Cfrd World No.1-2013

Feb. 2013,VOLUME 6

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CONTENTS

(No.1 Feb. 2013)

ANFISbased Multistaged Decision Algorithm for Seismic Safety Control of ConcreteFaced Rockfill Dams EHSAN NOROOZINEJAD FARSANGI. (Iran) AZLAN ADNAN Malaysia

MELDI SUHATRIL Malaysia ROZAINA ISMAIL Malaysia 1

La Yesca Hydroelectric Project Treatment of an Unstable Zone at the Left Bank GABRIEL FRANCISCO RAMÍREZ ORDAZ, ANASTACIO PÉREZ RIVERA (Mexico) 14

Design of Gongboxia Concrete Face Rockfill Dam Xiong Wen (China) 22

Publication of young and middleaged CFRD experts having made great contribution to the world CFRD construction Editorial Board 28

Technical study tours provided by ICFRD 30

ICFRD No. 1, Feb 2013

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*Corresponding Author: Ehsan Noroozinejad Farsangi

ANFISbased Multistaged Decision Algorithm

for Seismic Safety Control of ConcreteFaced Rockfill Dams

EHSAN NOROOZINEJAD FARSANGI *

Structural Earthquake Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran

AZLAN ADNAN Engineering Seismology and Earthquake Engineering Research Group, Faculty of Civil Engineering,

University of Technology Malaysia (UTM), Johor Bahru, Malaysia

MELDI SUHATRIL Department of Civil Engineering, Faculty of Engineering, University of Malaya (UM), Kuala Lumpur,

Malaysia

ROZAINA ISMAIL Faculty of Civil Engineering, University of Technology Mara (UiTM), Selangor, Malaysia

Abstract

In this study, we used hybrid intelligent system called NeuroFuzzy to predict the seismic response of Bakun dam

which is the second tallest ConcreteFaced Rockfill Dam (CFRD) in the world. At the first stage Bakun dam has

been numerically analyzed for its nonlinear behaviour under earthquake excitation to generate numerical data to

be used in the training of the NeuroFuzzy system by means of NLFEM. To this end the dam has been subjected

to a Local synthetic excitation so that the generated data could be rich enough for the training of a general Neuro

Fuzzymodeller of the dam response. ANFIS gives us the combination of computation and learning capabilities of

ANN and the human knowledge representation of FL, While ANN are lowlevel computational structures that

perform well dealing with raw data, FL deals with reasoning on a higher level, using linguistic information acquired

from domain experts. The results obtained in this study prove that the method has been successful regarding the

generalization capabilities of the trained NeuroFuzzymodeller where other earthquakes than those used in its

training have been used in its testing and verification. Once the NeuroFuzzymodeller is trained, it can predict the

response of the dam to any earthquake without the need to be updated.

Keywords: CFRD, ANN, FIS, NLFEA, NeuroFuzzymodeller

1. Introduction An earthquake is produced by the sudden rupture or slip of a geological fault. Faults occur at the intersection of

two segments of the earth’s crust. Peninsula Malaysia lies in the Eurasian Plate and also within the Indian

Australian Plate. Geologically, small faults also exist in East Malaysia. Records have shown that we do

sometimes experiences some offset tremors originating from the Indonesian zone. Thus there is a need for some

seismic checking to be incorporated in the design process so that the structures would be resistant to earthquake.

These days, the seismic verification of structures has dramatically evolved. Malaysia is surrounded by countries

such as Indonesia and Philippine that has experienced many great earthquakes; hence it would be unwise to

totally ignore the effects of earthquakes on structures in Malaysia [Noroozinejad E. and Adnan. A., 2011; Adnan

A. , 2010; Adnan. A. et al., 2005; Adnan. A. et al., 2002].


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The behaviour of CFRDs subject to earthquakes is complicated because dams might experience cracking at

places where the induced tensile stresses are higher than the tensile strength of concrete. Cracking and also

material nonlinearity results in nonlinear behaviour which is hysteretic too. The nonlinear hysteretic response of

CFRDs can be modelled using any of the commercially available finite element analysis softwares or especial

computer programs which have been developed for the modeling of this type of dams. Nonlinear analysis by

conventional methods is time consuming though very helpful. Also when it is desired to provide a precise

numerical model for the nonlinear behaviour of a dam, it is necessary to identify the parameters of the material.

To this end, it is required to collect data on the real response of the dam and then try to determine the parameters

of the material to be used in the computer programs, so that the simulated response to be as close to the

observed response as possible. The material model obtained from the identification is often approximate and

hence the analysis based on the model will not be precise either [Noroozinejad E. and Adnan. A., 2011; Adnan A.,

2010].

Deterministic and statistical methods have been used to develop models to predict the nonlinear structural

behaviour of the dams [ICOLD., 2003]. The hybrid method, which is a combination of the two fundamental

methods, has also been applied to forecast behaviour [Perner F and Obernhuber P., 2010]. The deterministic

modelling requires solving differential equations for which closed form solutions may be difficult or impossible to

obtain [SzostakChrzanowski A. et al., 2005]. Therefore, numerical methods, such as the finite element method,

are used. The advantages of statistical methods, such as multiple linear regressions (MLR), are simplicity of

formulation and speed of execution. In the MLR model, it is possible to identify the contribution of each loading

action to the structural response [Mata J., 2011]. In order to correlate the dam behaviour with the intrinsic

parameters of the dam, such as structure size, boundary conditions and elastic properties, structural identification

techniques are applied to analyse the collected measures, [De Sortis A. and Paoliani P., 2007; Fedele R. et al.,

2005; Ardito R. et al., 2004].

The dam deformation under the seismic excitations is a typical example of nonlinear behaviour [Cao M. et al.,

2009, Bayrak T., 2007]. System identification of concrete and concretefaced Rockfill dams can be categorised as

one of the most significant aspects of dam engineering, [Karimi I. et al., 2010]. Identification and prediction of the

dam deformation are complex tasks for which nonparametric models are often used. [Gülal E. et al., 2010] used

linear ARX (autoregressive with exogenous inputs) model calculated from a 3D finite element model to assess the

impact of horizontal displacements in the dam. The displacement of one or several points of the dam is a

nonlinear function of hydrostatic pressure, temperature and other unexpected unknown causes. In the last decade,

soft computing techniques have been extensively applied for complex time series prediction. Neural network

modelling and identification are effective tools for approximation of uncertain nonlinear dynamic systems. Feed

forward and recurrent neural networks have been widely studied in nonlinear systems identification [Chen CH.,

2005; Gupta P and Sinha NK., 1999; Yazdizadeh A. and Khorasani K., 2002; Yu W. and Li X., 2001; Gao Y. and

Er MJ. NARMAX, 2005; Yu W., 2004].

