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1.INTRODUCTION
A concrete dam is a solid structure, made of concrete , constructed across a river to create a
reservoir on its upstream. The section of the concrete dam is approximately triangular in shape,
with its apex at its top and maximum width at bottom. The section is so proportioned that it
resists the various forces acting on it by its own weight. Most of the gravity dams are solid, so
that no bending stress is introduced at any point. The gravity dams are usually provided with an
overflow spillway in some portion of its length. The dam thus consists of two sections; namely,
the non-overflow section and the overflow section or spillway section. The design of these two
sections is done separately because the loading conditions are different. The overflow section is
usually provided with spillway gates. The ratio of the base width to height of most of the gravity
dam is less than 1.0. The upstream face is vertical or slightly inclined. The slope of the
downstream face usually varies between 0.7: 1 to 0.8: 1.
In this research paper the concrete section of rampad sagar dam or periayr dam has taken
into consideration. The stability of the dam has determined by varying the slopes of upstream
and downstream section.
2. LITERATURE REVIEW ON ANALYSIS OF STABILITY OF DAMS:
2.1.ROMAN DAMS:
The need to store water, in particular in dry areas, was probably the main reason for the
construction of the first dams, which consisted of earth structures built in 3000 B.C., in Jawa,
present Jordan, the highest being 4m high and having a length of 80m (Figure 1a). These are
considered to be the oldest known dams. In that time romans use hyadraulic lime,earth and rock
to construct the dams. Those dams lasted for 60 to 80 years. Also around the 2nd century, the
Proserpina dam was built (Figure 1d) (H=22m, L=426m), close to Mrida. The characteristics of
the dam presents a group of nine buttresses, close to the upstream face, which support the thrust
of the downstream slope, in case the reservoir needs to be emptied. The dam maintains its
original function, which is to supply water to the city of Mrida (Jansen1980). In the 18th and
19th centuries, the economic development and a favorable legal framework for the management
of water resources led to the construction of new dams. Nevertheless, the prevailing structural
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scheme was based on trapezoidal cross-sections with a large volume, following the Roman
tradition, despite the tendency for reduction of cross sections (La 1993).
In 1971 spain scientist Sazily gave some new directions to dam design.
According to Sazilly, the cross-section of the dam should be designed so as to avoid the failure
by excessive compressive stress and by sliding. Both scenarios should be observed at the contact
between the dam and foundation, but also along the body of the dam. Also according to Sazilly,
the sliding scenario had never been observed in any previous failure, so design of the cross-
section should just take into account only the first criterion, while the sliding scenario should be
verified afterwards. In accordance with Sazillys reference, the proposed stress analysis was
based on M. Mrys work6, about the stability of arches, which was disclosed by M. Blanger in
the Cours de Mcanique Applique (Course of Applied Mechanics) delivered at Lcole
Nationale des Ponts et Chausses (National School of Bridges and Roads), France. Another
fundamental contribution was given by S. Rankine in 1872, with the publication of an article in
The Engineer, with the title Report on the design and construction of masonry dams. In this
article, Rankine confirms the validity of the former works by Sazillys and Delocres (Wegmann
1899). The sole difference consists of the use of different limit stress values for extreme load
cases. Since the limit stress is a vertical stress, the use of a lower limit stress for the downstream
face is proposed, because the larger angle with the vertical leads to a higher principal stress when
compared with the upstream face. Since no mathematical formulation was used for defining
these limits, just by taking into account the observation of existing works, Rankine suggested the
limit of 9.8kg/cm (0.96MPa), for upstream, and 7.6kg/cm (0.75MPa), for downstream (Rankine
1881).
2.2.DEVELOPMENTS IN 20th
CENTURY:
In 1905 special reference must be made to G. Wisners and E. Wheelers contributions, who, by
request of the Reclamation Service, initiated studies to better understand the load distribution on
arch dams. Global stability analysis remains an indispensable component in the safety evaluation
of gravity dams, considering the possibility of various sliding mechanisms, which place along
the foundation surface or involve rock joints (e.g. Rocha 1978). The accident of the Malpasset
arch dam in 1957 stressed the importance of the hydro-mechanical behavior of rock foundations
(Londe 1987). Knowledge on issues such as the effectiveness of the grout curtain and drainage
systems progressed with extensive field monitoring (Casagrande 1961). These data provide the
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means to validate and calibrate numerical models of seepage problems, which were already
developed in the early days (Serafim 1968). For stability analysis of gravity dams, the diagram of
uplift water pressure along the sliding surface is a decisive factor. In the absence of drainage, a
triangular or trapezoidal diagram needs to be considered . When drains are present, a reduction
of the water pressure can be considered at the drain location, leading to a bilinear diagram. It is a
common design assumption to adopt a reduction factor of 2/3 (Leclerc, Lger, and Tinawi 2003).
However, the possible development of upstream cracking may allow the full reservoir pressure
along the crack. Current design codes provide the rules for these analyses and a comparison of
criteria of three American regulatory agencies may be found in Ebeling et al. (2000), while the
practice in various countries is discussed in Ruggeri (2004)
3.TYPES OF CONCRETE DAM:
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The basic shape of a concrete gravity dam is triangular in section (Figure 1a), with the top crest
often widened to provide a roadway (Figure 1b).
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Various forces acting on the dams are shown in the below figure:-
Figure 2
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4.BASIC DEFINITIONS:
1. Axis of the dam: The axis of the gravity dam is the line of the upstream edge of the top (or
crown) of the dam. If the upstream face of the dam is vertical, the axis of the dam coincides with
the plan of the upstream edge. In plan, the axis of the dam indicates the horizontal trace of the
upstream edge of the top of the dam. The axis of the dam in plan is also called the base line of
the dam. The axis of the dam in plan is usually straight. However, in some special cases, it may
be slightly curved upstream, or it may consist of a combination of slightly curved RIGHT
portions at ends and a central ABUTMENT straight portion to take the best advantages of the
topography of the site.
2. Length of the dam: The length of the dam is the distance from one abutment to the other,
measured along the axis of the dam at the level of the top of the dam. It is the usual practice to
mark the distance from the left abutment to the right abutment. The left abutment is one which is
to the left of the person moving along with the current of water.
3. Structural height of the dam: The structural height of the dam is the difference in elevations of
the top of the dam and the lowest point in the excavated foundation. It, however, does not
include the depth of special geological features of foundations such as narrow fault zones below
the foundation. In general, the height of the dam means its structural height.
4. Maximum base width of the dam: The maximum base width of the dam is the maximum
horizontal distance between the heel and the toe of the maximum section of the dam in the
middle of the valley.
5. Toe and Heel: The toe of the dam is the downstream edge of the base, and the heel is the
upstream edge of the base. When a person moves along with water current, his toe comes first
and heel comes later.
