FLATGEO Consulting Co., Ltd.

List of Standards

List of Standards

The list of standards (ASTM, BS and TCVN) which are commonly used in...

Holiday calendar in 2019

Holiday calendar in 2019

Date Number of days off 2019  New Year's...

Standard Penetration Test

Standard Penetration Test

Standard penetration test (SPT) is one of the most common in situ testing...

Precision or Accuracy ???

Precision or Accuracy ???

When working with technical documents, readers are often deal with specific...

Bulk Density

Bulk Density

1. Definition: A bulk density of a soil sample is defined as a mass per...

Compaction Test

Compaction Test

1. Definition: The bulk density or dry density of soils is not a constant...

Warning on Webpage Content Stealing

Warning on Webpage Content Stealing

On February 27, 2014, flatGEO Consulting Co. accessed to a webpage on...

Datalogger for Oedometers

Datalogger for Oedometers

After a four-month-trial period, flatGEO has finished a datalogger system for...

  • List of Standards

    List of Standards

    July 18, 2011
  • Holiday calendar in 2019

    Holiday calendar in 2019

    October 2, 2011
  • Standard Penetration Test

    Standard Penetration Test

    December 12, 2011
  • Precision or Accuracy ???

    Precision or Accuracy ???

    January 7, 2012
  • Bulk Density

    Bulk Density

    February 20, 2012
  • Compaction Test

    Compaction Test

    March 7, 2012
  • Warning on Webpage Content Stealing

    Warning on Webpage Content Stealing

    February 27, 2014
  • Datalogger for Oedometers

    Datalogger for Oedometers

    July 21, 2015
09788305
Today
This week
This month
1859
5163
31624
Your IP: 3.214.224.224

Albert Mauritz Atterberg1. Atterberg limits:

A soil sample will expose its consitency when it is composed of some clay and silt fractions and has some moisture content. The consistency of a soil sample will change in relation to the changing of moisture content. This relationship is presented by Albert Mauritz Atterberg in the following figure:

 

Atterberg limits (Source: C. Venkatramaiah, Geotechnical Engineering)

Based on that concept, Atterberg introduces three limit values (so-called Atterberg limits): liquid limit, plastic limit, shrinkage limit.

  • Liquid limit LL is the moisture content at which a soil sample changes from the plastic phase to the liquid phase. In the plastic phase, the volume of the soil sample will decrease linearly with decreasing of moisture content.
  • Plastic limit PL is the moisture content at which a soil sample changes from the plastic phase to semi-solid phase. In the semi-solid phase, the volume of the soil sample will decrease curvilinearly with the decreasing of moisture content.
  • Shrinkage limit SL is the moisture content at which the soil sample changes from the semi-solid phase to the solid phase. In the solid phase, the volume of soil sample will not change even though its moisture content decreases.

2. Liquidity index of a soil sample:

The consistency of a soil sample is expressed by the parameter "liquidity index", denoted by LI. The liquidity index is calculated by scaling the natural moisture content to the liquid limit and plastic limit by the following formula:

liquidity

However this comparison is illogical because of some reasons as follows:

  • The moisture content of a soil sample is carried out on the whole sample including both a coarse portion (considered as a non-plastic component) and a fine portion (considered as a plastic component).
  • The liquid limit and plastic limit are carried out on the fine portion only. The boundary between a coarse portion and a fine portion is dependent on applied standards. For instance, this boundary is 1.0 mm for Vietnamese standard and 0.425 mm for ASTM or BS.

3. Corrected liquidity index:

In order to have a more logical liquidity index, researchers introduces a method of correction for the liquidity index: either the moisture content will be corrected to the equivalent moisture content of a fine portion; or the liquid limit and plastic limit will be corrected to the equivalent limits for the whole sample.

Applied standard Method of correction Range of correction
Vietnamese standard
TCVN 4197:1995
Liquid limit and plastic limit are corrected to their equivalent limits for the whole sample.

The corrected liquidity index is calculated by following formula:

liquidity norm

where:

w is the natural moisture content of a soil sample

PL* and LL* are corrected values of plastic limit and liquid limit, using the following formula:

plastic norm

liquid norm

Pa is the cumulative percentage of particles passing 1.0 mm

The correction is applied only for samples whose coarse portion (> 1.0 mm) is from 10 % to 50 %
British standard
BS 1377:1990
The natural moisture content w of a soil sample is corrected to the equivalent moisture content wa of a fine portion only.

moisture norm

(Pa is the cumulative percentage of particles passing 0.425 mm)

Then the liquidity index is calculated by following formula:

liquid norm2

The correction is applied for all samples
American standard
ASTM D4318
no correction required -

Meanwhile BS 1377 requires to make the correction for every samples regardless its amount of coarse portion but Vietnamese standard TCVN 4197 only applies the correction for samples whose coarse portion are between 10 % and 50 %.

How does TCVN 4197 find out the limit values of 10 % and 50 % ?Are these limit values logical ? These questions have no answers so far

Add comment

Security code
Refresh