In recent years, Takagi–Sugeno fuzzy systems, as a class of fuzzy models, have been applied as nonlinear

system identifiers [Abdelazim T. and Malik OP., 2005; Banakar A. and Fazle Azeem M., 2011]. The Takagi–

Sugeno fuzzy model provides satisfactory results in describing behaviour of complex and uncertain systems.

[Babuška R. and Verbruggen H., 2003] showed an overview of neurofuzzy modelling methods for nonlinear

system identification.

ANFIS (Adoptive Neuro Fuzzy Interface System) is based on fuzzy inference system which also has been

successfully applied to solve many problems. The ANFIS, first introduced by [Jang JSR., 1993], as a universal

approximator and as such is capable of approximating any real continuous function on a compact set to any

degree of accuracy [Jang JSR., 1997]. In hydrology field, [Nayak P.C. et al., 2004] presents the application of


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ANFIS to hydrologic time series modeling, and is illustrated by an application to model the river flow of Baitarani

River in Orissa state, India. ANFIS was used to construct a River flow forecasting system in [Firat M. and Güngör

M., 2007], and the River Great Menderes of Turkey was chosen as a case study in that paper. [Mousavi S.J. et al.,

2007] applied ANFIS and fuzzy regression method to infer operating rules for reservoir operations. [Abolpour B. et

al., 2007] presents ANFIS method to simulate optimizing allocation of scarce water resources in Iran. [Chang L.C.

and Chang F.J., 2002] presented a new approach to improve realtime reservoir operation. The approach

combines two major procedures: the genetic algorithm (GA) and ANFIS. In 2006, Chang also dealt with predicting

water level problem in reservoir, only to select different input variables and no tide considering [Chang F.J. and

Chang Y.T., 2006]. It demonstrates that the ANFIS can be applied successfully and provide high accuracy and

reliability for infrastructure’s response forecasting. But as can be seen from the previous researches, there has

been no study on the application of ANFIS on the seismic response behaviour of infrastructures especially dams,

to this end the authors decided to implement this techniques for the seismic safety control of CFRD’s.

In the present work, the ANFIS is used for structural identification of the Bakun dam which is the second tallest

ConcreteFaced Rockfill Dam (CFRD) in the world and located in east Malaysia. The objective of this study is to

develop a Neurofuzzy identification model for the dam crest and midheight displacements prediction and to

demonstrate its application to identifying complex nonlinear relationships between the input and output variables.

The proposed approach based on the ANFIS identification can be a very helpful tool for modelling of timevarying

behaviour of engineering structures.

1.1. Importance of the study

There are many reasons for Malaysia to worry about earthquake. New revelations indicate Malaysia is moving

closer towards the rumble zone. Malaysia is inching closer to rumble zones and will not be immune to earthquake

forever. Year after year, neighboring tectonic plates inch towards from all directions and on mounting because the

Australian, Eurasian and Philippine plates around Malaysia are moving. Recent research indicated that

Peninsular Malaysia does lie on faults but have been known to be nonactive faults. Malaysia is located in low

seismic activity area but the active earthquake fault line through the centre of Sumatera just lies 350 km from

peninsular [Adnan A. , 2010; Adnan. A. et al., 2005].

Sabah, which experienced the highest earthquake magnitude recoded with 4.8 Richter in the last century

occurred about 90 KM from Miri, Sarawak have cause several building crack. The plates are moving closer

toward and shift a few centimeters was recorded after the incidents have been reported [Ismail R. et al., 2011;

Adnan. A. et al., 2002].

Fig. 1.


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2. Case Study

In this study, the nonlinear response of the Bakun dam under a local earthquake excitation has been

modeled numerically. Malaysia undertakes to construct one of the largest CRFD dams in the world; the Bakun

dam (see Fig. 2 for the geographical location). The dam, which is the largest in Southeast Asia, is 207m high and

crest length of 750m with an installed capacity of 2400 Mega Watt (MW), and a lifespan of 500 years. The

minimum and maximum operating levels are 195 and 228m above sea level (asl).The impoundment of the dam

will inundate 69,640 ha of forest ecosystem, an area larger than the size of Singapore. The project is estimated to

cost RM6 billion ($1US=RM3.1, RM=Ringgit Malaysia).

Fig. 2. The geographical location & Upstr eamDownstr eam view of Bakun Dam

3. NonLinear Finite Element analysis of Bakun dam

The mathematical model of the dam in point is based on a 3D finite element (FE) discretization (Figure 3),

consisting of 1367 brick elements (each one with 20 nodes and quadratic interpolations) and 48 wedge elements

(with 15 nodes and quadratic interpolations).The dam was subjected to different ground excitations which

included a local synthetic, Kobe and El Centro earthquakes. Response of the dam crest and midheight consisting

of the time history of its acceleration, velocity and displacement was recorded throughout the time.

Fig. 3. Finite Element model of Bakun dam

Figure 4 shows the time history and Fourier Amplitude Spectra of the local synthetic earthquake used in the

training of Neurofuzzy modeller.

Dominant Frequency: 17.81 Hz


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Fig. 4. The shake wave of the Local synthetic ear thquake and its dominant frequency

3.1. Constitutive models 3.1.1. Clough–Duncan model

The Clough–Duncan model [Clough GW. et al., 1997] is often

used for the soil–structure interface. This model only

describes the tangential stress–displacement relationship as follows:

= (3.1)

kst, is described using the following equation:

= . . 1.

.(3.2)

Where k0, n, Rf

3.1.2. Modified ideal model

The modified ideal Elastoplasticity model has a different formulation on the tangential stiffness, as shown in

the following equation, with considering the effect of normal stress:

= . , <

= 0, = (3.3)

in the finite element modeling procedure, Clough

Duncan model is implemented.