6. Hydraulic height of the dam: The hydraulic height of the dam is equal to the difference in
elevations of the highest controlled water surface on the upstream of the dam (i. e. FRL) and the
lowest point in the river bed.
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Figure 3
5.FORCES ACTING ON GRAVITY DAM
A gravity dam is subjected to the following main forces:
1. Weight of the dam
2. Water pressure
3. Uplift pressure
4. Wave pressure
5. Earth and Silt pressure
6. Ice pressure
7. Wind pressure
8. Earthquake forces
9. Thermal loads.
These forces fall into two categories as
a) Forces, such as weight of the dam and water pressure, which are directly calculable from the
unit weights of the materials and properties of fluid pressures; and
b) Forces, such as uplift, earthquake loads, silt pressure and ice pressure, which can only be
assumed on the basis of assumption of varying degree of reliability. It is in the estimating of the
second category of the forces that special care has to be taken and reliance placed on available
data, experience, and judgment. It is convenient to compute all the forces per unit length of the
dam.
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5.1. WEIGHT OF THE DAM
The weight of the dam is the main stabilizing force in a gravity dam. The dead load to be
considered comprises the weight of the concrete or masonry or both plus the weight of such
appurtenances as piers, gates and bridges. The weight of the dam per unit length is equal to the
product of the area of cross-section of the dam and the specific weight (or unit weight) of the
material. The unit weight of concrete and masonry varies considerably depending upon the
various materials that go to make them. It is essential to make certain that the assumed unit
weight for concrete/masonry or both can be obtained with the available aggregates/ stones. The
specific weight of the concrete is usually taken as 24 kN/m3, and that of masonry as 23 kN/m3 in
preliminary designs. However, for the final design, the specific weight is determined from the
actual tests on the specimens of materials. It is essential that the actual specific weight of
concrete during the construction of the dam should not be less than that considered in the final
design. Attempts should be made to achieve the maximum possible specific weight. The factors
governing the specific weight of the concrete are water-cement ratio, compaction of concrete and
the unit weight of the aggregates. For high specific weight, the aggregates used should be heavy.
For convenience, the cross-section of the dam is divided into simple geometrical shapes, such as
rectangles and triangles, for the computation of weights. The areas and controids of these shapes
can be easily determined. Thus the weight components W1, W2, W3 etc. can be found along
with their lines of action. The total weight W of the dam acts at the C.G. of its section.
5.2. RESERVOIR AND TAILWATER LOADS (WATER PRESSURE):
The water pressure acts on the upstream and downstream faces of the dam. The water pressure
on the upstream face is the main destabilizing (or overturning) force acting on a gravity dam.
The tail water pressure helps in the stability. The tail water pressure is generally small in
comparison to the water pressure on the upstream face. Although the weight of water varies
slightly with temperature, the variation is usually ignored. In case of low overflow dams, the
dynamic effect of the velocity of approach may be significant and will deserve consideration.
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The mass of the water flowing over the top of the spillway is not considered in the analysis since
the water usually approaches spouting velocity and exerts little pressure on the spillway crest.
(Figure 4. showing various weights of dam section acting downwards)
If gates or other control features are used on the crest they are treated as part of the dam so far as
application of water pressure is concerned. The mass of water is taken as 1000 kg/m3. Linear
distribution of the static water pressure acting normal to the face of the dam is assumed. Tail-
water pressure adjusted for any retrogression should be taken at full value for non-overflow
sections and at a reduced value for overflow sections depending on the type of energy dissipation
arrangement adopted and anticipated water surface profile downstream. The full value of
corresponding tail-water should, however, be used in the case of uplift. The water pressure
intensity p (kN/m2) varies linearly with the depth of the water measured below the free surface y
(m) and is expressed as:
p=w* hwhere w is the specific weight of water (= 9.81 kN/m3 for w =1000 kg/m 3). For simplification,
the specific weight of water may be taken as 10 kN/m3
instead of 9.81 kN/m3. The water
pressure always acts normal to the surface. While computing the forces due to water pressure on
inclined surface, it is convenient to determine the components of the forces in the horizontal and
vertical directions instead of the total force on the inclined surface directly.
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(a) U/s face vertical:
When the upstream face of the dam is vertical, the water pressure diagram is triangular in shape
with a pressure intensity of wh at the base, where h is the depth of water. Th e total water
pressure Per unit length is horizontal and is given by:
It acts horizontally at a height of h/3 above the base of the dam.
(b) U/s face inclined:
When the upstream face ABC is either inclined or partly vertical and partly inclined, the force
due to water pressure can be calculated in terms of the horizontal component PH and the vertical
component PV. The horizontal component is given as earlier and acts horizontal at a height of
(h/3) above the base. The vertical component PV of water pressure per unit length is equal to the
weight of the water in the prism ABCD per unit length. For convenience, the weight of water is
found in two parts PV1 and PV2 by dividing the trapezium ABCD into a rectangle BCDE and a
triangle ABE.
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Thus the vertical component PV= PV1 + PV2 = weight of water in BCDE + weight of water in
ABE. The lines of action of PV1 and PV2 will pass through the respective centroids of the
rectangle and triangle.
5.3. UPLIFT PRESSURE:
Water has a tendency to seep through the pores and fissures of the foundation material. It also
seeps through the joints between the body of the dam and its foundation at the base, and through
the pores of the material in the body of the dam. The seeping water exerts pressure and must be
accounted for in the stability calculations. The uplift pressure is defined as the upward pressure
of water as it flows or seeps through the body of the dam or its foundation. A portion of the
weight of the dam will be supported on the upward pressure of water; hence net foundation
reaction due to vertical force will reduce. The area over which the uplift pressure acts has been a
question of investigation from the early part of this century. One school of thought recommends
that a value one-third to two-thirds of the area should be considered as effective over which the
uplift acts. The second school of thought, recommend that the effective area may be taken
approximately equal to the total area. The code of Indian Standards recommends that the total
area should be considered as effective to account for uplift.
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Figure 5
According to the Indian Standard (IS :6512-1984), there are two constituent elements in uplift
pressure: the area factor or the percentage of area on which uplift acts and the intensity factor or
the ratio which the actual intensity of uplift pressure bears to the intensity gradient extending
from head water to tail water at various points. Effective downstream drainage, whether natural
or artificial, will generally limit the uplift at the toe of the dam to tail water pressure. Formed
drains in the body of the dam and drainage holes drilled subsequent to grouting in the
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foundation, where maintained in good repair, are effective in giving a partial relief to the uplift
pressure intensities under and in the body of the dam. The degree of effectiveness of the system
will depend upon the character of the foundation and the dependability of the effective
maintenance of the drainage system. In any case, observation of the behaviour of the dam will
indicate the uplift pressures actually acting on the structure and when the lift pressure are seen to
approach or exceed design pressures, prompt remedial measures should necessarily be taken to
reduce the uplift pressures to values below the design pressures.
