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

Seepage in Soil

Laplace’s equation

Laplace’s equation

Laplace’s equation

Darcy’s law:

Laplace’s equation

If the permeability of soil is isotropic (kx=kz):

Pierre-Simon Laplace (1749-1827)

Laplace’s equation

Solution for simple 1D flow problem

Solution for simple 1D flow problem

Flow nets

Flow nets

Flow nets

Equipotential lines intersect flow lines at right angle. The intersections form approximately squares

Seepage calculation from flow nets

Example

Flow nets in anisotropic soil

Flow nets in anisotropic soil

Example

Example

Uplift pressure under hydraulic structures

Uplift pressures at a, b, and f = ?

Seepage through earth dam on impervious layer

∆=𝐻

tan𝛽

Filter design

Filter design

Terzaghi – Peck Filtration Criterion

Filter design