4. Fuzzy Inference System

Ebrahim Mamdani of London University [Mamdani E.H., 1974] followed Lotfi Zadeh’s fuzzy theory and applied it

to control steam engine and boiler combination in 1975. He used a set of fuzzy rules supplied by experienced

human operators.

Some called this a Mamdani method or Mamdanistyle fuzzy inference. It usually consists of four steps:

Step1: Fuzzification

First of all, transform the crisp inputs into fuzzy sets, and determine the degree to which these inputs belong to

each of the appropriate fuzzy sets. The membership function is the way that we determine how fuzzy they are.

Step2: Fuzzy rule base


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Fuzzy rule base is where the system stores all information and knowledge involving with the proposed problem. A

typical rule of Sugeno’s model might be written as:

If x is A 1 and y is B 1 Then z = f (x, y) (4.1)

Where x and y are inputs and z is a crisp function in the consequent.

Step 3: Fuzzy Inference Engine

The fuzzy inference engine is the brainlike module of the whole system. According to the fuzzy rule base in

step2, it can simulate human’s inference, thinking, and decisionmaking abilities to solve problems.

Step 4: Defuzzification

The last step of fuzzy inference system is defuzzification, which consists in transforming the fuzzy outcome into a

nonfuzzy output.

Fig. 5. Fuzzy Inter face System

4.1. ANFIS

Eq. (4.2) is a typical Sugeno fuzzy rule, and z can be either a constant or a linear function of the input variables.

When z is a constant, a zeroorder Sugenofuzzy model is obtained. When z is a firstorder polynomial, that is:

z = f (x, y) = px+qy+r (4.2)

If there are two input variables, the rules will be:

If x is A1 and y is B1 Then f1= p1x+q1y+r1 (4.3)

If x is A2 and y is B2 Then f2= p2x+q2y+r2 (4.4)

Generally, the ANFIS model is a neural network with five layers. Fig. 6 displays the ANFIS architecture (b)

and the inferring process (a).

Fuzzification Inference Engine

Defuzzification

Fuzzy rule base

x 1 x2 y

(a)

(b)


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Fig. 6. ANFIS architecture for twoinput Sugeno fuzzy model with four rules

The following description details calculating procedure of ANFIS layer by layer: Layer 1:

Layer 1 is input and fuzzification layer as step 1 in last section.

Layer 2:

Layer 2 is the rule layer. A rule neuron receives inputs from the respective fuzzification neurons and

calculates the firing strength of the rule it represents. The symbol is the operator product, and the output of

neuron i in Layer 2 is obtained as:

O2, (4.5)

Layer 3:

Layer 3 is the normalization layer. The capital letter N on the neuron denotes normalization. Each neuron in

this layer calculates the normalized firing strength of a given rule. Thus, the output of neuron i in Layer 3 is

determined as:

O3,i=w = , i = 1,2 (4.6)

Layer 4:

This layer is the defuzzification layer. A defuzzification neuron calculates the weighted consequent value of

a given rule as:

O4,i= = ( + + ), = 1,2 (4.7)

Layer 5:

This layer is designed to calculate the summation of outputs of all defuzzification neurons in former layer.

O5,i= = , = 1,2 (4.8)

5. Simulation Results and Discussion

The major objective of the study presented in this paper is to construct ANFIS models to predict the crest and

midheight displacements of a CFRD. The selection of an appropriate set of input variables during the ANFIS

development is important for modeling. In the previous researches [Rankovic´ V. et al., 2012], the hydrostatic

pressure and the thermal load have been the main components to be taken into account when modeling the dam

displacement, but in this study as the deformations caused by earthquakes are our main concern, the seismic

record and the dam’s seismic responses are entered in our simulation as well. The hydrostatic load can be

accurately modelled on the basis of the reservoir water level. Description of the thermal load requires a detailed

knowledge of the temperature values at several points of the structure [De Sortis A. and Paoliani P., 2007]. This

level of knowledge is usually not available. Then, the thermal load can be represented by the parameter d. While

suggesting the model for the horizontal displacements of an arch dam, [Demirkaya S., 2010] chose the following

input variables: the water level of the reservoir, the values of the thermometer embedded in the upstream and

downstream face and in the middle of the dam and the air temperature.

The dam displacement is a typical example of timevarying behaviour. In this study, two ANFIS models with

feedback loops have been developed for computing the crest and midheight displacements. The inputs of the

model are u1=

January 1st, u2=h where h is the water level, and the history of response and excitation which are Yi

=displacement, Y’i= velocity and X”i= earth acceleration at current time steps, X”i1 and X”i+1 for the previous


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and next time steps. The range of the input variable h is between 198 and 218 m. The MATLAB Fuzzy Toolbox is

used for the implementation of the fuzzy model.

The number of the ANFIS inputs is determined by the input and output lags, nu1 , nu2 , nYi , nY’i , nX”i1 , nX”i ,

nX”i+1 and nYi+1 , nY’i+1, respectively. Prior knowledge, insight in the process behaviour and the purpose of

modeling are sources of information for the choice of the possible number of lags [Babuška R. and Verbruggen H.,

2003]. In this study, the satisfactory accuracy is obtained for all input lags=1 and nYi+1=2 and nYi+1 =3 for both

models. The input vector to the Takagi–Sugeno fuzzy systems is:

( + 1) = [ ( ), ( ), ( ), ( ), "( 1), X" ( ), "( + 1)] (5.1)

The predicted value of the crest and midheight displacements at time step k depends on the measured values of

the displacement at time steps k1, k2 and k3 [y(k 1) , y(k 2), y( k 3)] , the water level value, value of the

parameter d and the history of response and excitation at time steps (i1) , (i) and (i+1). The effects of the

hydrostatic pressure and thermal load on the dam displacements are taken into account in two ways: explicitly

through the parameters d and h as inputs and implicitly through the measured values of the displacement as

inputs into the model. Therefore, the impact of each variable on the model output cannot be considered

separately.

Fig. 7 Architecture of the proposed NeuroFuzzy modeller with its feedback loops

The time effect is incorporated into the model by including the measured values of the displacement at previous

time steps as inputs into the model. These measured values depend not only on variations of the hydrostatic

pressure and temperature, but also on other causes including degradation of material properties during the

previous and current earthquake events.

