Hydraulic Structures: Fourth Edition

InstabilityFoundation slip

Surface displacement of

Soft or weak founda-

Consolidate soil; drainage;

ground near toe of slope

tion and/or high pore-

ground improvement

water pressures

Face slopes

Change in morphology;

High porewater

Drainage; flatten slope or

bulging and deformation,

pressure; slopes

construct stabilizing berms

leading to rotational or

too steep; rapid draw-

translational slip

down on upstream slope

Flowslide

Sudden liquefaction,

Triggered by shock

Adequate compaction/

rapid flow mechanism

or movement; silty

consolidation or toe berm added

soils at risk

DeformationSettlement

Loss of freeboard;

Deformation and consolida-

Restoration of freeboard; good

local low spots

tion of dam and/or

internal detailing to reduce risk

foundation; result of

of cracking, e.g. protective filters

internal erosion etc.

Internal

External profile deforma-

Relative deformation

Good detailing, with wide

tion; internal cracking

of zones or materials

transition zones etc.