Comprehensive numerical analysis, design & behavior of some high concrete face rockfill dams (CFRDs) are given including recommendations for improvement their safety in seismic regions .

1. Analysis, design and behavior of concrete face rockfill dams (CFRDs)
1.1. Numerical analyses of CFRDs
CFRDs are different from rockfill dams with clay or asphalt concrete cores because: 1) concrete
face is impervious and acted upon by the hydrostatic pressure, causing high compressive stresses
on the soils in the lower part of the transition zones. Therefore, the upstream slope stability
generally is ignored not only in static and seismic analyses with full reservoir, but also deep
drawdown of reservoir that it is inadmissible. As the upper part of this slope (usually with
H/V=1.4-1.5) with the under-laying transition zone is not subjected to hydrostatic pressure it is
much more sensitive to maximum seismic acceleration in the upper dam part that the less steep
(H/V=1.6-1.7) downstream slope of rockfill with much more shear strength.
Until recently it was considered useless to perform numerical analyses of CFRDs and
promoters of these dams claimed that their design was result of only experience and empirics.
A number of incidents affected several recent high CFRDs, which has enlighted the interest of
numerical models to keep control on extrapolation towards higher dams. It has been shown that
not only stresses increase proportionally to the dam height, but even the dam stability. The valley
shape has been identified as an important factor, which induces bank-to-bank movements of
rockfill and very high compressive stresses in concrete face. Such problems are indeed quite
complex for numerical analyses, because:
• The problem is in general tridimensional (3D),
• The response of rockfill to loads requires non-linear constitutive laws with rather large
displacements, including sliding movements along the rock abutments.
• The huge contrast between the large, deformable rockfill and the slender, rigid concrete
face creates numerical problems, all the more as sliding may occur along the contact surface
between both materials.
Fig. 1.1 gives an example of model mesh for CFRD,
where rockfill and concrete face are presented with
volume finite elements. In case of rock foundation it
can be omitted from the model due to its very low
compressibility, compared to the rest of the model.
Fig. 1.1. Finite element 3-D model of CFRD: 1- Left
dam end; 2 – Crest; 3 – Right crest end; 4 – Upstream
concrete face; 5 – Rock foundation shape.
In this context, Problem 10B “Analysis of CFRD including concrete face loading and
deformation” was proposed for the 10th
bench workshop, based on information of the 145 m high
Mohale CFRD in Lesotho. Four solutions were presented, with results under the form of
displacements and stresses in the fill during construction, stresses and joint openings in the
concrete face. Stresses consistent with the damages observed in the prototype were given by 2
solutions. The main reason for these damages was identified as a high compressibility of rockfill
under high stresses, due to the breakage of rock particles.
Recently many 140-200 m high CFRDs (Mohale dam in Lesotho, Barra Grande and Campos
Novos in Brazil, etc.) have serious problems with intense cracking of concrete face and large
opening of perimeter joints that’s results in dangerous seepage and subsequent high-cost repair.
It should be emphasized that three recent incidents, including the Mohale dam, show the need to
carefully evaluate and analyze every aspect of a project when extrapolating from precedent. This
should be based on good engineering judgment and complemented with detailed analysis tools.
1.2. Behavior of concrete face of CFRDs during first impounding of the reservoir
The hydrostatic water pressure is pressing the concrete face and underlying transition zones.
Thus, the shear resistance against sliding of the concrete face on these zones is also growing with
increasing water pressure. At the same time the water pressure prevents the separation of the
concrete face from the soil of underlying transition zone. Cracking and damage of concrete face
is more likely to be expected in its upper part. At greater water depth local joint damage in the