Selection of parameters for the training process and their impact on the ANFIS have been addressed in the

literature [Rankovic´ V. et al., 2012; Jang JSR., 1993]. The initial step size is defined to 0.01. The step size

decrease rate is 0.95 and the step size increase rate is 1.05. Fuzzy partitioning of the input variables of the ANFIS

is realized by selection of the two primary fuzzy sets.

The prediction performances of the soft computing models were evaluated using the correlation coefficient (r), the

mean absolute error (MAE) and the mean square error (MSE):

=( ( ) )( ( ) )

( ( ) ) ( ( ) )

(5.2)

MAE= |y (k) y(k)| (5.3)

"

"

"

1

2

NeuroFuzzy Modeller


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MSE= (y (k ) y(k)) (5.4)

Where ym and y denote the model output and the measured value, respectively; y and y denote their

average values, respectively, and N represents the number of observations.Smaller MAE and MSE values ensure

better performance. The NARX model [Sjöberg J. et al., 1995] assumes that the observations are sampled with

the same frequency. In our simulation, the training data set was complete. Many techniques for the estimation of

missing data can be applied even if the training data set is not complete [Nelwamondo FV., 2009]. In the case

when the model is used and there is no measured displacement value y(ki), the estimated value ym(k i) can be

used.

The three most common use membership functions are triangular, trapezoid and bellshaped. It could not to be

found out which membership function is the most appropriate for this model until they are tried [Wang A.P. et al.

2008]. The performance criteria of different membership functions (see MF Type in Table 1) were compared to

each other. From Table 1, it is showed that all of the models with different MFs simulated similarly in training sets,

especially in MSE (only an interval of 0.008 between maximum and minimum). That means that these ANFIS

models simulated well. It is apparent that the errors are higher in validation sets, and performs diversely in various

MFs. The triangular MF displays the best results with a higher r and a lower MAE and MSE. Regardless of a little

bit higher MAE and MSE in training sets, the trapezoid MF also has excellent results in validation sets. Broadly,

we can say that these ANFIS models predict crest and midheight displacements in terms of earthquake loadings

very well.

Table 1. Per formance parameter s of the ANFIS models for differ ent member ship functions (Local EQ) Model Member ship

Function Training Validation

r MAE MSE r MAE MSE ANFIS model

(Crest) Triangular 0.969 0.731 0.241 0.897 0.682 0.761

Bell 0.956 0.743 0.236 0.881 0.692 0.783 Trapezoid 0.967 0.762 0.244 0.888 0.701 0.778

ANFIS model (midheight)

Triangular 0.971 0.723 0.239 0.901 0.623 0.693 Bell 0.954 0.745 0.237 0.882 0.672 0.696

Trapezoid 0.966 0.761 0.241 0.891 0.693 0.688

In our study, the proposed Neurofuzzy identification model shows efficiency in forecasting the crest and mid

height displacements, and it is in accordance with results of other authors. The prediction performances of the

ANFIS identification models trained and tested with 338 data samples which were obtained by 3D NLFEA. In the

training process, the ANFIS 236 samples were used. For the first ANFIS model, the coefficient of correlation

values for the best training and test sets were 0.969 and 0.897, respectively. The best correlation coefficient of

0.971 for the training and 0.901 for the test set were obtained for the second ANFIS model. The decrease in the

measurement frequency yields models with a slightly higher coefficient of correlation values for the training set,

but a slightly lower coefficient of correlation values for the validation set.


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Fig. 8. ANFIS Forecasting (Best MF) vs. NonLinear FEA results for Crest Disp. (Local synthetic excitation)

Fig. 9. ANFIS Forecasting (Best MF) vs. NonLinear FEA results for MidHeight Disp. (Local synthetic excitation)

Fig. 10. ANFIS Forecasting (Best MF) vs. NonLinear FEA results for Crest Disp. (Kobe)

Fig. 11. ANFIS Forecasting (Best MF) vs. NonLinear FEA results for Crest Disp. (ElCentro)


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When the ANFIS model is compared with the FEM model as in Figs. 811 it is seen that the ANFIS model is as

good as the FEM model. The physicsbased model of FEM represents our best understanding of the physical

process. In this model, the relations among the input and output variables are welldefined. Therefore it has

universal applicability. Using this model, it is possible to obtain spatial and temporal variations of the state

variables over the domain of interest under different values of the model parameters. Such information might be

essential, especially for investigating any undesired cases that might happen and be detrimental to dam safety.

On the other hand, the FEM model can be more effective when extensive data in the domain of interest is

available.

However, in practical situations satisfying all the data needs of a comprehensive FEM is seldom available due to

time and budgetary constraints. For example, in this case study, no data was available on the spatial distribution

of hydraulic parameters of the geological formation and the drainage outflow. Furthermore, there is always a

problem of convergence and instability in the numerical solution of the highly nonlinear differential equations of

the physicsbased model.

The ANFIS is a much simpler model, which has an ability to recognize the pattern between input and output

variables when provided with sufficient measured field data. It should be, however, noted that ANFIS is a data

driven black box model which does not reveal any explicit relation between input and output variables, thus it

does not provide much insight into understanding the physical problem. Furthermore, although ANFIS has very

successful interpolation capability, it lacks the extrapolation ability for the cases for which it is not trained.

6. Conclusions

The prediction of the future dam displacements is a challenging problem in dam engineering. The behaviour of a

dam is a nonlinear function of earthquake loadings, hydrostatic pressure, temperature and other unexpected

unknown causes such as the result of time effects. This paper studies identification of nonlinear structural

behaviour using the ANFIS. Comparison between the modelled displacement values obtained by the ANFIS and

the NLFEA shows that Neurofuzzy identification can be an effective tool for the approximation of uncertain

nonlinear structural behaviour of the CFRDs. The performances of the soft computing models were tested using

correlation coefficients, the mean absolute error and the mean square error.

One of the benefits of this approach is that once the Neurofuzzy modeller is trained, it can be used in the

analysis directly to replace the integration methods and thus can significantly reduce the time required for analysis.

