Hydraulic Structures: Fourth Edition

Table 7.2 Primary monitoring parameters and their relationship to possible defectsParameter

Instruments

Measurement

Illustrative defect

Dam type

Seepage

Drains–underdrains to V-notch

Seepage flow quantity, and

Could indicate initiation of

E–C

a

weirs (ideally several, ‘isolating’

nature of seepage water,

cracking and/or internal

sections of dam–foundation)

e.g. clear or turbid

erosion

Porewater

Piezometers

Internal water pressure in

Leaking core, or incipient

E

pressure (E);

earthfill

instability

uplift (C)

Internal water pressure in

Instability, sliding

C

concrete or rock foundation

Collimation

Precise survey (optical or

Alignment

Movement or deformation

E–C

electronic)

Settlement

Precise survey (surface)

Crest settlement

Tilting (C) or loss offreeboard (E), e.g. core

E–C

subsidence, or foundationdeformation

{

Settlement gauges (internal)

Internal or relative settlement

}

External

Precise survey (surface)

Surface deflection

Local movement, instability

E–C

deformation

Photogrammetry (E), pendulaor jointmeters (C)

Internaldeformation or

Inclinometers,

strain:

strain gauges

Internal relative displacements

Incipient instability

E

vertical

or duct tubes

horizontal

}

Stress or

Pressure cells

Total stress

Hydraulic fracture and

E

pressure

internal erosion

a E



embankment dams, C



concrete dams.