2. concrete face due to compression and shear but also opening of vertical joints must be expected,
leading to increased leakage.
Untill recently the trend in CFRD design, based on the intuition of specialists, was to pay
great care on the placing of rockfill materials just below the concrete slabs with which these
dams are provided, and to accept much less care in the downstream area (thicker layers, lower
quality of rock, etc.). Some of these dams have shown many damages on slabs and high leakage,
due to excessive and uneven deformability of rockfill zones.
Accurate models with non-linear properties of rockfill have shown the adverse effect of
excessive compressibility of the downstream shell on the deformations imposed to the concrete
face (Anthiniac & al., 2002). The influence of excessive downstream slopes has also been put
into evidence. It is still difficult to obtain realistic rockfill properties from laboratory tests, due to
the size of finite elements and samples. Research is underway to understand the plastification
phenomenon at the scale of the block, whose objective is to provide an extrapolation law to
derive the behavior of large size rockfill from more manageable samples with only small blocks.
One of the difficulties brought by non-linear process in FE analyses is the need to check the
process convergence. Non-linear software generally use only a global convergence criterion,
based on the proportion of unbalanced energy relative to the total deformation energy. This
criterion as proved to fail in some specific cases, e.g. opening of joints in a concrete slab of a
CFRD. The reason is that even a small unbalanced local force may prevent a whole structure
from collapsing (this is the “zipper” effect). Only the engineer can detect such critical cases, and
it is therefore necessary that all software with non- linear capabilities propose means to detect
(and visualize) the amount of local unbalanced forces, at different steps of the analysis.
1.3. General seismic resistance of CFRD
The following failure modes due to seismic actions are considered for CFRDs:
(1) sliding of shallow materials along planar surfaces;
(2) wedge failure or deep-seated rotational failure (Seed et al., 1985);
(3) vulnerability of perimetric joints (Wieland, 2008) as the joint (protected with filters) is a
critical element and washing out of foundation soil is to be prevented in leakage case;
(4) cracking of concrete face due to high compressibility of the upstream transition zones. Use
in these zones well graded and compacted fine and coarse-grained soil of low compressibility
and their compaction can minimize cracking of concrete face;
5) long-term settlements of well compacted rockfill is in the range of 0.1-0.2 % of the dam
height. Strong ground shaking can produce its settlements in the range of about 0.5-1.0 m.
For assessment of the seismic performance of concrete face, the analysis of the effect of the
cross-canyon earthquake component is to be made to receive realistic values of dynamic stresses
in the concrete face and its response to these forces. The behavior of the rigid concrete face for
in-plane motions is very different from that of the rockfill in CFRD, thus the rockfill motion in
crest direction will be restrained by the concrete face. Therefore, for cross-canyon vibration, the
rigid concrete face attracts seismic forces from the dam. Hence, very high stresses may develop
in the face. Shear failure and/or spalling of concrete may occur in the highly stressed joints.
The recent case of CFRD serious damage and concrete face intense cracking was registered in
156 m high Zipingpu CFRD (China), which was designed for peak ground acceleration of 0,26g.
The dam was subjected to very strong ground shaking of Wenchuan earthquake (magnitude 8.0)
in May 12, 2008. The seismic intensity at the dam site in the range of 9-10 (Chinese seismic
scale) was beyond the value accepted in the design. During the earthquake the reservoir level
was low that was the main cause of the crest dam damage and concrete face cracking. On the
crest the recorded peak accelerations were over 2g; however, as the concrete crest behaved
differently from the dam body and since the concrete part also separated from the rockfill the
dynamic behavior of the concrete dam crest was quite different from that of the rockfill.
After the earthquake the maximum settlement at the dam crest was 735 mm and the horizontal
downstream deflection was 180 mm. The cross-canyon deformation of both abutments was 102

3. mm. Due to the reservoir low level at earthquake, it is difficult to estimate what the dam
behavior, the concrete face and waterproofing system would have been if the reservoir were full.
1.4. General recommendations for dynamic analysis of CFRDs
3D dynamic response of the system “dam-foundation-reservoir” affects the values of joint
opening of concrete face, the condition of the dam contact with abutments, behavior of control
gallery and overall picture of displacement and stress fields.
1. The boundaries of computational domain of dam foundation are appointed from the
condition of their sufficient remoteness so, that their effects on dam behavior would not be
significant. Justification the length of dam foundation in dynamic problem is complicated by the
need to eliminate the possibility of wave reflection from boundaries of computational domain.
Modern programs, such as FLAC, ADINA and Abaques allow on boundaries of the selected
computational domain to apply conditions of passing or absorption of seismic waves.
2. Degree of reliability of the results of dynamic analyses significantly depends on the
likelihood of estimated conditions on contact elements of the system. On contacts of the face
slab with transition zone should be placed one-sided links (contact works only in compression)
taking into account friction between concrete face and transition zones. FLAC, ADINA and
Abaques programs allow to realize these conditions.
3. An important issue is the choice of material models of the system “dam-foundation”.
Modern computers and software allow realizing in analyses different models of dam materials:
for concrete – elastic models, for soils – nonlinear elastic, elasto-plastic, plastic, etc. However,
there are great difficulties in selection of reliable dynamic parameters of materials of the system.
4. In dynamic (seismic) analysis the stress-strain state of the system from the static loads
(hydrostatic pressure of reservoir and dead weight of dam and face) should be considered as an
initial stress field (with zero displacements).
5. It is recommended to apply the seismic load (real and synthetic accelerograms) on the
lower boundary of the computational domain of foundation. It is permissible to apply the seismic
load directly to the bottom of the dam, if in the estimated accelerograms the dam influence on
them is already considered.
6. Modern computers and software allow taking into account in the dynamic analyses the loss
of energy due to internal friction by entering into the equations of motions the corresponding
damping coefficients.
7. With a full formulation of the problem (taking into account contact and material
nonlinearity of the system, with incorporating into computational domain the foundation) it is
required the solution by direct stepwise integration.
8. In the static analysis it is required the sizes of finite elements to be selected roughly so, that
in the zones of proposed changes of stress signs were at least five elements.
9. In the dynamic problems the sizes of elements must be no more than 1/5 of the length of
the shortest seismic wave. Researcher should choose, if program allows, a computational method
(explicit or implicit): from which the required step solution for its stability or accuracy depends
on. However, this solution step must be agreed with the step of the digitizing of accelerograms.
As a result of the studies carried out by varying design parameters of materials of the system a
researcher can get all necessary information the development to justify the dam and face slab. If
there is full information the development the dam structure is not a problem.
1.5. General design recommendations for seismic safety of high CFRDs
For the design of high CFRDs in highly seismic regions the following principal measures are
recommended, which can improve their seismic safety and behavior:
(1) downstream slope flattening in the upper part of CFRD (≈0.2H) to reduce its seismic shear
deformations;
(2) sufficient freeboard (accounting crest settlements and gravitational waves in the reservoir);
(3) wide crest (improves safety of the crest part of dam and increases resistance against
overtopping from gravitational waves);
(4) use of geogrid and other techniques to strengthen both slopes of crest part of CFRD;