However the method requires a considerable time for the training of the Neurofuzzy modeller. It is expected that

the method can be extended for application to the dynamic analysis of stress and strain inside the dams too.

The main limitation of this approach lies in the fact that it does not directly consider mechanical properties and

possible damage. Additional analysis in the form of nondestructive tests (statical and dynamical), computational

mechanical modeling and inverse analysis are also required.

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14

LA YESCA HYDROELECTRIC PROJECT

TREATMENT OF AN UNSTABLE ZONE AT THE LEFT BANK

GABRIEL FRANCISCO RAMÍREZ ORDAZ

ANASTACIO PÉREZ RIVERA

ICA Construcción Pesada

Mexico

During excavation of the diversion tunnels at La Yesca hydroelectric project geologic conditions were exposed

that posed a risk in its continuity and feasibility therefore demanding an important instrumentation campaign to

identify the mechanism of the geologic fault known as Colapso that allowed the implementation of immediate

solutions for its stabilization during the construction stage and the arrival at acceptable safety factors for the

operation of the project.

1. INTRODUCTION

La Yesca hydroelectric project constitutes part of the Santiago River Hydrologic System; it is located along the

namesake river at a distance of 105 km to the NW of the town of Hostotipaquillo, State of Jalisco, between the

operating hydroelectric power stations of Santa Rosa and El Cajón, and its purpose is to exploit the water course

for power generation through two generating units with individual capacity of 375 MW.

The main structures are found distributed in both river banks; the left bank contains the diversion works and the

spillway whereas the generation works are found at the right bank and in between the embankment dam is

located with a height of 208.50 m, ranking it as the second highest dam in the world of its type.

Its construction was carried out between years 2007 and 2012 with an intensive work schedule that allowed

diversion of the river in the month of March, during the dry season of 2009, enabling the initiation of other

important stages such as the impoundment works.

The site is constituted by volcanic rocks from the Cenozoic that include andesites and diabasic dykes and it is

partially covered by tuffs, brecciatype rhyolite ignimbrites, alluvial terraces, lacustrine and pumice deposits, talus

deposits and alluvium (fig. 1).


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Fig. 1 Geologic profi le of the left bank

The structural geology considers a characteristic faulting in blocks and it is the result of one or several stages of

distension tectonics, with positioning of intrusive bodies, where lateral shifting movements also occur

2. DETECTION, STUDY AND INSTRUMENTATION OF THE LEFT BANK

At the slopes of the entrance portal of the diversion tunnels, fourbar extensometers were installed to be able to

register since March 2008 atypical displacements that accentuated in the course of the excavation works and

even more with the beginning of the rainy season of that same year.

The problem worsened when important cracks developed in the shotcrete at the various berms and after

identifying a failure surface at the excavation for road 6MI that evidenced signs of displacement and it was

therefore necessary to install a large amount of instruments (inclinometers, joint gages, piezometers and

topographic references) for the purpose of delimiting the moving mass and the depth of the failure zone so as to

be able to calculate the volume of the unstable material to implement geotechnical solutions.

In addition, automated equipment (GPSbased monitoring system, fig. 2) was installed to allow identification in

real time of important displacements but keeping safety conditions for the personnel working inside the diversion

tunnels.

Fig. 2 Instrumentation installed (manual and automated)

Manual measuring instruments and precision topographic surveys were actually very valuable to retrieve

information while borings were drilled to an average depth of 100 m for the purpose of installing inclinometers and

piezometers (fig. 3).


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Fig. 3 General view of the left bank

Inclinometer

Bartype extensometer

Threedimensional joint gages

Superficial references

Casagrandetype piezometer

To be able to install inclinometers in a timely manner, T4 equipment for water well drilling was used, achieving a

progress rate of 80 m a day for 25cm diameter borings.

3. ENGINEERING, PLANNING AND EXECUTION OF WORKS

Important effects were identified on the structures located at the left bank that resulted in major changes in the

design of the plinth, the embankment, the waterproofing barrier and the spillway works.

Based on the study and dimensioning of the geologic phenomenon of the Colapso Fault, and taking into account

the identification and determination of the magnitude of the displacements induced by the unstable block with

volume of 2.5 million cubic meters (fig. 4), that compelled the temporary suspension of the works for the

excavation of the diversion tunnels, a remediation plan was devised to start preparing the engineering of the

works that was validated by the technical staff constituted by domestic and international consultants, each of the

works and structures to be built representing a major challenge the need to arrest progress of the displacements

through an intensive work schedule supported by a great capacity of response of the human assets of the project.


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Fig. 4 View from upstream of the entrance portal to the diversion tunnels

4. Stabilization works during the construction stage

4.1 Removal and excavation of material

One of the first actions implemented was the reduction of the weight of the upper part of the unstable block

through the excavation and removal of a volume of 770,000 m3 equivalent to 1,540,000 t, therefore reducing

approximately 30% of the total weight of the unstable block being this activity carried out in three stages during

the stabilization period (fig. 5). The first stage was executed from the second half of June to the end of July 2008,

the next stage between the third week of November 2008 and the third week of January 2009, and the last stage

covered from the second week of February to the third week of May 2009. This action proved its efficiency by

registering an important decrease in the magnitude and speed of the displacements since its implementation.

Furthermore, since rock excavations were involved, blasting activities were performed controlling the load factors

and monitoring the particle velocity therefore preventing with this excessive vibrations to occur that could affect

the displacements of the unstable block.

Fig. 5 General view – Material removal and concrete dead block

4.2 Removal of material. Top part of the Concrete block

4.2.1 Concrete block at the entrance portals of the diversion tunnels


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Another important decision and action taken involved the construction of a concrete block at the lower part of the

hillside at the entrance to the diversion tunnels that, because of its location, acted as a buttress to balance the

failure mechanism of the Colapso Fault, containing a volume of 110,000 m3 equivalent to a weight of 242,000 t

that represent 5% of the weight of the unstable mass; it was built between the second half of July and the first

week of December 2008 by implementing strong logistics to respond the urgent need to arrest the displacements

and deformations of the unstable block, mobilizing additional equipment for processing the aggregates for

concrete with strength f’c = 200 kg/cm2, additional concrete mixing plants so as not to compromise the

construction schedule of the other structures of the project, and concrete hauling and pumping equipment with

which a production rate of 2000 m3 per day was reached.

