by the

mechanical Civ asmd 422 pertains to the

hydrometer

test also available is a data sheet for

today's lab a Civ analysis is conducted

determine the particle size distribution

curve or gradiation curve the particle

size distribution curve is a plot of the

percentage of soil particles finer

versus the log of the particle di

diameter to determine this a soil sample

is shaken through a series of cves the

mass of the soil retained on each C is

then determined from this the percentage

passing can be determined start by

weighing out a sample of 500 gr of the

provided air dry soil

start by weighing out a 500 G sample of

the provided air dried

soil it is important to mix the sample

in between each scoop so that the 500 G

sample of soil is an accurate

representation of the provided soil

sample record the total mass on the data

sheet disassemble the stack of sives

and brush out the wedged particles in

the

screens do not use the SI brush on the

number 200

Civ for this could damage the screen

with the smallest Civ on the bottom in

this case the number 200

pour the soil sample into the top of the

sives place the lid on top of the stack

of sves and with two hands carry the SIV

stack into the Shaker

room load the stack of sves into the

mechanical SIV

Shaker place the Shaker lid on top of

the stack of

lower the Shaker

hammer and turn on for 10

minutes remove the Shaker

Hammer take off the Shaker

lid and with two hands remove the stack

of sves from the Shaker and carry into

the other room

empty the material in the pan in a bowl

and record the weight this material is

the material that has passed the number

200 Civ it is considered the fine grain

portion of this material this material

will be used in the hydrometer analysis

portion of this lab compute the total

retained mass by adding the individual

masses retained on each C and the pan

the total mass should be within plus or

minus 2% of the original Mass if there

is a greater difference than this the

test must be rerun the percent passing a

specific Civ is 100 minus the summation

of all the percent retains on that Civ

and the CV's prior to

it to determine the particle size

distribution of the soil particles finer

than the number 200 Civ a hydrometer

analysis must be conducted the

hydrometer analysis measures the change

in specific gravity of a soil water

mixture over time as soil particles fall

out of suspension the specific gravity

of the soil water mixture decreases the

application of Stokes law to Falling

spheres is used to determine the grain

size distribution of the particles

falling out of suspension start the

hydrometer analysis by weighing out

exactly 60 G of the soil left over in

the pan from the mechanical C analysis

record the weight of the soil obtained

on the data

sheet in a small evaporating dish mix

the soil with 125 mL of 4% sodium

hexametaphosphate cover with a wet paper

towel and allow to stand for 15 minutes

the sodium hexametaphosphate is similar

to laundry detergent it works to break

down the cohesion between the particles

so that the individual particles will

not stick together note this is a

deviation from the ASN standard ASM

suggest that you let this sit for up to

24 hours we will only let it sit for 15

minutes in the interest of time while

the soil is soaking for 15 minutes you

can use this time to calibrate the

hydrometer each hydrometer is unique and

will have its own unique zero correction

factor to determine the zero correction

factor lower the hydrometer into a

control jar a control jar is just a

water solution with sodium

hexametaphosphate without any sort of

soil in the

water the hydrometer will eventually

stabilize the reading on the hydrometer

staff from the top of the meniscus to

the zero Mark is the zero correction

factor

also noted is the meniscus correction

factor the zero correction factor is the

distance from the zero Mark to the top

of the meniscus on the hydrometer

staff the meniscus correction factor is

the distance from the water level to the

top of the meniscus on the hydrometer

staff record the meniscus correction

factor and the zero correction factor on

your data

sheet after the 15-minute soaking

period transfer the sodium hexaphosphate

soil solution into a dispersion

cup use a squirt bottle with water to

ensure that all the material transfers

out of the evaporation

dish into the dispersion cup fill the

dispersion cup with water until the

water level is about halfway up the cup

mix with the shake mixer for 2

minutes pour the sodium

hexametaphosphate solution from the

dispersion cup into a clean

sedimentation

jar again using a squirt bottle with

water ensure that all the sediment has

transfer from the dispersion cup into

the sedimentation jar okay cap the

cylinder with the rubber

stopper agitate the solution for 1

minute by turning the cylinder upside

down and back 30 times in 1

minute after 1 minute of

agitation remove the rubber cap and use

your water squirt bottle to ensure that

all the sediment is off the cap as well

as off the sides of the sedimentation

jar fill the sediment solution up till

it is at the 1,000ml Mark place the

sedimentation jar on a table where it

will sit undisturbed for the next 24

hours after 2 minutes of placing the jar

on the table insert your hydrometer and

take the first reading at 2 minutes

record the reading on the hydrometer

staff at the top of the meniscus of the

dirty

water after the reading remove the

hydrometer place it

aside and insert the thermometer to take

a temperature

reading continue recording the

hydrometer and temperature readings at

approximate elapse times of 4 8 6 16 30

minutes 1 2 4 8 and 24 hours from the

hydrometer time history a gradiation of

the particles falling out of the

solution can be

calculated that combined with the

particle distribution curve determined

from the mechanical c will give a full

grain siiz distribution of the provided

soil