4. (5) proper selection of dam materials and their zoning in dam body: well-compacted gravels
or crushed stones in the upstream transition zones and pebbles in the central dam part to decrease
their compressibility and deflection of concrete face during the reservoir impounding, solid
rockfill in the downstream slope with its maximum angles of inner friction under seismic loads;
(6) in gravel-fill CFRDs the upstream drainage zone with its horizontal part of coarse gravel
protected with filters should be provided to allow free draining of water leaking through the
cracked concrete face and further evacuating of water through gravel-fill without its piping;
(7) new effective method of decrease (up to 50-55%) of concrete face deflection by using
poor RCC zone instead of the upstream transition zone or by sluicing this zone with cement
mortar. This method was proposed in design of 275 m high Kambarata-1 CFRD in Kyrgyzstan
and 190 m high Sogamoso CFRD in Colombia;
(8) provision of bottom outlet to lower the reservoir if the concrete face or water-proofing
system is damaged;
(9) concrete face slabs with smaller width to decrease their non-uniform deformations near
steep abutments;
(10) arrangement of reinforcement of the concrete face to improve its load bearing capacity
in-plane and out-of-plane and its ductility;
(11) arrangement of proper joint system including horizontal joints and selection of the joint
width to account for the reversible nature of seismic response;
(12) water-proofing system of face slabs and plinth joint to account for static and seismic
movements of the joint.
References:
Kreuser H. (2000). “The use of risk analysis to support dam safety decision and management”, General
Report to Q.76, 20th
ICOLD Congress, Beijing, China.
Chen S.H., Wang J.S., Zhang J.L.,(1996).”Adaptive elasto-plastic FEM analysis for hydraulic
structures”. Journ. of Hydraulic Eng., 19 (2), 68-75.
Ghrib F., Leger P., Tinawi R., Lupien R. (1997). “Seismic safety evaluation of gravity dams”
Hydropower and Dams, Issue 2, pp. 126-138.
Fanelli M., Salvaneschi P. (1993). “A neural network approach to the definition of near-optimal arch
dam shape”. Dam Engineering, Vol. IV, Issue 2.
Carrere A., Colson M., Goguel B. (2002). “Modeling: a means of assisting interpretation of reading”.
Proc. 20th
ICOLD Congress (Beijing), Q.78, R.63, Vol. 3.
Anthinianc P., Carrere A., Develay D. (2002). “The contribution of numerical analysis to the design of
CFRD”, Hydropower and Dams, Vol.9, Issue 4.
2. New structures of high concrete face rockfill dams (CFRDs)
Many high (more than 100 m) CFRDs have serious problems with intense cracking of concrete
faces and large openings of perimeter joints that results in dangerous seepage and subsequent
high cost repair (A. Marulanda, 2006). The new effective method to prevent or mitigate these
problems was proposed for 275 m high Kambarata-1 CFRD in Kyrgyzstan and 190 m high
Sogamoso CFRD in Colombia, both in very seismic regions.
2.1. Kambarata-1 CFRD (design variant, H=275 m, Kyrgyzstan) on rock foundation
• This dam was designed in the USSR as a rockfill dam built by the directional blasting of rock
banks of the dam site. At present, there is an urgent need for an independent international design
expertise of the dam due to its complex environmental and technological problems that include
the unpredictable results of the great explosion of rock banks of the dam site.
• Taking into account these problems a new design variant of 275 m high CFRD was developed
with the field-proven technology of its construction.
• Since the dam height is 40 m more than height (235 m) of Shubuya CFRD in China and dam is
located in a high seismic region of 9 grade per MSK-64 scale, the special measure was proposed
to reduce the concrete face deflections (normal to face): the 3-6 m thick upstream transition
gravel zone was replaced by roller compacted lean concrete (RCC) with low compressibility.
• 2D analysis of the stress-strain state by ADINA program with the elasto-plastic Mohr-Coulomb
model of rockfill and RCC zone with different schemes of dam construction and reservoir filling