4.2.2 False tunnels, rock fi ll and concrete sleeves

Complementary works were required that implied construction of 80m long false tunnels (fig. 6) based on steel

frames and hydraulic concrete, starting at the concrete monolith, upon which a fill of 250,000 m3 was placed

using rockfill material that because of their location contributed with a weight of 500,000 t to the stabilization of the

Colapso Fault mechanism.

Fig. 6 False tunnels

In addition, to strengthen the diversion tunnels at their intersection with the fault, 1m thick concrete sleeves were

built incorporating shear elements as reinforcement therefore reducing the section of the tunnels from 14 m to 12

m (fig. 7)


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Fig. 7 Stabil ization works

5. Impacts on other structures

The magnitude of the unstable rock mass also affected the structures for the gates of provisional closing and that

for the final closing required for river handling, as well as the retaining and spillway works, and readjustments

were made to the original concept for river control during the final closure of the diversion tunnels to start filling of

the reservoir; as a result, the provisional closing plugs were relocated from their original position to the front of the

110,000m3 concrete block so as to move away these elements from the unstable mass.

In the case of the final closure shaft, its execution was cancelled therefore modifying the river control procedure.

Another structure that suffered important changes in its original engineering was the embankment that rested very

close to the boundary of the unstable mass and it was decided to make a turn of 14 degrees in its axis,

maintaining fixed the abutment of the right bank and rotating the axis toward downstream therefore preventing the

embankment foundation and the plinth to be supported by the unstable block. The spillway works was the other

major structure that sustained important adjustments in its original design that referred principally to shifting the

control structure toward downstream in order to achieve an alignment of the gate zone with the new dam axis as

well as rotation of its axis by 30 degrees. The embankment rotation also affected the waterproofing plane and it

became necessary to readjust importantly the alignment of each of the galleries of this bank as well as the deep

cutoff and drainage wall.

Fig. 8 Graphic variation of displacements (no se menciona en el texto)


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6. Stabilization works for the operational stage

Since the first analyses of the Colapso Fault system, for purposes of stabilization of the unstable mass

consideration was given to the conditions likely to exist during the operation of the hydroelectric power plant,

because the stability conditions of the block are expected to vary during first filling of the reservoir, mainly due to

wetting of the failure surface and to the reduction of the contribution made by the counterweight applied (monolith

and cofferdam) when becoming submerged, including the revision of the most critical and unfavorable conditions

in the case of occurrence of a rapid drawdown of the reservoir whatever the reason, making it even possible for

the displacements of the unstable block to be reactivated; new engineering studies were made to define, for a

stage subsequent to construction, the measures and actions required during the operation.

6.1 Shearresisting shafts

An unprecedented solution in the construction of dams in Mexico was devised, consisting in the construction of

six secant shearresisting shafts (7, 8, 910, 11, 12) with variable diameters and a height of 90 m, excavated from

elevation 480.00 msnm (meters above mean sea level) and until reaching elevation 390.00 msnm (fig. 9), with a

high degree of difficulty because these shafts run through the unstable zone, cross the Colapso Fault and

become embedded into the block that evidenced no movements.

Fig. 9 Shearresisting shafts

To improve the stability conditions inside the unstable mass, consolidation treatments were made prior to the

excavation of the raises and banking of each shaft. The procedure consisted in excavating an auxiliary tunnel at

the lower part of the hillside that reaches the lowest elevation of each shaft through which the excavation works

for the raises were made and it was used to remove the muck from excavations and banking. Upon completion of

the excavation of each shaft according to the sequence established, they were filled with fluid concrete with

strength f’c=200 kg/cm2 reinforced with steel mesh at a rate of 40 kg/m3; in this concrete, classified as mass

concrete, ice was added to reach a temperature of 20°C during its placement.

6.2 Concrete sleeves and anchor plug

As part of the reinforcement of the diversion tunnels, 1m thick linings were built along both diversion tunnels,

between stations Km 0 + 055.00 and 0 + 119.00 (64 linear meters) of tunnel 1 and from Km 0 + 054.95 to 0 +

104.00 (49.05 linear meters) of tunnel 2, benefitting from the dry season of river control during which only one

tunnel remained operating to handle the flow rate, initially through tunnel 1 after lowering the gate of tunnel 2 to

allow construction of the sleeve inside the latter, and the other way around for placement of the lining at tunnel 1

diverting the river through tunnel 2.


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In addition, to increase safety along the diversion tunnels when subjected to an eventual displacement that could

happen during operation of the power station, it has been contemplated to build anchor plugs with hydraulic

concrete of f’c=250 kg/cm2 and high strength reinforcing steel with fy=8450 kg/cm2 as well as to fill the tunnels

between stations Km 0 + 020.00 and 0 + 170.00 (190 linear meters) of tunnel 1 and from Km 0 + 075.00 to 0 +

219.50 (144.50 linear meters) of tunnel 2, leaving a section of the gallery from which the works of contact injection,

consolidation and drainage cutoff wall are carried out.

On the other hand, an extensive monitoring system has been implemented for the operating stage by installing at

the various structures submersible sensors to measure displacements, the pore pressure at the fault and the

stresses inside the concrete of the shearresisting shafts. This system is basically constituted by five

inclinometers placed in situ, 10 assemblies of vibratingstring piezometers, four bartype vibratingstring

extensometers, 12 rosettes of strain gages, 10 pressure cells, three vibratingstring joint gages and five

thermocouples, as well as by the installation at the diversion tunnels of 64 platetype vibratingstring

extensometers and eight electric piezometers. These sensors will be incorporated into the Automated data

Acquisition System using close to 80,500 m of signal cable for the purpose of collecting information in real time

related to the behavior of the unstable zone even below the reservoir level.

In projects where largevolume excavations are made in the open or in underground works, it becomes important

to establish as part of the integral planning and during the construction processes considerations and facilities to

install, measure and protect the instrumentation with constant adjustments to the geological conditions of each

site and incorporating as part of the work cycles to be executed the installation of the instruments, therefore being

possible to learn through the registries of the measurements atypical situations of displacements, porewater

pressures and stresses so as to be able, in the case of them being associated to geologic faults, to develop

preventive actions that guarantee safety conditions to the personnel to pursue the works, applying geotechnical

treatments the provide the stability and achieving the expected safety factors suitable to the service expected

from each of the structures.


