PART 8 DAMS AND DAM SECTIONS
( First Revision)
UDC 627.82 : 001.4
@ BIS 1992
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002
April 1992 Price Groop 9
( Reaffirmed 1997 )
Terminology Relating to River Valley Projects Sectional Committee, RVD 2
This Indian Standard ( Part 8 ) ( First Revision ) was adopted by the Bureau of Indian Standards, after
the draft finalized by the Terminology Relating to River Valley Projects Sectional Committee had been
approved by the River Valley Division Council.
A large number of Indian Standards have already been printed covering various aspects of river valley
projects and some more similar standards are in the process of formulation. These standards include
technical terms, and precise definitions for these are required for avoiding ambiguity in their interpretation.
To achieve this aim, the Terminology Relating to River Valley Projects Sectional Committee is bringing
out Indian Standard glossary of terms relating to river valley projects ( IS 4410 ), being published in parts.
This Part 8 contains definitions of terms relating to dams and dam sections.
This standard was first published in 1968. The present revision of the standard has been taken up in the
light of experience gained during the last 23 years in the use of this standard. In this revision, additional
terms have been added besides modifying some of the terms so as to bring them in line with latest
In the formulation of this standard, due weightage has also been given to international co-odination among
the standards and practices prevailing in different countries. This has been met by deriving considerable
assistance from cMultilingual technical dictionary on irrigation and drainage’, published by International
Commission on Irrigation and Drainage ( ICID ) and other sources.
I84310 c-8) tl992
GLOSSARY OF TERMS RELATING TO RIVER
PART 8 DAMS_ AND DAM SECTIONS
( First Revision )
1.1 This standard contains definitions of terms
relating to types of dams, dam sections, galleries,
shafts and tunnels, joints and grouting in dam.
1.2 It does not contain terms relating to weirs,
barrages and spillways.
2 TYPES OF DAMS
2.1 Arch Dam
A curved solid masonry or concrete dam, convex
upstream, that depends principally on arch action
for its stability. The water load is mostly trans-
ferred by the arch to the canyon walls, ‘or other
abutments. It is also called ‘Arched Dam’.
2.2 Arch Gravity Dam
A curved solid masonry dam which depends upon
both arch action and gravity action for stability.
Also called ‘Curved Gravity Dam’. Arch gravity
dam has the base thickness between O-5 to 0.6
times the height of dam.
2.3 Articulated Type Buttress Dam
Same as simply supported flat slab deck dam.
2.4 Bag Dam
A low dam made of bags partly filled with soil
or boulder concrete. Bags are partly filled to per-
mit flexibility in placement,
2.5 Basket Dam
A dam composed of boulders held in woven wire
crates and piled up to form a barrier.
2.6 Beaver Type Dam
A fixed timber dam used for low heads, the bents
being of round timbers or logs with butts pointing
downstream, spacing logs laid transversely, crevi-
ces filled with gravel, covered with a plank deck,
the whole structure being fastened together with
drift bolts, and to the foundation with anchor
bolts. It is seldom used as a permanent structure.
2.7 Boule Dam
A movable dam similar to a Poiree Dam
( see 2.67 ) but with horizontal stop logs or panels,
instead of needles which span from trestle to
2.8 Brush Dam
A check dam made of brush wood usually held
in place with stakes and wire.
2.9 Bulk Head Rutt;ess Dam
A type of buttress dam ( see 2.10 ) in which the
face slab is replaced by flaring the upstream edge
of the buttresses to span the distance between
buttress walls. The flaring portion may be of
various geometrical shapes, namely, (a) massive
head; (b) round head or mushroom head; and
(c) diamond head. The buttress dams comprising
types of head classified above are named .accord-
ingly. It is also calIed ‘Round Head Buttress
2.10 Buttress Dam
A dam consisting of a water supporting upstream
face or deck, usually reinforced concrete slab,
supported by buttresses generally in the form of
equally spaced triangular reinforced concrete or
masonry walls or counterforts, that transmit the
water load and weight of the deck to the
2.11 Cantilever Buttress Dam
A flat deck dam where the slab is cantilevered
from the buttresses.
2.12 Cantilevered Steel Dam
2.13 Check Dam
A small low fixed dam, constructed of brush, logs,
timber, loose rock, masonry, or concrete, in an
eroded channel to reduce the slope of the water
flowing therein during high stages, and also the
resulting velocity, thereby preventing excessive
scour and erosion and inducing deposition. A
reduction in the size of flood peaks of erosion, and
sometimes an increase in low-water flow due to
increased ground storage often result from build-
ing a check dam. Such dams are also used to
retain debris. They usually are built of inexpensive
and temporary materials where dependence for
ultimate protection is placed on vegetative cover.
IS 4410 ( Put 8 )
2.14 Coffer Dam
It is a temporary structure to exclude water or
water and earth from a specific area to facilitate
2.15 Columner Buttress Dam
A type of deck dam in which the massive buttres-
ses are replaced by a series of inclined columns.
2.16 Composite Dam
A concrete/masonry wall with rockfill or earth-
backing in downstream.
2.17 Composite Earth Dam
An earth dam consisting essentially of an inner or
enclosed impervious section supported by two or
more outer sections of relatively pervious material.
It is also called ‘Multiple Zoned Earth Dam’ or
‘Zoned Earth Dam’.
2.18 Conoidal Dam
It is a modification of cupola arch buttress dam
and has some of the characteristics of the hollow
gravity dam and some of those of multiple arch
dam. The upstream face is a plane slightly in-
clined to the vertical; the downstream face is a
conoidal surface generated by straight lines, which
where they touch the horizontal at the crest are
orthogonal there-to and repose on a directrix
drawn in a horizontal plane ( see Fig. 1 ).
FIG. 1 CONOIDAL DAM
2.19 Constant Angle Arch Dam
It is a special type of variable centre dam in
which the central angle of the arches are of
approximately the same magnitude at all elevation
( see Fig. 2 ).
2.20 Constant Centre Arch Dam or
Constant Radius Arch Dam
A type of arch dam whose arch centres for the
upstream face and the downstream face are coin-
cident with the axis centre at all elevation. A
profile of these centres is a vertical straightline
and the arches are of uniform thickness. All canti-
levers are of identical shape, varying only in base
elevation ( see Fig. 3 ).
