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

Origin of Soils and Grain Size

What is a soil?

Rock cycle

Rock mineralogy

Weathering of rock into soil

• Chemical weathering

• Mechanical weathering

o Temperature

o Moving water

o Glaciers

o Wind

Different soil types categorized by modes of transportation

Examples:

• Laterite soil is residual soil.

• Bangkok clay is marine soil .

• Khon Kaen loess is eolian soil.

• Ayutthaya sand is alluvial soil.

Weathering processes

Temperature: expansion, contraction Chemical

1908 1969

Wind Wave and current

Living beings: plants Living beings: humans

Weathering processes

Weathering is a process of degradation, decomposition of rock mass which results

into smaller rock (mineral) particles.

Glacier Volcanic activities

Soil-particle size

Clay minerals

Clay minerals

Clay minerals

Specific gravity

Sieve analysis

Hydrometer analysis

Particle-size distribution curve

Particle-size distribution curve

Coefficient of gradation

Uniformity coefficient

Particle-size distribution curve