This following criteria are recommended by IS code for the calculating uplift forces :
(a) Uplift pressure distribution in the body of the dam shall be assumed, in case of both
preliminary and final designs, to have an intensity which at the line at the formed drains exceeds
the tailwater pressure by one-third the differential between reservoir level and tail-water level.
The pressure gradient shall then be extending linearly to heads corresponding to reservoir level
and tailwater level. The uplift shall be assumed to act over 100 percent of the area.
(b) Uplift pressure distribution at the contact plane between the dam and its foundations and
within the foundation shall be assumed for preliminary designs to have an intensity which at the
line of drains exceeds the tailwater pressure by one-third the differential between the reservoir
and tailwater heads. The pressure gradient shall then be extended linearly to heads corresponding
to reservoir level and tailwater level. The uplift shall be assumed to act over 100 % area. For
final designs, the uplift criteria in case of dams founded on compact and unfissured rock shall be
as specified above. In case of highly jointed and broken foundation, however, the pressure
distribution may be required to be based on electrical analogy or other methods of analysis
taking into consideration the foundation condition after the treatment proposed. The uplift shall
be assumed to act over 100 % of the area.
5.4. EARTH AND SILT PRESSURES:
Gravity dams are subjected to earth pressures on the downstream and upstream faces where the
foundation trench is to he backfilled. Except in the abutment sections in specific cases and in the
junctions of the dam with an earth or rockfill embankment, earth pressures have usually a minor
effect on the stability of the structure and may be ignored. The present procedure is to treat silt as
a saturated cohesionless soil having full uplift and whose value of internal friction is not
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materially changed on account of submergence. Experiments indicate that silt pressure and water
pressure exist together in a submerged fill and that the silt pressure on the dam is reduced in the
proportion that the weight of the fill is reduced by submergence. IS code recommends that a)
Horizontal silt and water pressure is assumed to be equivalent to that of a fluid with a mass of
1360 kg/m3, and b) Vertical silt and water pressure is determined as if silt and water together
have a density of 1925 kg/m3.
Figure 6
5.5. ICE PRESSURE:
The problem of ice pressure in the design of dam is not encountered in India except, perhaps, in a
few localities. Ice expands and contracts with changes in temperature. In a reservoir completely
frozen over, a drop in the air temperature or in the level of the reservoir water may cause the
opening up of cracks which subsequently fill with water and freezed solid. When the next rise in
temperature occurs, the ice expands and, if restrained, it exerts pressure on the dam. In some
cases the ice exerts pressure on the dam when the water level rises. For ice sheets of wide extent
this pressure is moderate but in smaller ice sheets the pressure may be of the same order of
magnitude as in the case of extreme temperature variation. Ice is plastic and flows under
sustained pressure. The duration of rise in temperature is, therefore, as important as the
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magnitude of the rise in temperature in the determination of the pressure exerted by ice on the
dam. Wind drag also contributes to the pressure exerted by ice to some extent. Wind drag is
dependent on the size and shape of the exposed area, the roughness of the surface area and the
direction of wind. Existing design information on ice pressure is inadequate and somewhat
approximate. Good analytical procedures exist for computing ice pressures, but the accuracy of
results is dependent upon certain physical data which have not
been adequately determined. These data should come from field and laboratory. Till specific
reliable procedures become available for the assessment of ice pressure it may be provided for at
the rate of 250 kPa applied to the face of dam over the anticipated area of contact of ice with the
face of dam.
5.6. WIND PRESSURE
Wind pressure does exist but is seldom a significant factor in the design of a dam. Wind loads
may, therefore, be ignored.
5.7. WAVE PRESSURE
In addition to the static water loads the upper portions of dams are subject to the impact of
waves. Wave pressure against massive dams of appreciable height is usually of little
consequence. The force and dimensions of waves depend mainly on the extent and configuration
of the water surface, the velocity of wind and the depth of reservoir water. The height of wave is
generally more important in the determination of the free board requirements of dams to prevent
overtopping by wave splash. An empirical method based upon research studies on specific cases
has been recommended by T. Saville for computation of wave height hw (m). It takes into
account the effect of the shape of reservoir and also wind velocity over water surface rather than
on land by applying necessary correction. It gives the value of different wave heights and the
percentage of waves exceeding these heights so that design wave height for required exceedance
can be selected. Wind velocity of 120 km/h over water in case of normal pool condition and of
80 km/h over water in case of maximum reservoir condition should generally be assumed for
calculation of wave height if meteorological data is not available. When maximum wind velocity
is known, the same shall be used for full reservoir level (FRL) condition and 2/3 times that for
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MWL condition. The maximum unit pressure pw in kPa occurs at 0.125 hw, above the still water
level and is given by the equation:
Pw=24 hw
The total wave force Pw, (in kN) is given by the area of the triangle 1-2-3
Pw=20
Figure 7
5.8. EARTHQUAKE FORCES
The earthquake sets up primary, secondary, Raleigh and Love waves in the earth's crust. The
waves impart accelerations to the foundations under the dam and. causes its movement. In order
to avoid rupture, the dam must also move along with it. This acceleration introduces an inertia
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force in the body of dam and sets up stresses initially in lower layers and gradually in the whole
body of the dam. Earthquakes cause random motion of ground which can be resolved in any
three mutually perpendicular directions. This motion causes the structure to vibrate. The
vibration intensity of ground expected at any location depends upon the magnitude of
earthquake, the depth of focus, distance from the epicentre and the strata on which the structure
stands. The predominant direction of vibration is horizontal. The response of the structure to the
ground vibration is a function of the nature of foundation soil; materials, form, size and mode of
construction of the structure; and the duration and the intensity of ground motion. IS:1893 - 1984
code specifies design seismic coefficient for structures standing on soils or rocks which will not
settle or slide due to loss of strength during vibrations. The seismic coefficients recommended in
this standard are based on design practice conventionally followed and performance of structures
in past earthquakes. In the case of structures designed for horizontal seismic force only, it shall
be considered to act in any one direction at a time. The vertical seismic coefficient shall be
considered in the case of structures in which stability is a criterion of design. For the purpose of
determining the seismic forces, the country is classified into five zones.
6.RAMPAD SAGAR DAM ON POLAVARAM PROJECT:
Godavari is the largest river in South India, it starts at Nasik in the western ghats and runs South
East area is about 1.2 lakh sq.miles, greater than the area of Britan. Its annual average flow is
3600 Thousand Million Cubic ft. (TMC ) (83 MA ft.). But its highest yield is 5,860 TMC and the
lowest in 65 years is 960 TMC. Its peak flood flow is more than 20 lakh cusecs. Godavari water
is used by construction of an anicut near Rajahmundry during 1850-60 by Sir Arthur Cotton. The
second crop depends upon low summer flows and hence higher food production required new
irrigation projects and hence Rampada Sagar was conceived during the British rule to augment
irrigation land. This project consists of a 428 ft. height dam , 20 miles upstream of Rajahmundry
and 1.5 miles above Polavaram with two major canals, one extending on the left upto
Visakhapatnam and the other on the right extending upto Gundlakamma river with a hydro
power of 150 MW on the right bank.