2.21 Constant’ Centre Dam
2.22 Core-Wall Type Rockfill Dam
A rockfill dam in which a core wall of steel,
concrete ( plain or reinforced ) or compacted
earth is placed in the centre, and the rockfill is
dumped on both sides.
2.23 Cored Gravity Dam
It resembles hollow gravity dam in principle ex-
cept that hollows are provided along contraction
joints and not in the middle of the section ( see
Fig. 4 ).
A timber dam consisting of a series of cribs or
rectangular cells made of square or round timbers,
drift-bolted together, filled with broken rock or
boulders, with a upstream facing and deck covered
with heavy planks to provide watertightness.
2.25 Cupola Arch Buttress Dam
Here the upstream face of the buttress dam con-
sists of semi-cupolas of ovoidal form of reinforced
concrete. F’urther modification of this dam is
2.26 Cupola Arch Dam
Same as double curvature arch dam.
2.24 Cribe Dam
2.28 Debris Dam
2.29 Detention Dam
2.30 Direct-Strutted Steel Dam
A type of steel dam in which the load is trans-
ferred from the deck to the foundation through
inclined struts ( see Fig. 5 ).
A barrier constructed across a river or natural
watercourse for the purpose of: (a) impounding
water or creating reservoir ( see 2.48 ); (b) divert-
ing water there from into a conduit or channel
for power generation and or irrigation purpose;
.(c) creating a head which can be used for genera-
tion of power; (d) improving river navigability;
(e) retention of debris; (f) flood control;
(g) domestic, municipal and induses; (h) preser-
vation of wild life and pisciculture, (j). recreation,
A dam buiit across a stream channel to catch and
retain debris, such as sand, gravel, silt and
A dam whose principal purpose is to temporarily
detain all or part of the runoff and enable its
release at controlled rates, as and when required.
FIG. 2 CONSTANTANGLB ARCH DAM
FIG. 3 CONSTANTRADIUSARCH DAM
FIG. 4 COREDGRAVITYDAM
FIG. 5 TYPICAL DIRECT-STRUTTEDTYPE STBBL_DAM
“2.31 Diversion Dam 2.32 Dome Dam
A fixed dam built far the purpose of diverting
part or all of the water from a stream out of and A curved masonry, or concrete
away from its course. It is also called ‘Diverting stream that depends principally
Weir’. for its-stability ( see Fig. 6 ).
dam convex up-
on dome action
2.40 Free Deck Dam _
A flat deck dam where the slab is freely supported
on the buttress.
FIG. 6 DOME DAM
2.33 Double Curvature Arch Dam
It is an arch dam which is curved in plan and in
elevation with under cutting of the heel and in
most .instances, downstream overhang near the
crest. It is also called Cupola Arch Dam’.
2.34 Earth Dam
2.41 Gravel Fill Dam
It is a dam composed of gravel or shingle with
the downstream part made of relatively coarse
material, and the upstream or water side part
made of finer gravel and sand.
2.42 Gravity Dam
A solid concrete or masonry dam so designed and
shaped that its weight is sufficient to ensure stabi-
lity against the effects of all imposed forces ( See
Fig. 9 ).
2.42.1 High Gravity Dam
A gravity dam above 90 m in height is called
high gravity dam.
2.42.2 Low Gravity Dam
A gravity dam less than 30 metres in height is
called low gravity dam.
2.42.3 Medium Height Gravity Dam
A gravity dam between 30 metres and 90 metres
in height is called medium height gravity dam.
2.43 Hollow Base Dam
Same as hollow gravity dam, where a big cavity
is left only in the bottom portion
4 Hol!s_=; Dam
2.35 Fabri Dam
It is hollow dam of reinforced rubber. The dam
is inllated and deflated as required by use of air
2.36 Fired Deck Dam
A flat deck dam where the slab is integrally cast
with the buttress. Also called ‘Fixed Slab Buttress
2.37 Fixed Slab Buttress Dam
2.36 Flat Slab Deck Dam
This type of dam is made of a flat reinforced
concrete slab, which transmits water pressure to a
series of parallel buttress which rest directly on
the foundation or upon a concrete slab resting on
the foundation material ( see Fig. 8 ).
2.39 Framed Dam
A low fixed dam generally built of timber frames
to form a water face, supported by struts.
A modification of buttress dam in which the
buttresses are grouped or joined together leaving
2.45 Hollow Gravity Dam
It is a structural refinement of the solid gravity
dam in which some concrete from the low stress
areas of solid dam is removed to reduce uplift
pressure and a slop is provided to upstream face
of the dam to take advantage of the water load
for improving stability. The base is also widened
in direction of the thrust to improve stability
against overturning and sliding ( see Fig. 10 ).
2.46 Homogeneous Earth Dam
An earth dam composed of a single type of mate-
rial, except for protective material on the exposed
2.47 Hydraulic Fill Dam
An earth dam, in the construction of which all or
most of the materials have been transported by
agency of water to the dam and placed in the dam
by dredging, sluicing, or pumping. Generally, for
greater imperviousness, the fine material in the
sluiced earth is segregated and deposited along
the centre of the dam to form a core.
IS 4410 ( Part 8 ) : 1992
2.48 Impounding Dam
2.49 Large Dam
A dam above 15 m in height
lowest portion of the general
the crest or a dam between
height, provided it complies
the following conditions:
a) The length of crest of
less than 500 m;
measured from the
foundation area to
10 m and 15 m in
with at least one of
the dam to be not
b) The capacity of reservoir formed by the
dam to be not less than 1 million ms;
c) The maximum flood discharge dealt with
by the dam to be not less than 2 GO0ma/
d) The dam had specially difficult foundation
e) The dam is of unusual design.
2.50 Landslide Dam
An obstruction formed in the stream Bow due to
natural causes, like huge rockfalls, landslides, or
snow avalanche from the side slope resulting in
complete or partial blockade.
An earthen embankment extending generally
parallel to river channel and designed to protect
the area ,behind it from overflow by flood waters.
2.52 Loose Rock Dam
A dam constructed of variable size rocks, without
mortar, usually dumped in place without any
particular effort at packing sorting or arranging.