5. showed that the concrete face maximum deflection can be reduced in two times comparing with
the upstream gravel zone that greatly increased the dam safety.
• The confined dam profile and high speed of its construction will provide a great technological,
economic and environmental advantages comparing with the old design of blasted rockfill dam.
Fig. 2.1. Longitudinal section and cross-section of Kambarata-1 CFRD (H=275 m)
Fig. 2.2. Structural details of Kambarata-1 CFRD (H=275 m)

6. A. Results of 2D static stress-strain analysis of the 275 m high Kambarata-1 CFRD
with the upstream transition gravel zone 2B under concrete face
Fig. 2.3. F.E. mesh for 3 stages of construction. Fig. 2.4. F.E. mesh for 5 stages of construction.
Results of 2D static analysis for 5 stages of dam construction (Fig. 2.5-2.8) showed that vertical
compressive stresses are distributed uniformly through the dam height, reaching 6 MPa in the
dam heel. In the upstream transition gravel zone under the concrete face there is a concentration
of the compressive stresses between 0.6 and 2.6 MPa.
Fig.2.5. Horizontal displacements, m. Fig. 2.6. Vertical displacements, m.
Fig. 2.7. Horizontal stresses, Pa. Fig. 2.8. Vertical stresses, Pa.
B. Results of 2D static stress-strain analysis of the 275 m high Kambarata-1 CFRD
with the upstream supporting zone of lean RCC under concrete face
Fig.2.9. Horizontal displacements, m. Fig. 2.10. Vertical displacements, m.
Fig. 2.11. Horizontal stresses, Pa. Fig. 2.12. Vertical stresses, Pa.
Conclusions
1. For dam construction in 5 stages the concrete face maximum deflection is equal to 120 cm,
which is 20% less than the same deflection for 3 stages.
2. Reduction of face deflection with RCC supporting zone is very effective: the face maximum
deflection is only 50 cm or 2.4 times less than face deflection with the gravel transition zone.

7. 3. CFRD variant with lean RCC zone as a support for concrete face provides a great reduction
of the cost and time of dam construction compared with the rockfill blasted-type dam. Therefore,
CFRD variant is to be considered, as a principal one in the final design.
2.2. 190 m high CFRD Sogamoso (Colombia, under construction) on rock foundation
The 2D stress-strain state analysis of Sogamoso CFRD was made by ADINA program with
elasto-plastic model of dam materials with Mohr-Column criterion. The great influence of
consequence of dam construction and reservoir filling on stress-strain state of dam was received.
The new effective method of decrease (40-55%) of deflection of concrete face by inclusion of
6-3 m thick RCC supporting zone (instead of upstream transition zone of gravel, 2B) under the
concrete face was proposed for this dam.
Fig. 2.13. Cross-section of Sogamoso CFRD (190 m) with upstream RCC coffer-dam (h=36 m)
Table 1. Design parameters of Mohr-Coulomb elasto-plastic model for dam materials
Parameters Zone 3А Zone 2B
(RCC)
RCC
coffer dam
Zone 3D Zone3B Zone 3C
Deformation modulus,
MPa
50 500 500 20 40 30
Poison’s coefficient 0,3 0,2 0,2 0,33 0.32 0.33
Dry density, t/m3
2,0 2,35 2,35 1,93 2.04 1.83
Angle of internal friction φ
(grades)
42 40 40 35 44 35
Cohesion, MPa - 0,1 0,1 - - -
Fig. 2.14. Five stages of dam construction considered in static analysis of stress-strain state

8. Fig. 2.15. Finite element mesh (846 super elements) in static dam analysis of stress-strain state
Fig. 2.16. Horizontal displacements (m) in Sogamoso CFRD with RCC support zone under concrete face
Fig. 2.17. Vertical displacements (m) in Sogamoso CFRD with RCC support zone under concrete face
Conclusions
1. For 5 stages of dam construction and reservoir filling the maximum deflection of concrete face with
underlying 2B transition gravel zone (3-6 m wide) can reach 180 cm.
2. In case of replacement of the transition zone 2B by RCC 3-6 m wide supporting zone the maximum
deflection of concrete face will be only 95 cm that greatly improve the dam safety.