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( Figure 8 Delta section of Godavari river)
The dam is 6600ft. long and 428 ft. high from deepest foundation. FRL of the Reservoir
is +198ft, with a water spread of 527 sq.miles with a gross storage of 690 TMC. Crest level of
drum is +180ft. road level 237.82, Tail water is at +43ft. Foundation bed level rock is between
bed width at foundation is 303 ft. under spillway section. To dispose of the maximum floods the
spill way is 4,200 ft. long with 16 drum gates of 135ft. x 18ft. There will be 100 sluices of 10ft. x
20ft with silt at +83 ft. to dispose of silt- laden floods. The river flow from the middle of June to
middle of September will be diverted into the canals and the sand sluices will dispose of the
floods at the diversion level of +145. The annual silt deposition is estimated at 2 TMC in the
initial stages and 0.33 TMC during the later periods and hence the silt capacity is provided for168 TMC for a life of 400years for the reservoir.
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(Figure 9 View of rampad sagar dam)
7.SEISMIC RISKS TO POLAVARAM DAM
Risks due to location in a highly earthquake prone rift zone of Bhadrachalam:
Polavaram dam and its reservoir are located close to highly earthquake prone areas like
Bhadrachalam which has been rated seismically as one of the 10 dangerous rift zones and it has
faced hazardous earthquakes for some time. Koyna reservoir located under similar earthquake
danger zone has experienced major earthquakes due to Reservoir Induced Seismicity [RIS] and
experienced cracks in the dam resulting in serious damage in 1967. The higher the height of the
dam, greater will be the damage due to earthquakes in the rift zones
The Godavari river valley is within the NW-SE trending faults. These faults still show moderate
seismicity occasionally. The Godavari graben area is in seismic Zone III of the seismic zoning
map of Bureau of Indian Standard. In this zone an earthquake of magnitude 6 or intensity VIII
may be expected. The earthquake of magnitude 5.7 was measured at Bhadrachalam in 1969. In
terms of the risks of an earthquake with damage potential, the most active zones in A.P State
are the Eastern Ghat belt and the Godavari valley. The minor risk areas are Hyderabad,
Vinukonda-Ongole, Chittoor and Vizianagaram . Since 1800, a total of 80 earthquakes of
magnitude 3.5 to 5.7 have struck different parts of the Andhra Pradesh State. The strongest of
them was the April 1969 Bhadrachalam earthquake, which measured 5.7 on the Richter scale.
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The earthquakes are known to be triggered by reservoir loading in area of moderate seismicity.
However, magnitude of the triggered earthquake, is not anticipated to exceed the magnitude of
the largest earthquake expected in the area. In the present case, earthquake may be triggered after
reservoir loading and the largest expected earthquake in the area will be in the magnitude of 6. If
this magnitude exceeds, then the peak ground accelerations may cause damage to the dams
( Figure 10 section view of rampad sagar dam)
During 1850s Sir Arthor Cotton suggested for a barrage at Polavaram:
Sir Arthor Cotton was a great humanist and a friend of the farmers wanted maximum utilization
of Godavari waters for augmenting agriculture and suggested that in order to irrigate the uplands
of East and West Godavari districts. Another anicut must be constructed on the upstream side of
Rajahmundry. Because he was a great Irrigation Engineer with humanistic outlook and great
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vision he knew that it will be a highly dangerous to propose a major water storage dam in the
close proximity of growing townships like Rajahmundry which may be adversely affected due to
collapse of such a major storage dam for one reason or the other. Hence Sir Arthor Cotton
suggested for an anicut to irrigate more lands in the upland areas of Eastern ghats in East
Godavari and West Godavari districts.
In 1945, Madras Government proposed a high concrete dam at Polavaram site : Madras
Presidency Government proposed a major reservoir project across Godavari before independence
and it was known as Ramapada Sagar project with a height of 198ft. in the first phase to raised to
208ft. in the final phase with a storage capacity of 690 TMC. This was proposed as a concrete
dam with a total height of 438ft. upto the foundations with sand bed extending for a depth of
about 230ft. below the bed level. The spillway was provided for a length of 4200ft for a peak
discharge of 21 lakh cusecs. Since concrete dam had to be taken upto the bedrock for its safety
the cost of the project became too high and hence the high cost factor made the dam not all
feasible and hence it was given up.
In 1953 Khosla Technical Committee suggested for a Barrage at Polavaram site: The
Government of India appointed a high power technological committee under the chairmanship of
Dr.A.N.Khosla, Chairman of the Central Water Commission (CWC) to study and submit report
on the optimal utilization of water in Krishna-Godavari and Pennar rivers. This committee stated
that there is a possibility of diverting Godavari water by constructing either a dam or a diversion
barrage with a canal to transfer 142 TMC into Krishna river. The Committee further stated that if
Ramapad Sagar dam is not built but a storage reservoir is constructed upstream on Godavari or
its tributaries and only a diversion barrage is built at Ramapadsagar dam site the transfer of 142
TMC of water into Krishna river will remain unaffected.
In 1961 AP State Government Suggested for a Barrage at Polavaram site: In a technical report by
the AP State Government prepared a 1961 on the optimum economic utilization of Krishna and
Godavari waters the state Government recommended for construction of a barrage at Rampad
Sagar site and a dam at Inchampalli to divert Godavari waters into Krishna rivers in Para 23 of
the Report in the following words.
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The only practical scheme for diversion of Godavari waters to Krishna basin the lower reaches
is by construction of Inchampalli dam and Rampad Sagar barrage. By this it will be possible to
divert waters at less cost than the previous proposals (made by Maharashtra state Government) as
the tunnels are eliminated and length of the canal reduced. But this itself is very costly as
commented upon by the technical committee (Khosla committee) who stated that with a small
quantity of water for diversion the economics of the proposal becomes problematic.
In 1962 the Technical Committee headed by Gulhati suggested for a barrage at Polavaram site:
The Ministry of Irrigation and Power, Government of India appointed in a technical commission
in May 1961 to study and submit a report on the utilization of Krishna and Godavari waters
including the feasibility of diverting Godavari waters into Krishna river and the committee
submitted its report in August 1962. This Commission was headed by an eminent engineer
Mr.Gulhati along with other highly technically qualified experts as members. The Commission
in its report stated that there will be ample surplus water in the upper part of the Godavari basin
to meet the demands of thelocal projects and the surplus water from the lower part of the
Godavari basin including the sub basins of Pranahita, Indravati and Sabari can be used for
irrigation and hydro-power projects will be more than 10 MAF (435 TMC) and this surplus flow
can be diverted into Krishna basin by the following 2 link canals.