UPSTREAM BLANKET DOWNSTREAM SHELL OR
FIG. 7 TYPICAL EARTH DAM
UPSTREAM ELEVATION CROSS SECTION
FIG. 8 FLAT SLAB DECK DAM
FIG. 9 GRAVITY DAM
FIO. 10 HOLLOW GRAVITYDAM
2.53 Lifting Dam
A dam of any type of construction meant to raise
the water level for diversion purposes without any
2.54 Masonry-cum-Earth Dam
A dam comprising portion of earth and masonry
along its length ( spillway, not included ).
2.55 Masonry Dam
A dam composed of one or more of the following
material brick or stone masonry.
2.56 Massive Head Buttress Dam
2.57 Medium Arch Gravity Dam
It is an arch dam where the thickness of base is
between O-2 times to O-3 times the height.
2.58 Modified Homogeneous Earth Dam
An earth dam, in which small amounts of pervi-
ous material selected to control the action of
seepage are suitably incorporated in an otherwise
2.59 Multiple Arch Ram
A buttress dam composed of a series of inclined
arches supported by buttresses or piers. The load
is transferred from the arches to the foundation
through the buttresses ( see Fig. 11 ).
2.60 Multiple Dome Buttress Dam
A buttress dam in which massive buttresses spaced
far apart support a set .or series of domes on which
the water rests ( see Fig. 12 ). It is also called,
‘Multiple Dome Dam’.
2.61 Multiple Dome Dam
7 BUTTRESS 1
III II CROWN
L INCLINED BARREL
-- -_ ------ BUTTRESS
BUTTRESS BRACING? m//
CROWN OF ARCH
FIG. 11 MULTIPLE ARCH DAM
Multiple Zoned Earth Dam 2.66 Overnow Dam
2.63 Non&ver Flow Dam
2.67 Poiree Dam
The dam portion which does not allow to escape
Aood waters by overtopping is called non-overflow
2.64 Non-Rigid Dam
A dam constructed with non-rigid materials or
materials like earth rockfill, etc.
2.65 Overfall Dam
A dam constructed with a crest to permit the over-
flow of water. Also called ‘Overflow Dam’ and
A dam consisting of a curtain of timber needles
supported at the bottom by a sill and at the top
by a beam carried by moving steel trestles.
2.68 Poly-Centered or Three-Centered Dams
These dams are variable centre dams in which
the location of centres and radii associated with
them also x&y horizontally to produce dams
with elliptically shaped or multicentered arch
IS 4410 ( Part 8 ) : lS!E
increases the initial compressive stress in the
upstream portion of the dam allowing for thinner
cross section than those for gravity dams. The
post-tensioning bars or wires are arranged in
groups, and located in holes or shafts, and are
anchored into the foundations ( shaft anchorage )
( see Fig. 13 ).
2.70 Rigid Buttress Dam
A dam having upstream water supporting members
constructed monolithically with the buttresses
with no provisions for unequal foundation settle-
ment or for expansion and contraction between
adjacent bays. Examples of the rigid type are
multiple arch and continuous deck type ( see
Fig. 14 ).
2.69 Prestressed Dam
A dam comprising of concrete which, by post-
tensioning with high tensile steel bars or wires,
FIG. 12 MULTIPLEDOMEDAM FIG. 13 A TYPICALPRESTRBSSEDDAM
FIG. 14 RIGID BUTTRESS DAM
2.71 Rigid Dam
A dam constructed with rigid material such as
masonry, concrete, steel or timber.
2.72 Rockfill Composite Dam
A rockfill dam consisting of a rockfill on the
downstream side and an earthfill on the upstream
side; the former for stability principally, the latter
for both imperviousness and stability.
2.73 Rockfill Dam
A dam composed of rock, either dumped in lifts
or compacted in layers as a major structural
element. An impervious membrane is used as the
water barrier and can be placed either within the
embankment or on the upstream slooe ( see
Fig. 15 ).
A movable dam consisting of a large steel cylinder
placed across the waterway between piers of
abutments and arranged to be rolled up clear of’
the stream flow on an inclined rack track.
2.76 Round Head Buttress Dam
a) &vtral’Earth Core
d) Central Thin Membiane
2.74 Relled Earth Dam
A dam in which selected materials are placed in
thin layers and compacted by rolling at proper
moisture content. It can be a zoned earth dam or
a homogeneous earth dam.
2.75 Rolling Dam
b) Sloping Earth Core c) Upstream Core
e) &e&am Thin Membrane or Deck f) Dam with Rubble Retaining Zone
FIG. i5 ROCRPILL DAM TYPES
Z-77 Rubble Dam
A dam constructed of rocks laid in place, without
2.78 Sausage Dam
A low dam constructed of cylinders of loose rock
formed by wirenet wrapping. The cylinders are
laid in either a horizontal or a vertical position.
Such dams are not impervious and are used
primarily to reduce erosion, retard debris, etc.
2.79 Semihydraulic Fill Dam
An earth dam in the construction of which the
material has been transported by some means
other than water, and some of it has been moved
into place by the agency of water.
2.80 Sdmirigid Dam
An intermediate class of dam between rigid and
non-rigid type like rockfill dam.
2.81 Single Centred Dams
These dams have one set of lines of centre on the
reference plane. Both sides of each face are
described by the same circular arc.
2.82 Single Curvature Dam
An arch dam which is curved in plan only.
2.83 Small Dam
A dam less than 15 m in height and which does
not fulfil any of the conditions of a large dams.
I.S4&10 (,Pwt 8 ) :: 1592
2.84 Solid Gravity Dam
2.85 Spillover Buttress Dam
Where flood water is allowed to be passed over,
buttress ( seeFig. 16 ).
2.86 Spillway Dam
2.87 Steel Dam
A dam built of steei deck supported on inclined
steel struts. There are two general types of this
dam: (a) ‘Direct-Strutted Steel Dam’ ( see 2.90 )
in which the load is transFerred Corn the deck to
the foundations through inclined struts ( ree
Fig. 5 ), and (b) ‘Cantilevered Steel Dam’
( see2.12 ), which consists of variations of the
direct strutted type, in which the section of the
bent supporting the upper part oi the deck is
formed into a cantilever truss ( see Fig. 17 ).
2.88 Storage Dam
This dam impounds water in periods of surplus
supply for use in periods of deficient supply. These
periods may be seasonal, annual or longer.
2.L9 Straight Gravity Dam
A gravity dam straight in plan.
2.?0 Thick Arch Dam
It is an arch dam where the thickness of base is
between O-3 times to 0.5 times the height.