9. 3. Static and dynamic analyses of the heightening (from 43 to 82 m) of
concrete face gravel dam CFGD Limon (Peru)
3.1. Introduction
In June 2012 the Government of Lambayeque province (Peru) invited me as an international
consultant and member of ICOLD Committee on Dam Design to perform the expert validation
of design of the heightening of concrete face gravel dam (CFGD) Limon from 43 to 82 m. The
dam is one of the main element of project, called “Proyecto Especial Olmos–Tinajones (PEOT)”.
The hydraulic (transfer) scheme of Olmos multi-purpose project (mainly for hydropower and
irrigation purposes) includes the TransAndes water-transfer 26 km long tunnel now completed.
The 82 m high Limon CFGD is located on the right bank of the Huancabamba river in the
remote region of Andes with a very high seismicity (North-East of Peru, 980 km from Lima).
In the first PEOT project, developed by Hydroproject Institute (Moscow) in 1982, the variant
of 82 m high Limon rockfill dam with clay core was adopted as one-stage dam construction. But
later due to the political and financial problems in Peru the project implementation was delayed
for nearly 20 years and was resumed as a two-stage construction by BOT scheme, proposed by
Odebrecht construction company (Brazil). The company changed the Soviet design of one-stage
82 m high Limon traditional rockfill dam in favor of two-stage CFGD (43 and 82 m high).
3.2. Seepage analysis Limon CFGD (H=82 m) and its alluvial (40 m deep) foundation
In the figure 3.1a is presented the geometry of dam with zones of materials and its 40 m deep
alluvial strata of foundation in channel section 10-10' and their permeability coefficients. In the
figure 3.1b is presented the finite element mesh of dam and its foundation in channel section 10.
Fig. 3.1a. Zoning and permeability of soils of CFGD Limon H=82 m and its foundation in channel section
Fig. 3.1b. Finite element mesh of CFGD Limon H=82 m and (40 m deep) foundation in channel section

10. Fig. 3.2a. Equipotential lines of the total seepage heads in rock foundation below the concrete diaphragm
The results of the equipotential lines of total seepage heads in the rock foundation below the
plastic concrete diaphragm are presented in the figure 3.2a, verifying the significant reduction of
the total seepage heads by the effect of the plastic concrete diaphragm in the dam foundation.
Also, in the figure 3.2b is verified the significant reduction of the seepage pressure heads in the
rock foundation mainly due to the plastic concrete diaphragm.
Fig.3.2b. Equipotential lines of seepage pressure heads in rock foundation below the concrete diaphragm
Table 3.1 shows the unit seepage flows in the dam foundation for construction stages of H=43
m and H=82 m in sections 8-8' (in right abutment) and 10-10' (channel section) below the
concrete diaphragm, in the central dam axis and below the dam toe. The relationship of unit
seepage flows in section 8-8' shows that seepage flow in the foundation of the dam H=82 m
would be more than twice the seepage flow in the foundation of the dam H=43 m.
Table 3.1. Unit seepage flows in the dam foundation for construction stages of H=43 m and H=82 m
Dam Section
Unit seepage flows (m3
/s/m)
Below concrete
diaphragm
In axis of dam
cross-section
Below toe of
downstream slope
I Stage
H = 43 m
8 - 8' 1.373 x 10-3
1.37 x 10-3
0.744 x 10-3
10 - 10' 1.495 x 10-3
1.38 x 10-3
0.652 x 10-3
II Stage
H = 82 m
8 - 8' 2.865 x10-3
2.759 x 10-3
1.904 x 10-5
10 - 10' 3.163 x 10-3
2.791 x 10-3
0.536 x 10-3
Relation
QH82/QH43
8 - 8' 2.09 2.01 2.56
10 - 10' 2.12 2.02 0.82