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Design of Gongboxia Concrete Face Rockfill Dam

Xiong Wen

(HydrOu China) 1. General

Gongboxia hydropower station is located on the mainstream of the Yellow River, on the border between Xunhua

Sala Autonomous County and Hualong Hui Autonomous County in Qinghai province, 25km away from Xunhua

county and 153km to Xining city.

It is a large scale Class I (1) project, mainly for power generation, as well as irrigation and water supply purposes.

The catchment area above dam site is 143619km2, mean annual runoff of 226×108 m3, reservoir normal storage

level at EL.2005.00m, and dead water level at EL.2002.00m, design and check flood level at EL.2005.00m and

EL.2008.28m respectively. The reservoir is a daily regulation reservoir, with a total storage capacity of 6.3×108

m3 and a regulating storage of 7.5×107 m3. The installed capacity is 1500MW, firm output of 492MW, and mean

annual generation capacity of 5.14TW∙h.

The project is composed of dam, headrace system and discharge structure. Based on topographic and geological

conditions, and for convienent construction and operation, the project is arranged as: riverbed CFRD, headrace

system on the right bank (including approach channel, concrete dam type power intake, open penstock, surface

powerhouse and 330kV switchyard), floodrelief tunnels on both banks, and left spillway, face slab seepage

control system on right bank and irrigation intakes on left and right banks after several alternatives were

compared.

The project commenced on August 8, 2001. The diversion tunnel works started on 1 July, 2000, and the river bed

was closed on 18 March, 2002. The first unit was commissioned on September 20, 2004, and the project was

completed by the end of 2006.

The dam foundation started excavation on August 15, 2001, and dam placement started on August 1, 2002. The

dam was placed up to EL.2005.50m (bottom of surge wall) on October 22, 2003. Placement of concrete face slab

started on 15 March, 2004 and completed on 3 June, 2004. The reservoir impounding started on 8 August, 2004.

2. CFRD dam

2.1 Topographic and geologic conditions The Yellow River at dam site flows toward NE30°~50°, with a flat stream channel. When the river leve at

EL.1900m in mean water period, the water surface 40~60m wide and 12~13m deep. The overburden in the river

bed is 5~13m thick. The valley is asymmetric. Rocky slope is below EL.1980.0m on the right bank, and above

EL.1980.0m is sandy loam and gravel layer of Class III terrace. The slope gradient is 40°~50°above El.1940m,

while below the slope is very steep. Except Class II terrace covered by drift bed rocks at EL.1930.0m and

EL.1950.0m on the left bank, the others are rocky slope, with an average gradient of 30° or so, and about 10m

high slope along the river is fairly steep. Main rock characters at dam site are PreSinian System gneiss, quartz

micaschist and quartzite; Caledonian period granite; Cretaceous system purple red sandstone; Teritary system

red gravel sandstone, Quaternary system

Sandy loam and sandy gravel. Basic earthquake intensity is 7 degree at dam site, and dam is designed as per the

seismic intensity of 8 degree.

2.2 Dam layout

EL. 2010.00m, with a maximum height of 132.20m, a crest length of 429.0m and width of 10.0m. The dam has a


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upstream slope of 1:1.4, and 1:1.5~1:1.3 for downstream slope, protected by dry laid stone masonry, and

provision of a 10m wide “Z” access road to the dam crest, with a composite dam slope of 1:1.79. The dam crest

has a 5.8m high “L” wall connected with face slabs and the wall bottom is at EL.2005.5m. Due to narrow valley,

the power intake is near to right abutment and the spillway is near to left abutment, therefore, 50m and 38m high

cutoff wall was provided at the connection between right abutment & station intake and the connection between

left abutment & spillway approach channel respectively to link up dam face slab (see Fig. 1).

Fig. 1 Layout of Dam

3. Design of CFRD

It describes new technology for design of dam zoning, face slab and plinth slab in combination with the

characteristics of Gongboxia CFRD.

3.1 Dam zoning

3.1.1` Principle of dam material zoning

To meet the requirement of hydraulic transition between dam materials, cushion materal (2A) is semipervious

and main rockfill (3B1) is pervious, in order to ensure fluent drainage of dam and the adjacent downstream

material against reverse filtration protection for the upstream zone, and prevent internal piping and erosion.

The upstream zone material of dam axis shall have a greater deformation modulus, which decreases from

upstream to downstream so as to ensure the coordination and continuity of deformation between dam zonings

after impoundment and minimize the influence of dam deformation on face slab to decrease the possibility of face

slab and waterstop system damage.

To make full use of excavated material from structures, for economic purpose .

3.1.2 Zoning of dam materials


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Fig. 2 Typical section of dam

According to the above zoning principles, from upstream to downstream the dam is zoned as incline loam blanket

below upstream face slab (1A) and its weighted zone (1B), concrete face slab and cushion zone (2A), cushion

subzone, transition zone (3A), main rockfill zone (3B 1, 3B 2, 3B ) and downstream subrockfill zone

(3C), as detailed in the typical section of dam (Fig. 2).

Main rockfill zone was primarily designed as 2 zonings, i.e 3B I (rockfill zone) and 3B (sandy gravel zone).

During construction, it was found by insitu trial embankment that less than 5mm grain content in excavated

material as 3B I zone filling is greater than the design requirement of below 8%, mostly 20%, reaching 26% at

maximum. Meanwhile, the field test indicated that permeability coefficient K is 103 in most cases, less than

design value (The design requires that main rockfill zone shall discharge seepage fluently, i.e., free drainage, and

K value shall be controlled in the range of 101~102.), and equal to or less than the permeability coefficient of

cushion material (2A), or transition material (3A), which differs from the concept of increasing CFRD permeability

coefficient from cushion material (2A), transition material (3A) to main rockfill zone by grade, not meet the

requirement of dam drainage. In view of the above conditions, to make full use of the excavated material, one

highly pervious zone is added [to separate 3B I zone into 2 zones of 3B I1 (strong pervious zone, 5mm grain

content is less than 8%, and permeability coefficient K is larger than 101cm/s) and 3B I2]. Hence, the main

rockfill zone includes 3 zones of 3B 1, 3B 2 and 3B .