FIQ. 16 SPILL &'ER BUTTRESSDAM
IS ‘4410 ( Part 8 ) I 1992
FIG. 17 TYPICAL CANTILBVBRTYPB STEEL DAM
2.91 Thin Arch Dam
It is an arch dam where the thickness of base is
less than O-2 times the height.
2.92 Til&ng Dam
An overflow dam so constructed that a top section
will tilt and allow the passage of excess water;
sections are set to tilt at various elevations of the
2.93 Timber Dam
A dam constructed of framed timbers. The dam
may be of cellular or crib construction, filled with
rock to give it stability, or it may attain such
stability through its form of design.
2.94 Timber A-Frame Dam
A fixed dam, usually low in height, built of
squared timbers with a plank facing, and not
filled with rock. The bents or’ buttresses are
framed like the letter ‘A’ lying on its side, with
apex upstream, one side forming a sill and the
other the support for the deck. The deck usually
makes an angle of less than 30 degrees with the
2.95 Truss Buttress Dam
A type of deck dam in which the massive butt&-
ses are replaced by reinfored concrete trusses to
support the deck slab.
2.96 Two-Centered Dam
These dams have two sets of lines of centres, one
set for each side of the dam. The two sets are
coplanear on the reference plane. Each face of an
arch element is described by two circular arcs
compounded at the reference plane.
2.97 Variable Centre Dam
An arch dam whose arch centres for either or
both the upstream face and the downstream face
vary in location with respect to axis centre at
different elevations. The arches may be of uniform
thickness or variable thickness with or without
fillets. Cantilevers vary in shape and thickness at
different locations within the dam according to
the difference in curvature between the arches
and according to the kind of arches used ( SM
Fig. 18 ).
2.98 Variable Radius Arch Dam
2.99 Wicket Dam
A movable dam consisting of a sill and a number
of wickets or rectangular panels of wood or iron,
hinged on the sill and held up nearly vertical by a
hanged prop that has a footing on the sill and
can be tripped, dropping the wickets flat on the
3 TERMS RELATING TO DAM SECTIONS
3.1 Abutment of a Beam Element
It is the surface at either end of the beam, which
contacts the rock of the canyon wall.
3.2 Abutment Pads
It is a structure between arch dam and their
A floor or lining of concrete, timber, stone, etc, to
protect a surface from erosion, such as the
pavement below chutes, spillways, or the toe of
3.4 Arch Abatment-
The abutment of an arch element is the surface
at either end of the arch, which contacts the rock
of the canyon wall. Arch loads are transferred
through the arch abutments to the canyon walls.
3.5 Arch Cantilever Section
It is a vertical section taken normal to the extra-
dos usually oriented with the reservoir on the
3.6 Arch Centre Line
The locus of all median points of the thickness of
an arch section.
3.7 Arch Element
An arch element, or arch, is a portion of a dam
bounded by two horizontal planes at distances of
one unit apart.
3.8 Arch Section
A section representative of an arch dam as it
would appear if cut by a horizontal plane.
3.10 Axis of Dam
The olane or curved surface arbitrarilv chosen bv
the design or approach as
cross section to which the
of the dam can be referred.
a line in plan or in
iI?+4410 ( Part 8 1;‘: i999
3.11 Beam Element or B-m
It is a portion of a gravity dam bounded by two
horizontal planes one metre apart.
3.12 Beam Section
A horizontal section through the dam.
Any in-situ rock underlying the overall burden
A cover of pervious, semi-pervious or impervious
The covering of one type of material by a layer of
another type of material.
A curved surface provided at the toe of an
overflow dam to deflect the overflowing
water in such a manner as to reduce erosion
at the toe of dam.
The transition curve between the down-
stream face of an overflow dam and its
3.17 Cantilever Elements
The cantilever element, or cantilever, is that
portion of a dam, which is contained within two
vertical radial planes or two vertical planes normal
to the dam axis spaced a unit distance apart at
the axis. Cantilevers of arch dams, other than
one of the constant-centre typ, have warped sides
owing to the fact that the arch centre line radii
are not the same at all elevations. The crown
cantilever is located at the point of maximum
3.18 Cantilever Section
It is a vertical section taken normal to the axis,
usually oriented with the reservoir on the left.
3.19 Canyon or Canon
A deep valley with high steep slopes generally
with a stream at the bottom. Canyons are charac-
teristic of regions where, owing to aridity or to
great slope, the downward cutting of the stream
greatly exceeds weathering. The width at the top
is generally several kilometres and at the bottom
about that of the stream distinguish by its great
size and rugged steep slopes.
3.20 Canyon Shape
Same as ‘Valley Shape’.
Its 4410 ( Part 8 ) t 1992
3.21 Canyon Shape Factor
It is the ratio of the perimeter of the foundations
and abutments of a dam measured along its axis
and the maximum height of the dam.
3.22 Canyon Wall
It is the side face. of the long narrow canyon
valley along which the dam abutts.
3.23 Central Angle of Arch Dam
Central angle of arch is the angle bounded by lines
radiating from the arch extrados centre to points
of intersection of the arch centre line with the
abutments ( see Fig. 2 ).
3.24 Construction Sluice
It is an opening through the body of the dam for
passing or diverting water during the construction
period of dam.
3.25 Control House
A structure usually built at the top of the shaft
and employed as a means of access to the gate
chamber. The house usually shelters the remote
control mechanism, a hoist, generator set, ventila-
ting system, heater, gate height indicator, etc.
A wall of concrete or masonry, sheet piling, or
compacted puddled clay built inside an earth or
rockfill dam to reduce percolation. It is also called
‘Core Wall’ ( seeFig. 7 ).
3.27 Core Wall
The line or area defining the top of the dam or
the overflow section of a spillway.
3.29 Crest Length
The length as measured along the crest of the
3.30 Crest Lavel
The elevation of the crest of a dam above mean
A wall or diaphragm of concrete or steel, or a
trench filled with impervious earth or grout cur-
tain, extending into the foundation of a dam, and
either making a watertight connection with the
dam or its impervious facing or extending into
the body of the dam a considerable distance; its
purpose is the prevention or reduction of passage
of water under the dam and the foundation mate-
rial or through the upper layers of the foundation
material ( see Fig. 7 ).
