Fundamentals of Geotechnical Engineering and
Laboratory Data Analysis
21-25 December 2015
Department of Civil and Environmental Engineering
Faculty of Engineering, Mahidol University
Dr. Pongpipat Anantanasakul
Plasticity and Structure of Soil
Consistency of cohesive fine-grained soils
Liquid limit (LL)
Liquid limit (LL) Before testing
After testing
Liquid limit (LL)
Liquid limit (LL) by Fall Cone Method
d: penetration of cone in 5 seconds
Liquid limit (LL) by Fall Cone Method
d: penetration of cone in 5 seconds
Plastic limit (PL)
PL is determined as the water content of soil at which it starts to crumble
When rolled into a 1/3” thread.
Plastic limit (PL) by Fall Cone Method
Typical values of LL and PL for different clay minerals
Plasticity index (PI)
PI = LL - PL
Shrinkage limit (SL)
Shrinkage limit (SL)
Liquidity index (LI) and consistency index (CI)
Skempton’s activity of cohesive fine-grained soil (A)
Plasticity chart
Soil structure
Cohesionless soil
Fabrics of granular soils
AType equation here.
• The behavior of
a granular soil is
not controlled
by the void ratio
alone.
• The fabric also
influences the
stress-strain
behavior.
𝐷𝑟 =𝑒𝑚𝑎𝑥 − 𝑒
𝑒𝑚𝑎𝑥 − 𝑒𝑚𝑖𝑛× 100%
Soil structure
Honeycomb structure of fine cohesionless soil
Soil structure
Cohesive soil
Soil structure