1. A link canal from the Godavari from the anicut at Albaka (or Singareddi) to Pulichintala on
the Krishna river, estimated at Rs.40 crores. This link canal can transfer about 95 TMC (2.2
MAF) to the Krishna.
2. A link canal from Godavari near Polavaram can transfer about 211 TMC (4.8 MAF) into
Krishna river at Vijayawada estimated at Rs.40 crores about 30 TMC from Penganaga can be
transferred through a link canal to make up the shortage of water in the Upper Godavari area.
In 1965 a technical Committee headed by Mr.A.C. Mitra suggested a barrage at Polavaram site:
The Government of India appointed an expert committee in the wake of recurring floods in
Godavari and Krishna rivers which were causing excessive flooding of the Kolleru lake to study
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the impacts of floods and suggest remedial measures. This technical committee headed by an
eminent irrigation expert Mr.A.C.Mitra along with other irrigation experts recommended for the
construction of a barrage at Polavaram for irrigating the upland areas on either side of the
barrage.
Rampad Sagar Reservoir is so named for the reason that the waters of the reservoir will lap the
feet of Srirama at the Bhadrachalam temple, 74 miles above the proposed dam near Polavaram
village. This Concrete Dam was intended to irrigate 24 lakhs of acres with Paddy cultivation in
addition to stabilizing irrigation in 21 lakh acres in Godavari and Krishna delta and will yield a
million tonnes of rice that will eliminate all the pre-war imports of rice from Burma and
Travancore. Hydro-power of 75000KV and the projected was expected to be completed by the
end of 1946. Project cost was Rs.63 crores. The net return is 3.7% per annum on the net capital
outlay. Rock was below 200 ft. and it proved uneconomical and posed difficulties and was given
up.
In 1970 AP State Engineers proposed a big reservoir at Polavaram but designated it as a barrage
: AP State submitted Polavaram barrage scheme in June 1970 to the Bachawat Tribunal. This
scheme consists of a barrage across Godavari at Polavaram with FRL at +145ft. and minimum
pond level at +45ft with Left Bank Canal upto Vizag Port with Full Supply Level with (FSL) at
+137ft and Right Canal upto Krishna river with FSLat +138ft. Safe Concrete Dam was replaced
by a risky Earth-cum-rock fill dam
In 1978 AP State Engineers proposed a hazardous earth-cum-rockfill dam at Polavaram site:
AP state changed the Polavaram barrage scheme into an earth-cum-rockfill dam with a
maximum height of 48.77m (160ft) with a crest length of 1555m (5100ft) . It had 2 spillways on
the right flank sadal with 50 radial gates (50ft. x 42ft) with a flood lift of a 14ft. for peak design
flood of 36 lakh cusecs. It had a concrete gravity dam on the left flank with Power house and
river sluices. The earth dam is 35.05m (115ft) above the average river bed and 48.77m (160ft)
above the deepest bed level of the river. This height for the dam is stated to be necessary for
diverting the required quantity of water into the canals which proposed to irrigate vast areas on
both the flanks. The MDDL and FRL stated to be required are +44.2m (145ft.) and RL +47.72m
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(+150ft) respectively with gross storage capacity of 5665 Mm3 (192 TMC) The storage available
between the minimum draw down level and FRL (44.20m to 45.72) is only 800 Mm3 (28.31
TMC). The project serves 4.82 lakh ha. (11.90 lakh acres) of Ayacut during Kharif (June to
October) and 2.27 lakh ha (5.6 lakh acres) under second crop (Jan to April) in the ultimate stage.
The left canal, 208kmlong upto Visakhapatnam and it serves industrial needs and irrigates 1.89
lakh ha under first crop and 1.25 lakh ha. under second crop in East Godavari and
Visakhapatnam. A lift irrigation canal starts at Km 177 near Anakapalli, 130km long irrigates
1.15lakh ha in Visakhapatnam and Srikakulam. Another lift canal, 177km long starts at
Polavaram to serve upland areas of 0.57 lakh ha under first crop and 0.2 lakh ha under second
crop in East Godavari and Visakhapatnam districts. The right main gravity canal 176km long
upto Budameru river irrigates 1.21 lakh ha. under first crop and 0.80 lakh ha. under second crop
in West Godavari and Krishna districts.
In August, 1978 AP State made a conditional Agreement with Karnataka on Polavaram dam: On
4-8-1978 an agreement was signed between Karnataka and AP State under which clause-VII
states that under the condition that clearance to Polavaram project is given by CWC for
FRL/MWL of +150ft. MSL. AP State agrees to divert 80 TMC into Krishna for utilization by
projects upstream of Nagarjuna Sagar by allotting share of 45 TMC to AP State and 35 TMC to
both Karnataka and Maharashtra. Another condition is that AP Sate submits Polavaram project to
CWC within 3 months of striking an agreement with all the 5 river basin states and that AP state
will bear the full cost of this water diversion and if this quantity diverted is exceeded the water
will be shared in the above stated proportion. Surprisingly while the Karnataka state Government
which has no adverse impacts due to Polavaram project has taken the initiative to fix the height
of the Polavaram dam the most effected states of Madhya Pradesh and Orissa were left with the
option of deciding to agree on the crucial matter on submersion of lands in their states. Andhra
Pradesh made agreements with Madhya Pradesh on 7-8-1978 and Orissa on 15-12-1978 on the
issue of submersion of lands due to Polavaram project with the condition that including
backwater effect. The design of the Polavaram project should be such that the submersion should
not exceed +150ft MSL at Konta in Madhya Pradesh and Motu in Orissa due to maximum
Probable Flood and backwater effects determination in consultation with Central Water
Commission.
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July, 1979: CWC finds fault with AP State for a faulty agreement on Polavaram: The CWC sent
letter No.6/125/78-T.E/25 12-2514, dated the 3rd July, 1979 to Andhra Pradesh Government, the
material portion of which is as follows:-
It is seen from the project report that the State Government of Andhra Pradesh have proposed
the Polavaram project for an FRL/MWL of +150ft. Therefore, prima facie, with MWL at
Polavaram at RL +150ft. submergence due to all effects including that of backwater effect will
always be more than RL+150ft upstream and also at Konta. The State Government will no doubt
be working out the backwater effects at Konta/Motu considering advance releases from
polavaram dam. It is however seen that during the year 1966 CWC had observed that a flood
level at Konta had reached an RL 46.595m (RL 152.88ft) which is 0.875m higher than RL
45.72m (RL+150ft) This is an observed flood whose frequency is expected to be high. For a
flood at Konta corresponding to frequency the flood adopted for the Polavaram dam (which will
be between 1 in 500 years to 1 in 1000 years), the natural flood level at Konta should be
expected to be substantially higher than RL +45.72m (RL +150ft) It would thus be seen that the
stipulation that a flood level at Konta/Motu should not rise above RL +150ft will not be
practicable and that the agreements entered into by the states may have to be suitably modified.
