COASTAL ENGINEERING - Introduction to Soft Soil Geotechnique: Content, Context and Application - page 265

16 COASTAL ENGINEERING

A HYDRO - GEODYNAMICS
Hydro-geodynamics in porous media refers to the mechanical response of
granular sediments when exposed to hydro-dynamic loading, i.e. water waves,
wave impacts, tides and earthquakes. Geotechnical aspects under such conditions
include: critical cross-sections and material parameters, wave/earthquake loading,
dynamic pore pressures, excess pore pressures, pore pressure build-up and
liquefaction, hydraulic (internal) filter stability, dynamic stability and residual
deformation. In this chapter these aspects are outlined to some extent.

10

8

I

6

R'

II

4

III

2

I Quarry rock, sharp, rough
II Moraine, angular, rough
III Fluvial, rounded, smooth

0

0.15 0.20 0.25 0.30 0.35 0.40 0.45

porosity n , after compaction

Figure 16.1a Equivalent roughness R'

1.0

plane test

0.8

S'/ c

0.6

0.4

triaxial test

0.2

10 100

D 50 particle size [mm]

Figure 16.1b Equivalent strength S'; c is the uniaxial rock compression strength

Rock friction
Since coastal structures usually involve coarse filter layers (stones and rock) the
corresponding internal friction angle needs some concern. Barton's formula reads

= 0 + R' log ( S'/ ' ) (16.1)