11. 3.3. Seismic (dynamic) analysis of 82 m high Limon CFGD under MCE action (Amax=0.57g)
The main results of dynamic nonlinear analysis of stress-strain state of Limon CFGD (H=82 m,
variant 2 with additional downstream rockfill zone) with full reservoir under Maximum Credible
Earthquake (MCE) action of the Mar-Chile Earthquake accelerogram are given in fig. 3.3-3.15.
Another MCE of the Lima-Peru Earthquake accelerogram was considered also in the dynamic
analysis, but its action was less dangerous than that of the Mar-Chile Earthquake accelerogram.
In fig. 3.3 the accelerogram of Mar-Chile Earthquake normalized to the maximum acceleration
of Amax=0.57g is shown. The Mar-Chile Earthquake with the return period T=5000 years and
Amax=0.57g corresponds to the recommendations of ICOLD Bulletin 148 (2010) and was much
more dangerous than adopted in previous (2009) brazilian design: Amax=0.39g, T≈1000 years.
The static and dynamic analyses of stress-strain state of Limon CFGD (H=43 and 82 m) were
made by FLAC software (USA), which was estimated in the ICOLD Congress (Canada, 2003) as
one of the best software for dynamic analyses of large rockfill dams including CFRDs. The finite
element model of Limon CFGD (H=43 and 82 m) with its foundation is shown in the fig. 3.4.
Fig. 3.3. Accelerogram of Mar-Chile Fig. 3.4. The finite element model of Limon CFGD
Earthquake normalized to Amax=0.57g (H=43 and 82 m) with its foundation
Parameters of the elasto-plastic model with Mohr-Coulomb criterion for dam materials and
foundation soils in static analyses of Limon CFGD (H=43 and 82 m) are given in the table 3.2.
Table 3.2. Parameters of Mohr-Coulomb model in static analyses of Limon CFGD (H=43 and 82 m)
Numbers and names of
zones of dam materials
and foundation soils
Material
or soils
Dry density
and void ratio
Parameters of deformation Parameters of shear
strength of materials
γdr, t/m3
n E
(MPa)
Angle of
dilatancy (0
)
ν C (MPa) ψ(0
)
1-st stage dam (H=43 m)
1, 3. Foundation Alluvium 2,15 0,2 108 0 0,30 0 42
2. Diaphragm Concrete 2,25 0 320 0 0,40 0,4 30
4. Plint slab Concrete 2,5 0 20000 0 0,17 1,0 60
5. Embankment zone Gravels and
pebbles
2,2 0,15 168 0 0,30 0 46,5
6. Transition zone Gravels 2,15 0,2 150 100
0,33 0 42
7. Transition zone Sand 2,1 0,25 100 100
0,33 0 40
8. Concrete face Concrete 2,5 0 20000 0 0,17 1,0 60
2-nd stage dam (H=82 m)
9. Embankment zone Gravels 2,2 0,15 168 0 0,30 0 46,5
10. Embankment zone Gravels 2,2 0,15 168 0 0,30 0 46,5
11. Transition zone Gravels 2,15 0,2 150 100
0,33 0 42
12. Transition zone Sand 2,1 0,25 100 100
0,33 0 40
13. Concrete face Concrete 2,5 0 20000 0 0,17 1,0 60
14. Downstream zone
with 2 berms
Pebbles 2,1 0,25 150 0 0,30 0 46,5

12. Fig.3.5. Scheme of CFGD Limon (H=42 and 82 m) Fig.3.6.Scheme of CFGD Limon (H=43 and 82 m) with
(adopted variant with d-s zone 14 with 2 berms) variable shear angles of gravel and pebble zones 10-11, 15-17
Table 3.3.Values of shear angles of gravel and pebble zones 10-11, 15-17 depending on normal stresses
Normal stresses, σn , MPa 0,2 0,5 0,8 1,0 ≥1,2
Shear angles  (0
) of gravel and pebble zones 46,50
46,30
42,00
41,10
40,00
Scheme of zoning of CFGD Limon (H=82 m) with variable shear angles of gravel and pebble
zones 10-11, 15-17 (Fig.3.6) was used in the pseudo-static analyses of the downstream slope
stability under action of the acceleration in dam foundation Ahor =2/3• Amax =2/3• 0.57g=0.38g.
Fig.3.7. Distribution of seismic accelerations through Fig.3.8.Factors of seismic (Fmin=1,19>Fperm=1,06) and static
the dam height (H=82 m) using shear wedge method stability (Fmin=1,69>Fperm=1,25) of downstream slope
The distribution of seismic accelerations through the dam height was received according to
Russian seismic design norms for dams (SNiP-2003) using the shear wedge method (Figure 3.7).
Figure 3.8 shows results of static (the most dangerous circular surface 2) and seismic (the most
dangerous circular surface 1) stability of downstream slope of Limon CFGD (H=82 m) taking
into account the variable shear angles of gravel and pebble zones 10-11, 15-17. This figure show
that the minimum factor of the downstream slope stability under action of seismic loads is more
that permissible as per design norms SNiP-2003 (Fmin=1,22>Fperm=1,06) and corresponds to the
deep circular sliding surface between the dam crest and upper alluvial layers of dam foundation.
The comparison of results of the seismic stability analysis of the downstream slope of Limon
CFGD (H=82 m) with additional pebble zone 14 with two berms (fig.3.5) with results of the
same analysis of the dam but without the additional zone show that the inclusion of this zone in
the downstream slope provide a significant increase of the minimum factor of the downstream
slope stability from 1.05 up to 1.22).
Below in figures 3.9-3.12 the main results of dynamic nonlinear analysis of stress-strain state
of Limon CFGD (H==43 and H=82 m, variant with the additional downstream pebble zone) with
full reservoir under action of MCE of the Mar-Chile Earthquake accelerogram are presented.
Parameters of Mohr-Coulomb model used in the dynamic nonlinear analysis of Limon CFGD
(H=43 and 82 m) are given in table 3.4.

