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Dear Sir ,
         what is Relation between P.L and L.L ? What is the Average value of L.L and P.L ? and i Heard from someone when L.L is large Then P.L will Low why ?


The liquid limit and plasticity limit are dependent on the clay content of the soil.

So there is not really an "average" value.  An average value can probably be derived for the different soil types, but for all soils that would be difficult.

A Plasticity chart has been derived that plots Plasticity Index of the Y axis and LL on the X.  A clay line is plotted on the chart from LL value 20 to the far right of PI of 55

The line represents the a break between silty soils below the line and clay soils above it.

The LL is the water content of the soil.  If the water content is high, then it probably contains a lot of clay.

The PL is the ability of the soil to be rolled into a fine thread of about 3.2 mm or less.  So if the LL is high, the PL will be low since the thread will not break until it is rolled down to a very fine diameter.


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Keith Patton


I can answer questions concerning physical and historical geology, environmental geology/hydrology, environmental consulting, remote sensing/aerial photo interpretation, G&G computer applications, petroleum exploration, drilling, geochemistry, geochemical and microbiological prospecting, 3D reservoir modeling, computer mapping and drilling.I am not a geophysicist.


I have 24 years experience split between the petroleum and environmental industries. I have served as an expert witness in remote sensing, developmental geologist, exploration geologist, enviromental project manager, and subject matter expert in geology and geophysical software development.

American Association of Petroleum Geologists
American Association of Photogrammetrists and Remote Sensing

Bachelor and Master of Science
Registered Geologist in State of Texas

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