Faculty of Applied Engineering and Urban Planning Civil Engineering Department Soil Mechanics ECGD3303 Atterberg's Limits Lecture 4 Week 2 1 st Quadester 2007/2008 UP Copyrights 2007
Content Soil Consistency Atterberg Limits Liquid Limit Plastic Limit Shrinkage Limit Plasticity Index Liquidity Index Plasticity Chart
Soil Consistency Soil consistence provides a means of describing the degree and kind of cohesion and adhesion between the soil particles as related to the resistance of the soil to deform or rupture Soil Behave Like: SOILD at very low moisture content LIQUID at very high moisture content
Soil Consistency - Atterberg Limits Depending on Moisture Content soil can be divided into: 1.Solid 2.Semi-Solid 3.Plastic 4.Liquid Shrinkage Limit (SL) Plastic Limit (PL) Liquid Limit (LL) Plasticity Index (PI) = PL - LL Moisture Content (w) + - Liquidity Index (LI) LI = 0 LI = 1
Questions?! 20:00 min
Liquid Limit - Definition Liquid Limit (LL) is defined as the moisture content at which soil begins to behave as a liquid material and begins to flow (Liquid limit of a fine-grained soil gives the moisture content at which the shear strength of the soil is approximately 2.5kN/m 2 )
Liquid Limit - Measurement First Method Casagrande Apparatus ASTM D-4318
Liquid Limit - Measurement Liquid Limit (LL) at N = 25
Liquid Limit – Flow Index Flow Index N 2 =30N 1 =20 w 1 =44 w 2 =39
Liquid Limit - Measurement Second Method Fall Cone Method BS1377
Liquid Limit - Measurement Liquid Limit (LL) at d = 20 mm
Questions?! 45:00 min
Plastic Limit - Definition The moisture content (%) at which the soil when rolled into threads of 3.2mm (1/8 in) in diameter, will crumble.
Plastic Limit - Measurement First Method ASTM D-4318 PL = w% at d 3.2 mm (1/8 in.)
Plastic Limit - Measurement Second Method Fall Cone Method BS1377 Plastic Limit (PL) at d = 20 mm
Questions?! 75:00 min
Plasticity Index - Definition Plasticity Index is the difference between the liquid limit and plastic limit of a soil. PI = LL – PL
Plasticity Index - Definition PI (%) = 4.12 I F (%) PI (%) = 0.74 I FC (%) Question!! Which PI is more reasonable for construction projects? The high one or the low one?!
Questions?! 90:00 min
Shrinkage Limit - Definition The moisture content, in percent, at which the volume of the soil mass ceases to change
Shrinkage Limit - Definition
Shrinkage Limit - Measurement
Questions?! 90:00 min
Soil Consistency - Atterberg Limits Depending on Moisture Content soil can be divided into: 1.Solid 2.Semi-Solid 3.Plastic 4.Liquid Shrinkage Limit (SL) Plastic Limit (PL) Liquid Limit (LL) Plasticity Index (PI) = PL - LL Moisture Content (w) + - Liquidity Index (LI) LI = 0 LI = 1
Liquidity Index - Definition
Plasticity Chart - Definition Casagrande (1932) studied the relationship of the plasticity index to the liquid limit of a wide variety of natural soils. He proposed a plasticity chart
Organic Inorganic Silt Clay
Questions?! 120:00 min