Atterberg's Limits Faculty of Applied Engineering and Urban Planning Civil Engineering Department Soil Mechanics ECGD3303 Atterberg's Limits Lecture 4 Week 2 1st Quadester 2007/2008 UP Copyrights 2007
Content Soil Consistency Atterberg Limits Plasticity Index Liquid Limit Plastic Limit Shrinkage Limit Plasticity Index Liquidity Index Plasticity Chart
Soil Properties Engineering Properties Index properties Shear strength – stability of slopes, B.C of soil & earth pressure on retaining wall Permeability - seepage through earth masses Compressibility - settlement Index properties The properties of soils which are not of primary interest to the geotechnical engineer but which are indicative of the engineering properties are called index properties Soil classification
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: Solid Semi-Solid Plastic Liquid - Shrinkage Limit (SL) LI = 0 Moisture Content (w) Plastic Limit (PL) Liquidity Index (LI) Plasticity Index (PI) = PL - LL Liquid Limit (LL) 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/m2)
Liquid Limit - Measurement First Method Casagrande Apparatus ASTM D-4318
Liquid Limit - Measurement Liquid Limit (LL) at N = 25
Liquid Limit – Flow Index
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
Question!! Plasticity Index - Definition PI (%) = 4.12 IF (%) PI (%) = 0.74 IFC (%) 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: Solid Semi-Solid Plastic Liquid - Shrinkage Limit (SL) LI = 0 Moisture Content (w) Plastic Limit (PL) Liquidity Index (LI) Plasticity Index (PI) = PL - LL Liquid Limit (LL) 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