Perhaps this situation about observed flood level at Konta might not have been known to you and
other states when this agreement was concluded.
In October 1979 Maharashtra supports the conditional agreement on Polavaram dam: On 15-
10-79 the Maharashtra state Government took a very cantankerous cold blooded and brutal stand
on the Polavaram dam project by demanding the Bachawat Tribunal to consider the agreement of
4th August 1978 between AP state and Karnataka as a practicable one and to consider the
temporary submergence in Orissa and Madhya Pradesh preventable by constructing and
maintaining protective embankment in the interests of Justice and for securing most equitable
allocation of waters in the Godavari river. Consequently Maharashtra wanted the tribunal to
incorporate and give effect to clause VII in Karnataka Government in its report under Sec 5(2)
and pass the required order and thereby implying that the tribunal must permit for the
construction of Polavaram dam with FRL at +150ft irrespective of any disastrous consequences
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and at any cost. Madhya Pradesh disagrees with the contention of Maharashtra:
This Maharashtra petition was circulated to other basin states for replies. Karnataka did not file
any reply. Andhra Pradesh submitted the tabulated statement of backwater level for the pre and
post project conditions for 30 lakhs and 36 lakhs cusecs flood. AP wanted FRL 150subject to the
safeguards regarding flood protection works. Madhya Pradesh disagreed with views of
Maharashtra.
Orissa insists on integrated water resources planning for projects at Inchampalli and Polavaram:
Orissa stated that Polavaram and Inchampalli projects are closely interlinked because Polavaram
project is dependent on the releases from Inchampalli Hydro-Power plant and the FRL and MWL
of Polavaram depend upon the FRL and MWL of Inchampalli project and its spillway discharge
capacity and the pattern of releases from Inchampalli and both these projects would be so
palnned that the submergence in Madhya Pradesh and Orissa would not exceed +150ft due to all
causes. Orissa rejected the arguments of Maharashtra on Polavaram project while Karanakata
though did not file a reply yet it tried to support the arguments of Maharashtra.
The raise in elevation of the surface profile of a river when the flow is retarder above a dam is
referred to as the backwater effect of the dam. It is the excess submergence over and above that
by natural floods as caused by the backwater effects due to the Polavaram dam that is to be
avoided or minimized as far as possible. But the correct backwater effect or backwater level due
to Polavaram dam must be determined by the CWC as per para 110 of the Bachawat Tribunal
report.
The tribunal under chapter-2 of the final report dt.7-7-1980 under sec 5 (3) and Paragraph 12 the
tribunal left the matter for the clearance of the Polavaram project to the CWC after making the
following observations
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The CWC will naturally keep all these points in view while clearing the Polavaram project in
consultation with the concerned parties, after giving due consideration to achieve the objectives
mentioned in the project reports of Andhra Pradesh. The tribunal however, on its part does not
find any difficulty for clearing the Polavaram project at FRL/MWL +150ft.
AP State Proposes Embankments to Prevent submersion in Upper States and insists on
conditions:
On 26-10-1979 AP state agreed to prevent temporary submersion due to the dam by constructing
and maintaining protective embankments. The AP also stated that there can be no question of
diversion of Godavari waters into Krishna unless Polavaram project is cleared for FRL +150ft
and subject to such safeguards as the tribunal may provide so as to give effect to all the
agreements without detriment to any of the parties (Para 123 of the Tribunal report)
1980: During the President rule in Orissa, a middle level engineer was deputed on behalf of
Orissa state government to sign on agreement along with AP and Madhya Pradesh and Central
government on Polavaram project. The Government of India gave in writing on 26-3-1980 that
Polavaram dam with FRL at +150ft. is technically feasible. But Environmental safety was
ignored
In the final submissions before the Bachawat Tribunal the AP State Government demanded on
25-2-1980 the tribunal that since both the upper states have agreed for permanent submersion of
their lands upto +150ft the tribunal may permit submersion of lands in Orissa and Madhya
Pradesh upto 175ft but it is not accepted because submersion had to be prevented by construction
of embankments as suggested by the Central Water Commission with adequate pumping
arrangements and drainage sluices. Thus the interstate agreement envisaged that AP state will
submit proposals for Polavaram dam within 3 months of the agreement made by all the 5 river
basin states so that the CWC will clear the project as expeditiously as possible to enable the state
Government to complete the project in time .Because of the Delay of the project by 25 years, all
the legal and environmental hurdles have cropped up such as increase of peak floods from 36 to
50 lakhs cusecs and the consequential increase in submersion levels in upper states, making
Bachawat Award conditions invalid. In fact, the villages likely to be submerged rose from 275
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estimated in 1980 to 340 by 2010.This additional submersion of lands and villages is not
acceptable to the Orissa and chattisgarh states and it amounts to violation of conditions of the
Bachawat Tribuna of April.1980.
30-4-1983: Dr.K.L.Rao warned that Polavaram dam is under-designed and is unworkable. He
expressed strong opposition to the Dam because of various reasons like under-designed spillway
for the higher levels of peak floods expected to occur in the near future.
1985 : Detailed project report [DPR]of Polavaram project completed
1987 : Project Report [DPR]submitted to the CWC
1996 : R&R reports prepared through Centre for Evaluation of Socio-Economic Studies.These
study reports were never updated on the basis of upgrading peak flood from 36 lakhs cusecs in
1980 to50 lakhs cusecs in 2006 by A.P.state Engineers and also the Central water Commission
without the consent of Orissa and Chattisgarh states as per the conditions of the Bachawat
tribunal Award
1996 :Dr.K.Sriramakrishnayya, irrigation Advisor to A.P.state Government strongly opposed
polavaram dam for several reasons and suggested that it should be left to be decided by the
future generations]for details see his report presented in brief elsewhere under these web sites on
polavaram dam]
June, 1999: Dam Break Analysis report for Polavaram by National Institute of Hydrology,
Roorkee, a wing of Union Ministry of Water Resources at the request of the Environmental
Protection Training and Research Institution (EPTRI) of the AP State Government which was
interested with the preparation of environmental impact assessment report for Polavaram dam
project.
2002 : EIA-EMP reports prepared by the Environment Protection Training &Research
Institute[EPTRI],Hyderabad are incomplete as they were based on old and incomplete data of
1996
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16-09-2005 : The AP State Government was in a great hurry to start construction work on
Polavaram dam and since EPTRI was a professionally qualified organization it wanted sufficient
time to prepare the EIA report by conducting fresh field studies to upgrade the project report .But
the irrigation Secretaries were impatient and they wanted to somehow get a routine report on
EIA done by other agencies who were willing to prepare the project in a shorter time for the
routine purpose of submitting the project to the Union Ministry of Environment to secure the
Environmental clearance within the shortest possible time.
