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List of Standards

List of Standards

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

Holiday calendar in 2023

Holiday calendar in 2023

Date Number of days off 2023  New Year's...

Upcoming Events

Upcoming Events

Upcoming events Date Location The 21st Southeast Asian...

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...

  • List of Standards

    List of Standards

    July 18, 2011
  • Holiday calendar in 2023

    Holiday calendar in 2023

    October 2, 2011
  • Upcoming Events

    Upcoming Events

    December 3, 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

Slide01 liquid limitA liquid limit is one of important physical properties of a soil sample for soil classification. In principle, Atterberg limits (including liquid limit, plastic limit, shrinkage limit) must be unique and typical for each soil sample. However, in practical, the liquid limit is not unique at all and varies with the testing equipment, testing method and even the emotions of operators (!)

In theory, the liquid limit is the moisture content at which the soil sample changes from plastic state to liquid state. But how to determine properly this boundary between plastic and liquid states?

Nobody knows how Mr. Arthur Casagrande derived his device for liquid limit determination but this device was published in 1931 and is used commonly nowadays. Casagrande’s device operates on the ‘dynamic’ principle: a soil cup impacts on a rubber base to obtain a necessary action.

Casagrande_apparatus     Casagrande_soil_pat
Casagrande's device   Soil pat before testing

 

Therefore, the liquid limit based on this device will depend on the drop height of a soil cup, the hardness of a rubber base. According to ASTM standard, the rubber base has a Type D Durometer hardness of 80~90, meanwhile the rubber base of BSI standard has a IRHD hardness of 84°~94° which is equivalent to the Type D Durometer hardness of 30~40. Consequently, which value is the real liquid limit of a soil sample?

Even worse, the researchers introduce another device for liquid limit determination based on the “static” principle: a penetrometer. The penetrometer of predefined mass will drop freely into a soil cup. The liquid limit will determine when its penetration reachs the predefined depth. The values of liquid limit based on the penetrometer will vary with the mass of penetrometer, apex angle and predefined depth. And consequently, the liquid limits obtained from penetrometers vary largely with different penetrometers.

Following table presents some of penetrometer types used in different countries.

  Apex angle Mass of penetrometer Predefined depth at the liquid limit
England, New Zealand 30° 80 g 20 mm
Russia, Vietnam 30° 76 g 10 mm
Trung Quốc 30° 76 g 17 mm
India 30° 148 g 25.4 mm
Canada, Sweden, Norway 60° 60 g 10 mm
Japan 60° 60 g 11.5 mm

 

cone_1     cone_2
Dial gauge cone penetrometer   Electronic cone penetrometer

 

Once again, the engineers and technicians are facing up the problem “which value is the real liquid limit of a soil sample?” Perhaps soil engineers should ask Mr. Arthur Casagrande for help. Waiting for his answer, geotechnicans should make clearly whenever dealing with the liquid limit: a) the device (Casagrande device or penetrometer); b) Relevant properties of a used device.

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