3.32 Cutoff Buttress
Cross walls projecting into embankment from
spillway abutments, power-house walls, or other-
concrete walls extending through the structure in..
an upstream and downstream direction.
3.33 Cutoff Collars
In all closed conduit layouts, seepage of water.
along the contact plane of the outlet conduit and
the dam embankment is minimized by the cons-
truction of projecting fins or cutoff collars around
the exterior circumference of the conduit parti-.
cularly through the upstream and the central.
portion of the impervious section of the dam.
3.34 Cutoff Trench
An excavation in the base of a dam to be filleck:
with relatively impervious material to reduce
percolation through the foundatioa.
3.35 Cutoff Wall
3,36 Dam Axis
3.37 Downstream Projection
It is the horizontal distance from the intrados te,
the axis on a line normal to the extrados,
3.38 Downstream Shell or Downstream Fill
3.39 Downstream Toe
Junction of the downstream slope or face of a
dam with the ground surface or downstream river-
3.40 Drainage Wells
‘Openings between the watertight arches and the.
supporting mass in a dam with levy-type facing.
3.41 Drainage Filter
3.42 Drain Well
A deep cylindrical drain located in the founda-.
tions of a dam or downstream of it to relieve the
seepage pressures in pervious strata too deep to be
reached by trench drains, and to drain localized
concentrations of seepage, where a continuous
trench of pervious blanket is not warranted. They~
are also employed to correct developed bed
3.43 Elevator Tower
Tower containing lifts
at different elevations.
to give access to galleries.
It is the curved upstream surface of horizontal
.A fillet is an increase in thickness of a dam at and
near the abutments of the arches or the base of
the cantilevers. Fillets are usually placed at the
downstream face, but may also be used at the
upstream edge of the base of the maximum canti-
One or more layers of porous materials so arran-
ged as to prevent movement of finer soil particles
towards coarser strata by seepage flow of water
( see Fig. 7 ).
Portion of the foundation of a structure that
transmits loads directly to the soil.
IS 4410 ( Part 8 ) : 1852
3.54 Hoisting Chamber
A chamber built to house remote control hoisting
3.55 Horizontal Drainage Blanket
A blanket of pervious material constructed at the
foundation from downstream toe of the impervious
zone to the landside in a levee or downstream side
of an earth dam, to permit the discharge of see-
page flow without movement of finer soil particles
and to minimize the possibility of piping failure,
either of the blowout or subsurface erosion type.
It is also called ‘Pervious Blanket’ or ‘Drainge
3.56 Hydraulic Height
The hydraulic height is the difference in elevation.
between the lowest point in original stream bed
at the axis of the dam and the highest controlled
3.57 Impervious Blank&
3.48 Free Board
A blanket which is impervious.
The vertical distance between a specified water 3*58 Jnsu1atin8 Wa’1
.surface and top of the non-overflow section of the A thin wall of reinforced concrete provided along
-dam. the downstream face of a dam and at a little
3.49 Gate Chamber of Sluice Well
An opening located within the abutment or main
body of the dam or the dam embankment within
which the regulating gates or emergency gates are
installed. The lower portion of the chamber provi-
des an anchorage for the gates and liner, while
the upper portion furnishes working space for the
removal oft he gate leaf and other parts for repair,
and for the installation of the necessary control
mecharriaGi& The gate chamber is usually located
upstream of the axis olthe &SE
a) A small canyon,
b) A narrow passage between mountains,
c) A ravine.
The upstream edge of the base of a masonry dam.
It is also called ‘Upstream Toe’.
distance from it with a view to protect it from
frost damage in cold countries.
It is the curved downstream surface of horizontal
3.60 Inverted Filter
A 1a)er or layers of pervious or semi-pervious
material having a controlled gradation to provide
drainage and prevent movement of finear soil
particles due to seepage flow of water. It is also
ch!!:d ‘Protective Filter’.
3.61 Irrigation Sluice
It is an opening through the body of ihe dam for
passing water for irrigation purposes.
3.62 Key Wall
A cutoff wall extending from the cutoff trench
into the bed rock or impervious subsurface
3.52 Heel Line 3.63 Length of Arch Dam
The line joining the upstream slope or face of a It is the length along a curve which is concentric
dam with the valley floor or upstream blanket. It
is also called Upstream Toe Line’.
with the extrados and passes through the midpoint
of the arch thickness at the crown.
3.53 Height of Cantilever 3.64 Length of Dam
It is the vertical distance between the base eleva- The extent of barrier in dam and integral features
tion of the cantilever section and the top of dam constructed between excavated abutments. The
which may or may not be the top arch. length is measured along the axis of the dam at
lS.clJlO ( Part 8 ,J,.: 1992
the elevation of the top. of the main body of the
dam or of the roadway surface exclusive of any
abutment spillway. If the spillway lies wholly
within the dam and not in any area especially
excavated for the spillway, the length should be
the length along the axis extended through the
spillway to the abutment contacts. Also called
3.65 Line of Arch Centres
A line passing through the arch centres in plan
or profile. Arch centres are located so that they
will be on smooth profile curves in a vertical
plane, In the case of a constant centre type of
arch dam, a single vertical line will be the locus
of the arch centres. For variable centre dams,
separate profile curves will be the loci of arch
centres for the upstream face, the centre line, and
the downstream face. In the case of symmetrical
layouts, the vertical plane through the arch cen-
tres will generally intersect the dam at the place
of maximum deflection ( see also 3.6 ).
3.66 Main Body
The structural part of a dam above foundation.
3.67 Maximum Base Width
Horizontal distance between the outer points of
the heel and toe of the cross section of a darn or
3.68 Maximum Height of Dam
a) The portion of spillway crest of the dam
projecting upstream for efficient water
A cutoff extending into the underlying stratum,
but not reaching an impervious subsurface
3.71 Perforated Cutoff
A nonwatertight cutoff made of material such as
steel sheet piles. It is also called ‘Semi-impervious
3.72 Positive Cutoff or Complete Cutoff
A cutoff extending to or into the bed rock or into
impermeable subsurface stratum.
3.73 Pressure Relief Well or Drain Well or
A profile is a developed elevation of the iptersec--
tion of the dam with the original ground surface,
rock surface, limit of excavation, or any other.
surface along a designed line, such as the axis, or
the upstream of downstream toe. Profiles are
commonly classified as U-shaped or V-shaped,-
with variation between these two classifications.