Naturally the EIA-EMP partly prepared by EPTRI was handed over to M/s AFC Ltd.
Hyderabad for updating the same and this organization did not have sufficient number of experts
in the different fields of ecology, hydrology and environmental sciences and engineering as
experts who could be considered qualified as envisaged by article 45 of the Evidence Act. The
relevant reports were not prepared in a comprehensive manner as per rules and regulations and
without proper assessment of the dam break analysis report, risk analysis report, disaster
management report and Environmental Management report including the different alternatives
thoroughly analyzed for the Polavaram dam project . Hence such incomplete reporters were
submitted by the AP State Government to the Union Ministry of Environment for obtaining
environmental clearance in a great hurry.
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8.CALCULATION OF FACTOR OF SAFETY BY VARYING DOWNSTREAM SLOPE
OF RAMPADSAGAR DAM
8.1. FOR 7/10 DOWNSTREAM SLOPE
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FORCE NAME MAGNITUDE (KN) LEVER ARM
(M)
MOMENT DUE TO FORCRE
AT TOE (KNM)
WEIGHT DUE TO TRIANGULAR
PORTION W1
X57.58 X82.2 X23.5 X 1=
55654.23
38.38 +2136009.347
WEIGHT DUE TO RECTANGULAR
PORTIONW2
96.87X 8.33X
23.5X1=18962.78
61.745 +1170857.27
WEIGHT OF WATER SUPPORTED
ON DOWNSTREAM W3
X26.24X37.49X1X
9.81=4825.23
8.746 +42201.46
UPLIFT U1 522.26 X 6.061 62.879 -199038.30
UPLIFT U2 X308.90 X6.061 63.889 -59823.35
UPLIFT U3 367.77X 59.849 29.92 -658559.14
UPLIFT U4 X59.849 X154.49 39.89 -184412.90
WATER PRESSURE ON UPSTREAM
FACE
X 84.73 X831.24 28.24 -994532.03
WATER PRESSURE ON
DOWNSTREAM FACE
X367.77 X37.49 12.496 +86145.52
EARTH QUAKE FORCE, VERTICAL
(UPWARD)
0.05 X 74617.01=
-3730.85
0.05 X 3306866.617=
-165343.33
HORIZONTAL EARTHQUAKE ,
WORST CASE TOWARDS
DOWNSTREAM, PW1,DUE TO
TRIANGULAR PORTION
0.1 X 55654.23 =
- 5565. 423
27.4 -152492.59
PW2,DUE TO
RECTANGULAR PORTION
0.1 X 18962.78= 1896.278 48.43 -91836.74
HYDRODYNAMIC FORCE , Pe .555 X 0.1 X 84.73 X 9.81= 4H/3 =
(4 X
84.73)/3
=35.96
-1658.85
WAVE FORCE ,Pw Hw= 0.032 X(V.F)1/2
+0.763-0.271 (F)3/4
TAKING V=40 KMPH
AND FETCH=5KM
Hw=0.309 M
19.62 X.3092=1.873
3/8
X.309+84.73
-158.91
M+VE/MVE =1.369 APPROX= 1.37
M +VE = MVE=
+2136009.34 -199038.30
+1170857.27 -59823.35
+42201.46 -658559.14
+86145.52 -184412.90
-994532.03
-165343.33
-152492.59
-91836.74
-1658.85
-158.91
=+3435214 =-2507856
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8.2. FOR 8/10 DOWNSTREAM SLOPE
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FORCE NAME MAGNITUDE (KN) LEVER ARM
(M)
MOMENT DUE TO FORCRE
AT TOE (KNM)
WEIGHT DUE TO TRIANGULAR
PORTION W1
WEIGHT DUE TO RECTANGULAR
PORTIONW2
WEIGHT OF WATER SUPPORTED
ON DOWNSTREAM W3
UPLIFT U1
UPLIFT U2
UPLIFT U3
UPLIFT U4
WATER PRESSURE ON UPSTREAM
FACE
WATER PRESSURE ON
DOWNSTREAM FACE
EARTH QUAKE FORCE, VERTICAL
(UPWARD)
HORIZONTAL EARTHQUAKE ,
WORST CASE TOWARDS
DOWNSTREAM, PW1,DUE TO
TRIANGULAR PORTION
PW2,DUE TO
RECTANGULAR PORTION
HYDRODYNAMIC FORCE , Pe
WAVE FORCE ,Pw
M+VE/MVE =
M +VE = MVE=
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8.3.FOR 6/10 DOWNSTREAM SLOPE
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FORCE NAME MAGNITUDE (KN) LEVER ARM
(M)
MOMENT DUE TO FORCRE
AT TOE (KNM)
WEIGHT DUE TO TRIANGULAR
PORTION W1
WEIGHT DUE TO RECTANGULAR
PORTIONW2
WEIGHT OF WATER SUPPORTED
ON DOWNSTREAM W3
UPLIFT U1
UPLIFT U2
UPLIFT U3
UPLIFT U4
WATER PRESSURE ON UPSTREAM
FACE
WATER PRESSURE ON
DOWNSTREAM FACE
EARTH QUAKE FORCE, VERTICAL
(UPWARD)
HORIZONTAL EARTHQUAKE ,
WORST CASE TOWARDS
DOWNSTREAM, PW1,DUE TO
TRIANGULAR PORTION
PW2,DUE TO
RECTANGULAR PORTION
HYDRODYNAMIC FORCE , Pe
WAVE FORCE ,Pw
M+VE/MVE =
M +VE = MVE=
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8.4 .FOR 5/10 DOWNSTREAM SLOPE
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FORCE NAME MAGNITUDE (KN) LEVER ARM
(M)
MOMENT DUE TO FORCRE
AT TOE (KNM)
WEIGHT DUE TO TRIANGULAR
PORTION W1
WEIGHT DUE TO RECTANGULAR
PORTIONW2
WEIGHT OF WATER SUPPORTED
ON DOWNSTREAM W3
UPLIFT U1
UPLIFT U2
UPLIFT U3
UPLIFT U4
WATER PRESSURE ON UPSTREAM
FACE
WATER PRESSURE ON
DOWNSTREAM FACE
EARTH QUAKE FORCE, VERTICAL
(UPWARD)
HORIZONTAL EARTHQUAKE ,
WORST CASE TOWARDS
DOWNSTREAM, PW1,DUE TO
TRIANGULAR PORTION
