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