3.75 Protective Filter
3.76 Pulvino ( Cushion )
It is a type of abutment pad provided to protect
abutment rock against weathering. It acts as a
transition structure between the arch and the rock,..
distributes the stresses on the rock or bridge over
areas and of weak rock and also smoothens out.
any irregularities in the foundation.
3.77 Relief Well
Material, such as rock, concrete blocks or mattres-
ses, placed on the bottom or banks of a river to-
prevent or minimize erosion.
3.79 Riverside Blanket
3.80 Rock Toe
The downstream toe of an earth dam or other,
structure constructed of rock materials.
3.81 Section of an Arch Dam
b) In an arch dam, the port
beyond the width of top ar
3.82 Semi-impervious Cutoff
3.83 Service Outlet
Outlets provided in the body of the dam through
which water is drawn off for actual use. These are
provided with trash racks.
A component of an arch dam constructed of-
pervious or semi-pervious materials upstream and
downstream of the core or membrane. The up-.
stream portion is called ‘Upstream Shell’ and the
downstream portion ‘Downstream Shell’. Shell is-
also called ‘Shoulder’ ( see Fig. 7 ).
3.86 Shot Concrete Cutoff
It is a type of abutment pad; it varies in depth
according to requirements of symmetry of the
arches and excavation of the abutments and is
placed as an integral part of the dam.
A surface layar of soil matted or held together by
roots, rhizomes and stolons of grasses and other
herbs ( see Fig. 7 )._ This is normally used in the
downstream surface of earth dam for preventing
rain cuts and is also known as ‘Turfing’.
a) A conduit, fitted with a gate, for carrying
water at high velocity.
b) An opening in a structure through which
anything flows, for example, water, ice or
c) To cause water to flow at high velocities
for wastage, for purpose of excavation,
ejecting debris, transporting ways, etc.
3.90 Sluicing Outlet or Desilting Sluice
Outlet in the body of the dam, used for scouring
or sluicing out settled material from the reservoir.
3.91 Stoped Cutoff
Cutoff constructed by utilising underground
mining methods for excavation, then backfilling
the excavation with concrete or other selected
3.92 Stub Concrete Cutoff
Cutoff employed in conjunction with a level rock
foundations or with a deep soil trenches cutoff
where a good seal of earth on rock is difficult to
obtain. Its purpose is to increase to path of
seepage and prevent leakage along the rock-soil
3.93 Structural Height of Dam
It is the vertical distance between the lowest
point in foundation and top of the dam. The
structural height of an’ earth dam is the vertical
distance between the top of embankment and the
lowest point in the excavated foundation area,
including the main cutoff trench, if any, but
excluding small trenches or narrow back-filled
areas whose width is less than 10 m. The top
elevation does not include the crown of any road-
way over the dam. The structural height of a
masonry dam is the vertical distance between the
top of the dam and the lowest point of the
excavated foundation area, whose width is less
than 10 m. The top of the dam is the crown of
the roadway, if a roadway is taken over the dam,
otherwise it is the level of the walkway.
3.94 Supporting Ma8s.
The portion of the body of a dam supporting the
3.95 Thickness of Arch Dam
It is the length of a line along an extrados radius
from the upstream to the downstream face which
passes through the point.
3.98 Tltickness of Dam
Thickness of a dam at any point is the distance
between the upstream and downstream face along
a line normal to the axis through the point.
3.97 Thrust Block
It is an artificial abutment and can be used:
i) to reduce length of an arch near the top
of a dam canyons that widen rapidly;
ii) to reduce non-symmetry;
iii) to spread the stress over wider area in case
of weak abutment rock;
iv) to serve as an abutment where no natural
rock abutment exists;
v) to accommodate the spillway and to locate
conduits where situation requires.
3.98 Toe Drain
A drain constructed at the downstream toe of an
earth dam to collect and drain away the seepage
through the dam and its foundation ( see Fig. 7 ).
3.99 Top Width
Width at the top of the dam.
3.100 Transition Filter
A component of an earth dam section ( with core )
consisting of intermediate grade of material placed
between the core and the shells to function like a
filter, preventing lateral movement of fines from
the core ( see Fig. 7 ).
3.101 Transition Zone
It is the part of the section of an earth dam
occupied by the transition filters placed between
two zones of an earth dam so as to prevent the
lateral movement of finer particles towards the
3.102 Trench Drain
A drain provided in the foundations of a dam to
intercept seepage. When placed immediately after
a cutoff, it relieves any pressure that might deve-
lop from possible ineffectiveness of the cutoff.
3.101 Upstream Blanket
An impervious blanket constructed from the
upstream toe of impervious zone towards the
* 4~1.0 ( Part.8 ) : 19%:
upstream of an earth dam or towards riverside of
a levee ( then called ‘Riverside Blanket’ ) where
subs&&m’ is pervious, to control seepage by
increasing the resistance to seepage entry into the
pervious substratum, thereby decreasing’ both
seepage flow and excess pressure downstream side
of the earth -dam or landward side of the levee
( see Fig. 7 ).
--. I :‘. .-: ,_ ?.- ‘; _
A passageway in a dam for obtaining access to
interior parts, or to carry pipes or. t.o.,-house-
4.7 Gate Gallery
3.105 Upstream Shell or Upstream Fiil
Gallery, made in a dam, to provide access to and
room for, the mechanical equipment required for-
the operation of gates in outlet conduits, power-
penstocks or spillway crests.
4.8 Grouting Gallery
3.106 Upstream Toe
3.107 Upstream Toe Line
3.108 Valley Shape
It is the ratio of the width of the valley at crest
level of dam to the depth of the valley below
crest level, it is also called canyon shape.
Gallery provided in a dam to locate the supply,.
return and vent headers of the grout piping system;
also the piping system for artificial cooling of the-
blocks terminates in the galleries.
4.9 Inspection Gallery
Gallery made in a dam to provide access to the-
interior of the mass in order to inspect the struc-
ture and study the structural behaviour of the
dam after completion. Foundation, drainage gate
and grouting galleries also serve as inspection
galleries ( see Fig. 9 ).
It is that smaller segment of a section of an arch
which, for ease of computation, is assumed to
have constant thickness.