13. Table 3.4. Parameters of Mohr-Coulomb model in dynamic analyses of Limon CFGD (H=43 and 82 m)
Note: (σm) – medium stress (effective) in kPa
Fig. A. Curves of reduction of the shear modulus G/Gmax and
initial coefficient of damping ξ,% of soils of the dam and
its foundation
Fig. 3.9. Zones of Limon CFGD (H=43 and 82 m) with the shear and tension stress state of soils
under action of SMC of the Mar-Chile Earthquake accelerogram with Amax=0.57g
Numbers and
names of zones of
dam materials and
foundation soils
Material
or soils
Dry density
and void
ratio
Dynamic
modulus of
elasticity
Edyn
,, MPa
Shear modulus
Gmax (MPa)
Initial
coefficient of
damping ξ, %
Reduction of
parameters
Gmax and ξ
γdr,
t/m3
n
1-st stage dam (H=43 m)
1, 3. Foundation Alluvium 2,15 0,2 1300 Gmax=35(σm)0,5
5 see Fig. A
2. Diaphragm Concrete 2,25 0 1600 G= Edyn
/ [2(1+ν)] 3 --
4. Plint slab Concrete 2,5 0 20000 G= Edyn
/ [2(1+ν)] 2 --
5. Embankment
zone
Gravels and
pebbles
2,2 0,15 2000
Gmax=40(σm)0,5
5 see Fig. A
6. Transition zone Gravels 2,15 0,2 1000
Gmax=22(σm)0,5
4 see Fig. A
7. Transition zone Sand 2,15 0,2 700
Gmax=20(σm)0,5
4 see Fig. A
8. Concrete face Concrete 2, 5 0 20000
G= Edyn
/ [2(1+ν)]
5 --
2-nd stage dam (H=82 m)
9. Embankment
zone
Gravels 2,2 0,15 2000
Gmax=40(σm)0,5
5 see Fig. A
10. Embankment
zone
Gravels 2,2 0,15 2000
Gmax=40(σm)0,5
5 see Fig. A
11. Transition zone Gravels 2,15 0,2 1000 Gmax=22(σm)0,5
4 see Fig. A
12. Transition zone Sand 2,1 0,25 700
Gmax=20(σm)0,5
4 see Fig. A
13. Concrete face Concrete 2,5 0 20000 G= Edyn
/ [2(1+ν)] 5 -
14. Downstream zone
with 2 berms
Pebbles 2,15 0,2 1500 G=Edyn
/[2(1+ν)] 5 see Fig. A

14. The dam zones with the shear stress state of soils are painted in orange and zones with the
tension stress state of soils are painted in blue (Figure 3.9).
Under action of the Mar-Chile Earthquake the dam would suffer elasto-plastic deformations
with large plastic displacements in the wide zone of the downstream slope (Figure 3.10).
The large plastic (residual) deformations modified the dynamic stress-strain state of the dam
and its foundation (Figures 3.10-3.11).
The horizontal and vertical displacement in the dam after the Mar-Chile Earthquake in the
upper part of the downstream slope are, respectively, 2.0 and 1.0 m; in the upper berm - 2.2 and
1.1 m; in the lower berm - 2.5 and 1.3 m and at the toe of the slope - 6.0 m and zero (Fig. 3.10).
The intensity of shear deformations (Figure 3.11) is concentrated in the narrow zone in the
lower part of the downstream slope of the dam.
Fig. 3.10. Horizontal (a) and vertical (b) displacements in Limon dam (82m) after Mar-Chile Earthquake
Fig. 3.11. Intensity of the shear deformations in Limon dam (82m) after the Mar-Chile Earthquake
Fig. 3.12. The time history of the residual horizontal (a) and vertical (b) displacements of the crest of
Limon dam (82 m) during the Mar-Chile Earthquake