PW2,DUE TO
RECTANGULAR PORTION
HYDRODYNAMIC FORCE , Pe
WAVE FORCE ,Pw
M+VE/MVE =
M +VE = MVE=
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8.5 .FOR 9/10 DOWNSTREAM SLOPE
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FORCE NAME MAGNITUDE (KN) LEVER ARM
(M)
MOMENT DUE TO FORCRE
AT TOE (KNM)
WEIGHT DUE TO TRIANGULAR
PORTION W1
WEIGHT DUE TO RECTANGULAR
PORTIONW2
WEIGHT OF WATER SUPPORTED
ON DOWNSTREAM W3
UPLIFT U1
UPLIFT U2
UPLIFT U3
UPLIFT U4
WATER PRESSURE ON UPSTREAM
FACE
WATER PRESSURE ON
DOWNSTREAM FACE
EARTH QUAKE FORCE, VERTICAL
(UPWARD)
HORIZONTAL EARTHQUAKE ,
WORST CASE TOWARDS
DOWNSTREAM, PW1,DUE TO
TRIANGULAR PORTION
PW2,DUE TO
RECTANGULAR PORTION
HYDRODYNAMIC FORCE , Pe
WAVE FORCE ,Pw
M+VE/MVE =
M +VE = MVE=
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9.CALCULATION OF FACTOR OF SAFETY BY VARYING UPSTREAM SLOPES
9.1 .FOR 2/10 UPSTREAM SLOPE
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FORCE NAME MAGNITUDE (KN) LEVER ARM
(M)
MOMENT DUE TO FORCRE
AT TOE (KNM)
WEIGHT DUE TO TRIANGULAR
PORTION W1
WEIGHT DUE TO RECTANGULAR
PORTIONW2
WEIGHT OF SMALL TRIANGULAR
PORTION ON UPSTREAM W3
WEIGHT OF WATER SUPPORTED
ON DOWNSTREAM W4
WEIGHT OF WATER SUPPORTED
ON UPSTREAM(RECTANGLE) W5
WEIGHT OF WATER SUPPORTED
ON UPSTREAM(TRIANGLE) W6
UPLIFT U1
UPLIFT U2
UPLIFT U3
UPLIFT U4
WATER PRESSURE ON UPSTREAM
FACE
WATER PRESSURE ON
DOWNSTREAM FACE
EARTH QUAKE FORCE, VERTICAL
(UPWARD)
HORIZONTAL EARTHQUAKE ,
WORST CASE TOWARDS
DOWNSTREAM, PW1,DUE TO
TRIANGULAR PORTION
PW2,DUE TO
RECTANGULAR PORTION
PW3,DUE TO SMALL TRIANGULAR
PORTION ON UPSTREAM
HYDRODYNAMIC FORCE , Pe
WAVE FORCE ,Pw
M+VE/MVE =
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9.2 .FOR 3/10 UPSTREAM SLOPE
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FORCE NAME MAGNITUDE (KN) LEVER ARM
(M)
MOMENT DUE TO FORCRE
AT TOE (KNM)
WEIGHT DUE TO TRIANGULAR
PORTION W1
WEIGHT DUE TO RECTANGULAR
PORTIONW2
WEIGHT OF SMALL TRIANGULAR
PORTION ON UPSTREAM W3
WEIGHT OF WATER SUPPORTED
ON DOWNSTREAM W4
WEIGHT OF WATER SUPPORTED
ON UPSTREAM(RECTANGLE) W5
WEIGHT OF WATER SUPPORTED
ON UPSTREAM(TRIANGLE) W6
UPLIFT U1
UPLIFT U2
UPLIFT U3
UPLIFT U4
WATER PRESSURE ON UPSTREAM
FACE
WATER PRESSURE ON
DOWNSTREAM FACE
EARTH QUAKE FORCE, VERTICAL
(UPWARD)
HORIZONTAL EARTHQUAKE ,
WORST CASE TOWARDS
DOWNSTREAM, PW1,DUE TO
TRIANGULAR PORTION
PW2,DUE TO
RECTANGULAR PORTION
PW3,DUE TO SMALL TRIANGULAR
PORTION ON UPSTREAM
HYDRODYNAMIC FORCE , Pe
WAVE FORCE ,Pw
M+VE/MVE =
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9.3 .FOR 4/10 UPSTREAM SLOPE
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FORCE NAME MAGNITUDE (KN) LEVER ARM
(M)
MOMENT DUE TO FORCRE
AT TOE (KNM)
WEIGHT DUE TO TRIANGULAR
PORTION W1
WEIGHT DUE TO RECTANGULAR
PORTIONW2
WEIGHT OF SMALL TRIANGULAR
PORTION ON UPSTREAM W3
WEIGHT OF WATER SUPPORTED
ON DOWNSTREAM W4
WEIGHT OF WATER SUPPORTED
ON UPSTREAM(RECTANGLE) W5
WEIGHT OF WATER SUPPORTED
ON UPSTREAM(TRIANGLE) W6
UPLIFT U1
UPLIFT U2
UPLIFT U3
UPLIFT U4
WATER PRESSURE ON UPSTREAM
FACE
WATER PRESSURE ON
DOWNSTREAM FACE
EARTH QUAKE FORCE, VERTICAL
(UPWARD)
HORIZONTAL EARTHQUAKE ,
WORST CASE TOWARDS
DOWNSTREAM, PW1,DUE TO
TRIANGULAR PORTION
PW2,DUE TO
RECTANGULAR PORTION
PW3,DUE TO SMALL TRIANGULAR
PORTION ON UPSTREAM
HYDRODYNAMIC FORCE , Pe
WAVE FORCE ,Pw
M+VE/MVE =
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9.4 .FOR 5/10 UPSTREAM SLOPE
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FORCE NAME MAGNITUDE (KN) LEVER ARM
(M)
MOMENT DUE TO FORCRE
AT TOE (KNM)
WEIGHT DUE TO TRIANGULAR
PORTION W1
WEIGHT DUE TO RECTANGULAR
PORTIONW2
WEIGHT OF SMALL TRIANGULAR
PORTION ON UPSTREAM W3
WEIGHT OF WATER SUPPORTED
ON DOWNSTREAM W4
WEIGHT OF WATER SUPPORTED
ON UPSTREAM(RECTANGLE) W5
WEIGHT OF WATER SUPPORTED
ON UPSTREAM(TRIANGLE) W6
UPLIFT U1
UPLIFT U2
UPLIFT U3
UPLIFT U4
WATER PRESSURE ON UPSTREAM
FACE
WATER PRESSURE ON
DOWNSTREAM FACE
EARTH QUAKE FORCE, VERTICAL
(UPWARD)
HORIZONTAL EARTHQUAKE ,
WORST CASE TOWARDS
DOWNSTREAM, PW1,DUE TO
TRIANGULAR PORTION
PW2,DUE TO
RECTANGULAR PORTION
PW3,DUE TO SMALL TRIANGULAR
PORTION ON UPSTREAM
HYDRODYNAMIC FORCE , Pe
WAVE FORCE ,Pw
M+VE/MVE =
-
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48/49
48
10.GRAPHICAL REPRESENTATIONS
-
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11.CONCLUSIONS