4.10 Plum-Line Shaft or Collimator Shaft
4 TERMS RELATING TO GALLERIES AND
OTHER OPENING IN THE DAMS
A shaft located near the maximum section of a
dam in order to make observations of the move--
ments of the dam with respect to the base.
4.1 Access Gallery
A horizontal gallery connecting the gallery system
in the dam with the downstream face or features
outside the dam, such as power house or gate
house. Also called ‘Adit’ or ‘Entrance Gallery’
( see Fig. 9 )
4.3 Drainage Gallery
Vertical openings provided in the dam at suitable
places for various purposes, such as for location
of headers of artificial cooling system, accommo-.
dation for measuring devices, for connecting).
galleries by stairway, for elevator movement and
for hoisting equipment for inspection purpose
4.12 Stilling Well Shaft
A special shaft, sometimes, included in the design
of a dam, open to the reservoir below minimum
reservoir level and containing a floating mecha-
nism to record reservoir fluctuations,
A gallery in a masonry dam, parallel to the crest
to intercept seepage from the water face and con-
duct it away from the downstream face.
4.4 Entrance Gallery
4.13 Spillway Tunnel
A tunnel used as a spillway outlet.
4.14 Weep Holes
4.5 Foundation Gallery
A gallery providing drainage for water percolating
from the upstream face or seeping through the
foundations in a dam, generally extending the
length of the dam near the rock surface, conform-
ing in elevation to the transverse profile of the
canyon; in plan it is near and parallel to the axis
of the dam. It is from this gallery that the holes
for the main grout curtain are drilled and grouted,
and also from which foundation drain holes are
Holes used for reduction of uplift pressure under-
aprons and excessive pressure behind walls.
5 TERMS RELATING TO APPURTENANT
WORKS TO A DAM
5.1 Bye-Pass Outlet
It is a sluice provided in a dam to bye-pass water
to flow from reservoir to canal or river down--
stream, when power house is not functioning.
5.2 Divide Wall
A wall extending along the spillway to separate:
overflowing water, wherever necessary.
.5.3 Drainage Hole .,
Holes drilled into the dam foundations for reliev-
ing uplift pressures.
5.4 Emergency Gate
Gates used for controlling flow through sluices
when any repairs or maintenance or both are
required to be carried out to service gates. These
are generally designed for full gate opening.
5.5 Fish Ladder
Structure constructed for allowing fish from river
downstream pass up into the reservoir.
Pressure pipes usually made of steel which convey
water from the intake to the turbine in hydro-
Concrete or masonry structure constructed over
the spillways for supporting bridge decking, spill-
way gates and hoist operating mechanism.
5.8 Power House
A building housing the generating and controlling
equipment of a hydroelectric power generation
5.9 Retaining Wall
Concrete or masonry wall constructed to retain
backfill or water.
5.10 Sluice Gate or Service Gate
Gates used for allowing water to flow through,
from the reservoir to downstream at a controlled
5.11 Training Wall
Concrete or masonry wall constructed on overflow.
section of the dam to guide the spillway water.
5.12 Trash Rack
A grill or cement over at intake openings for
preventing the entry of suspended or floating
material into the water conductor system. Trash
for fine/coarse openings depending upon the
nature of the debris to be included.
6 TERMS RELATING TO JOINTS
6.1 Asphalt Seal
Asphalt filler in a contraction or expansion joint
filled with asphalt to make it watertight.
The portion of a dam between two transverse,
joints constructed normal to the axis.
fS4irl-O.( Part 8 JI 1992
6.3 Closure Block or Closure Gap
Closing gaps are provided in between blocks for
adverse conditions due to temperature effects,
foundation requirements, unusual size of the struc-
ture and in stage construction. These are named
as shear slots twist slots depending upon the
6.4 Construction Joint
The interface between the t&o successive placings
of earth masonry or concrete where bond ( and
not permanent separation ) is intended. These
are classified into horizontal joints, transverse
joints and longitudinal joints ( see Fig. 9 ).
6.5 Contraction Joint
A joint provided ‘to localise and minimize develop
ment of cracks due to drying shrinkage and
6.6 Expansion Joint
A joint provided in exposed members between
fixed points to permit longitudinal expansion and
contraction when changes in temperature occur,
and to permit vertical movement where differen-
tial settlement is anticipated.
6.7 Grout Stop
A type of waterstop to confine the extent of
grouting used to seal joints.
6.8 Horizontal Joint or Construction Lift
A joint introduced between the lifts to provide
sufficient cooling between pours.
A break between two pours of concrete done at
some interval of time; or a small open space
forming a complete plane of separation between
component of the structure with relation to trans-
mission of stresses.
6.10 Joint Drain
Vertical drains provided in transverse or construc-
tion joints as a precaution against development of
excessive pressure in the joints during the cons-
truction period and against seepage of reservoir
water through the joints during the operating
period ( see Fig. 9 ).
6.11 Keyways or Offsets
Indentations or projections of some geometrical
shape built on, or formed into, poured surfaces to
provide a degree of integral action with subsequent
The height, which is poured continuously at any
time and over which other lift is poured after
sufficient time is allowed for the pour to cool.
35 4410 (:Part 8 ) t 1892
6.13 Longitudinal Construction Joint
6.14 Longitudinal Joint
a) A joint in the longitudinal direction of the
dam or parallel to the axis of the dam and
offset at the transverse joints to form a
longitudinal row of staggered columns,
b) Joint parallel to the lines of principal
stress. It is also called ‘Longitudinal Cons-
6.15 Perimetral Joint
It is a joint provided between the dam and the
foundation pad or pulvino, commonly knoivn as
pulvino perimetral joint. This joint is provided
for lower ‘and better distribution of stresses. It
also relieves tensile stress in the abutment extrados.
6.16 Polyvinyl Chloride Seals ,, .’
A type of seal manufactured in different shapes
from the polyvinyl chloride material.
These are used to prevent the leakage of water
from the reservoir to the downstream face through
transverse construction joints between construction
6.i8 Sealing Strips
6.19 Shear Key or Shear Slot
These are regular projections provided in joints
in dam for transfer of load from one block to
other through shear. The shear keys in transverse
joints are designed to transfer horizontal shear
and those in longitudinal joints are designed to
take vertical shear.
6.26 Transverse Contraction Joint .
6.61 Transverse Joint
A joint provided normal to the axis of the dam
and extending entirely through the structure
dividing it ( structure ) into separate blocks, with
a view to preventing haphazard transverse crack-
ing due to contractions of concrete. Also called
‘Transverse Contraction Joint’.