15. The time history of the residual horizontal (a) and vertical (b) displacements of the dam crest
during the Mar-Chile Earthquake is shown in Figure 3.12. The maximum horizontal and vertical
displacements of the dam crest during the Mar-Chile Earthquake are, respectively, 1.5 and 1.1 m
Conclusions
1. Horizontal and vertical displacements after the Mar-Chile Earthquake of the downstream slope
(between the dam crest and lower berm) are, respectively, 2.0-2.5 and 1.0-1.3 m. The maximum
horizontal and vertical displacements of the dam crest during the Mar-Chile Earthquake are,
respectively, 1.5 and 1.1 m and after the Earthquake - 0.4 and 0.3 m. These displacements about
two times lower than those in the previous variant 1 of the dam with the downstream slope of
(V/H=1/1.7) and the under-laying rockfill without berms.
2. In comparison with the previous variant 1 of Limon dam (H=82 m) with the downstream slope
of (V/H=1/1.7) and the under-laying rockfill without berms this variant 2 of Limon dam (H=82
m) with additional gravel zone with two berms on downstream slope is much more stable and
safe under action of very strong MCE of the Mar-Chile Earthquake. Therefore, this variant 2 of
Limon dam can be adopted in the following detailed final design of 82 m high CFRD Limon.
4. Example of dynamic analysis of 150 m high CFRD
As an example the dynamic analysis of 150 m high CFRD with upstream and downstream
slopes 1.5H/1V is considered.
Fig. 4.1 shows 3D model of the system dam-foundation and its discretization by finite elements.
Totally about 150 thousand finite elements, mainly 3D elements with 8-nodes and partially 3D
elements with 6-nodes in dam contact with abutments. Concrete face is simulated by 3D shell
elements. On face-dam contacts, in the deformation joints of face, on face-abutments contacts
one-sided links (contact works only in compression) are organized, taking into account the
friction on the contact surfaces. Some researches were previously specified on 2D models.
Fig. 4.1. 3D model of dam for analysis of 3D
stress-strain state:
1 - concrete face; 2 - rockfill; 3 - loose layer;
4 – foundation massif
Special combination of loads is considered:
hydro-static pressure of reservoir, dead weight of the dam (the initial stress state) and seismic
load in the form of three-component accelerograms applied to the lower surface of foundation
massif. Rockfill and transition zone materials are considered as a linear-elastic, nonlinear elastic
and elastic-plastic medium.
Fig. 4.3 shows the development of detachment (separationt) of the dam with face from both
abutment slopes. The upper figure shows the detachment of the dam and face from the left
abutment slope after 8 seconds of the earthquake. As can be seen from the lower figure, after
11.4 seconds of the earthquake detachment is observed only on the right abutment slope in the
central section of the dam (approximately under its crest).

16. Fig. 4.3. Deformations of the dam during seismic load
a - upstream view, t=8 sec; b - deformations of the central longitudinal section of the dam,
t=11.4 sec.
Fig. 4.4 shows the openings of face joints under static loads and after 8 sec. and 8.6 sec. of
earthquake.
Fig. 4.4. Openings of joints of concrete face:
a - under static load; b - under earthquake action in zone A of face after t=8 sec;
b - under earthquake action in zone A of face after t=8 sec.
It should be noted that implementation of full computational studies required to obtain enough
reliable dam response, required high qualification of researchers and appropriate computational
and technical support.
5. Prospects of construction of high CFRDs in Russia
Analysis of intensive construction of high CFRDs in China, Brazil, Colombia and some other
countries and experience of their operation have shown that under certain natural conditions
(favorable topographic and geotechnical conditions, availability of the necessary constructional
materials, etc.) the choice of this type of dam compared with the other type (rockfill dams with
clay or asphaltic concrete cores, RCC or concrete dams) can be the most efficient and
economical solution. This is due to the much smaller volume of rockfill materials, hydraulic

17. safety of CFRD with high piping resistance, static and seismic stability and effective compaction
of its rockfill and transition zones, concrete plinth and faces, retaining wall on dam crest.
According to long-term plan of the development of hydropower industry in Russia up to 2020
the main regions for construction of new hydropower plants are the North Caucasus, Altai,
Siberia and the Far East. Natural conditions for the construction of CFRs in the North Caucasus
are close enough to those conditions in which a large number of foreign CFRDs were
constructed. Therefore, CFRDs dams may be atractive especially in the Northern Caucasus and
some CIS countries (Tajikistan, Kirgizstan, Uzbekistan and Kazakhstan).
As for the construction of CFRDs in Siberia and the Far East some additional problems may
arise with regard to the concrete face behavior in its upper part under action of extreme low
temperatures. However, the experience of construction of 200 m high CFRD in Iceland shows
the ability to solve these problems.
On other side, the experience of construction of rockfill dams with asphaltic concrete cores in
Siberia, Norway and Canada shows that these dams are safer than CFRD in severe climate of
these countries.