6.22 Transverse Joint Seals
Device provided in the transverse joint to prevent
leakage of water from the reservoir. These seals
are of copper, rubber, etc. Also called ‘Sealing
6.23 Vertical Drains
6.24 Vertical Wells
6.25 Water Stops
Devices provided to prevent the flow of water
through the leaks or joints.
7 TERMS RELATING TO GROUTING,
FOUNDATIONS TREATMENT AND,
7.1 Alluvium Grouting
Grouting of transported pervious media, such as.
sand, gravel and single, with clay, cement, bento-
nite andlor chemicals mixed in different propor-
7.2 Area Grouting
In cases where large zones of fractured rock, lie
at the foundation contact or where the zone of’
broken rock within a fault has great width, the
entire zone of factured rock shall be grouted to a,
shallow depth usually 3 to 1.0 m by using a grid.
pattern. This type of grouting is referred to as-
blanket grouting. It reduces leakage in the fractu-
red zone and provides a more firm foundation for
7.3 Bentonite Grouting
Grouting in which bentonite with or without other-
ingredients in the form of suspension is injected
under pressure into a pervious medium to makes
7.4 Circulating System
The piping arrangement by which grout is con-.
veyed from the grout pump to the grout hole
and through a return line from the hole to the
7.5 Chemical Grouting
Grouting in which chemicals are injected under
pressure into a pervious medium to make it water-
tight by formation of gels.
7.6 Contact Grouting
Contact grouting is a sealing operation intended.
to bring about as nearly as possible a fully boun-
ded contact between a.ny concrete structure and
the adjacent rock.
7.7 Curtain Grouting
It consists of forming an approximately vertical
grout curtain of moderate thickness below a dam
to control seepage of water.
7.8 Dental Treatment
It consists of excavating objectionable materials
from solution cavities, fault zones, seams or other
rock imperfections and filling with concrete the
cavities so excavated.
It is the disposal of surface and seepage water in
the abutments, foundation and the body of the
7.10 Foundation Drainage Holes
Holes drilled from the foundation
drainage gallery of dam into the
downstream of high pressure grout
intercept seepage through the curtain
relieve uplift pressure.
and thus to
7.11 Full Depth Grouting
A method of grouting in which the entire depth
of a hole is grouted in one operation by connecting
the grout supply line to the manifold at the top
of the hole.
A fluid or Auid mixture that can be poured or
7.13 Grout Curtain
A diaphragm or curtain in which the foundation
is made impervious by grouting process.
A process of pouring or injecting grout in the
joints, hollows, cracks, seatis, faults, shattered
zones or fracture zones, etc.
A process of laying membrane of an intimate
mixture of sand and cement pneumatically con-
veyed in a dry state to the nozzle of the cement
gun where water is added immediately prior
to expulsion and shot into place.
7.16 Internal Drainage of Dam
It usually comprises porous concrete blocks/formed
drains at the contraction joints and in the body
of the dam.
7.17 Joint Grouting
Joint grouting consists in grouting construction
joints between adjacent units of a concrete struc-
ture in order to join them together into a single
7.18 Manifold or Header
The piping arrangement at the top of the hole for
connecting the line to the hole.
7.19 Multiple Grouting
A thick grout is occasionally used during the first
stage to seal leaks; as soon as the grout in the
rock has attained a partial set the hole is washed
and redrilled then regrouted with a thinner mix.
The device used in the hole to segregate part of
a hole for grouting or percolation testing.
7.21 Packer Grouting
The use of expandable implements, such as
packers, to isolate sections of a grout hole and
thereby enable the application of grout, under
pressure only, in a portion of the hole.
Arrangement of holes in plan and vertical section.
7.23 Percolation Test
Pumping of water into a hole with or without
pressure through a direct connection or in diffe-
rent sections of hole using packers and measuring
water intake for determining permeability charac-
teristics. It is also called ‘Water Percolation Test’.
7.24 Porous Concrete Drains/Formed
These drains are provided to intercept the seepage
water and such seepage water shall ultimately be
let out into drainage gallery system. For masonry
dams, drains through porous concrete blocks are
provided and for concrete dams there shall be
7.25 Pressure Grouting
It is a process of injecting under pressure, a fluid
sealing material into the inaccessible formations
or places through specially drilled holes for the
purpose of sealing off or filling joint seams fissures
or any other openings.
7.26 Primary Holes
In split spacing grouting the first set of holes are
referred to as ‘Original Holes’ or ‘Primary Holes’.
It is the layer of large size blocks of rock or
concrete over the top surface of earth or rockfill
section of the dam to protect the underlying layer
7.28 Shear Key
A longitudinal trench in the foundation of con-
crete/masonry dam and backfilled with concrete
in order to increase the resistance against sliding.
7.29 Single Line System
The piping arrangement by which grout is con-
veyed from a grout pump to grout hole through
a single line of pipe without a return line.
7.30 Single Stage Grouting
Same as ‘Full Depth Grouting’.
IS 4410 ( Put 8 ) t 1982
7.31 Split Spacing Grouting Method
A sequence of drilling and grouting holes in which
widely spaced holes and drilled and grouted
initially and the spacing is sub-divided by inter-
mediate holes. The initial set of holes are called
primary holes and intermediate holes are termed
as secondary, tertiary, etc, according to the
sequence of subdivision.
A partial depth of holes treated or to be treated.
7.33 Stage Grouting
Grouting consisting of drilling a hole to a limited
depth or to the intersection with an open seam,
grouting to that depth, cleaning out the hole
after the grout has taken its initial set, and then
drilling and grouting the next stage. The process
is repeated, using higher pressures for each
successive stage until the final depth is reached.
Also known as ‘Down-stage Grouting’ or ‘Succes-
7.34 Subsurface Drainage
It is provided for slope protection and along
abutments so as to relieve building up of water
pressure behind the dam and the appurtenant
7.35 Successive Grouting
7.36 Surface Drainage
It is provided for all open surfaces of the dam.
Washing of the walls of the grout hole by water
under pressure after completion of drilling but
before grout injection.
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Dot: No RVD 2 ( 4334 )
Amendments Issued Since Publication
Amend No. Date of Issue Text Affected
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