Dam placement volume is 4.39M m3 in total. Rock excavation of the project structures is 6.067M m3, in which

highlyweathered rock is 3.782M m3 and weaklyweathered rock is 3.085M m3. By test, caculation and analysis,

most of rocks excavated from structures can be used for dam filling. Therefore, in dam zoning design, prior

consideration was given to utilize the excavated material to a maximum, and finally the excavated material used

for dam filling accounts for 2/3 total placement volume.

3.1.3 Design of concrete slab and plinth

Face slab

The thickness of face slab is determined as t = 0.3 + 0.003H, being 0.3m for the thickness of top, and 0.7 for the

thickness of bottom after calculation. Singlelayer twoway reinforcement is applied and the reinforcement rate in

either way is 0.3% 0.4%. According to the result of 3D stress and strain calculation for the embankment, the

scope of compressive joint in the valley is less and the scope of tension joint on the two banks is larger, so the

space between vertical joints is 12.0m.


25

Plinth

Plinth walls are provided at the left and right abutments of Gongboxia dam besides conventional plinths in other

locations. Considering different acting heads and foundation lithology, the plinths are designed to be 5.0m, 6.0m,

7.5m and 9.0m in width, and 0.5m, 0.6m and 0.7m in thickness. The singleway or doubleway reinforcement is

applied and the reinforcement rate in every way is 0.3%. Grouted (high strength mortar) dowels are installed in

the foundation, 3.8m into bedrocks.

Plinth walls

Considering the topographical and geological condition and composition of main structures, plinth walls are

applied at both left and right banks, which is one salient feature of this project. The application of plinth walls

makes the layout more reasonable and compact. The plinth wall is an important part of plinth, and the maximum

heights of the concrete plinth walls at left and right banks are 38m and 50m respectively.

The plinth wall at left bank is located at right side of spillway (used as right guide wall of spillway), being a

concrete gravity retaining wall and its crest elevation at 2010.0m. In the meantime, it serves as part of access

road from crest to the intake tower of left bank flood release tunnel whose total length is 50.0m. The top of wall is

8.0m wide according to the requirement of transportation (including the width of cantilever bracket support, 1.5m).

The two sides of wall are torsion faces, the left side of wall is gradually changed from a vertical to an incline of

1:0.5 and the right side is gradually changed from an incline of 1:0.5 to a vertical. The right bank plinth wall is

located at the left side of the power intake, being a concrete gravity retaining wall, its crest elevation at

2010.00m 1952.417m, and whose total length is 84.99m. According to the requirement of structure, the wall top

is 4.013.21m in width, and is an inclined slope of 1:1.5 along with the length direction. The height of wall is

gradually reduced. The right side is vertical surface, and the left side is an incline of 1:0.6. The foundation

elevation is at 1960.0m 1950.0m. One grouting and drainage gallery is provided within the wall, and the

foundation is treated by consolidation grouting and curtain grouting.

The plinth wall will bear lateral pressure of embankment rockfill during construction and the pressure of reservoir

water. Additionally, larger deformation is not allowed to be caused so as to avoid destroying the waterstops for

perimetric joints between face slab and plinth wall or tear the grouting curtain under plinth wall to split, which will

influence the normal operation of face slab. Since plinth walls hare under complicated stresses, the outline

structures should be considered as integral after the calculation, analysis and comparison of various schemes.

The calculation result shows that the left and right walls both have less tensile stress zone (with the maximum

value of 0.1MPa), the compressive stress in wall is also less, and the sliding stability of the walls has higher safety

margin.

4. Application of new technology 4.1 Slope strengthening technology by curb wall

Curb wall is a new technology for slope strengthening for CFRD. The curb wall can be constructed at the same

time of filling cushion materials, and the construction procedures such as chamfering dam face, compacting on

inclined slope and slope protection can be omitted. Therefore, the overfilling of cushion materials can be avoided

and the filling speed can be expedited, and the compactness of cushion materials on slope surface can be raised.

The erosion of cushion materials during construction can be alleviated and benefit the slope protection and

temporary water retaining and flood release.

By collecting data and analysis, site test and verification, the structure of curb wall and its control standard are as

follows:

The upstream slope of curb wall has a slope gradient of 1:1.4, the same as that of the upstream slope of

embankment. The width of top is taken as 10cm, the height of wall is the same as the thickness of laying

materials and the inner slope of concrete curb wall is 8:1.


26

The compressive strength at 28th day should not be over 5MPa, and the 24 hour compressive strength index

should be determined in principle of side wall would not collapse when cushion materials are vibrated and

compacted.

The elastic modulus should be controlled within 5000 7000MPa, and it is better to be lower than 5000MPa.

The density index should be controlled within 2.0 2.25t/m3, being close to the compact density as much as

possible.

The permeability coefficient should be controlled below 103cm/s, that is to say, consistent with the permeability

coefficient of cushion layer that is semipervious.

The surface of curb wall is sprayed with one thin layer of emulsion asphalt in order to reduce the restraint to

concrete face slab and good for cracking control.

The calculation and analysis show that, in the operation period, the compressive stress of curb wall along the

slope direction is 20MPa36MPa, the axial compressive stress is 22MPa~36 MPa, which are all higher than the

compressive strength of wall. So, the curb wall in operation time has been crushed, and its properties almost are

the same as those of cushion materials. The flexibility of face slab is 27.3cm in case of being with curb wall and

28.1cm in case of being without curb wall respectively. The tensile stress along the slope direction is 3.46MPa

and 3.52MPa respectively, and compressive stress is 6.8MPa and 7.1MPa respectively. The calculated value with

curb wall is less than that without curb wall, so it is thought that curb wall has no adverse effect on the stress and

strain of face slab. The curb wall with reasonable design of outline will not influence the safe operation of slab.

4.2 Onestage construction of face slab

The original design was that face slabs would be constructed in two stages. The firststage concrete slabs would

be constructed when embankment is filled up to 1956.0m a.s.l.and the secondstage slabs would be constructed

when embankment is filled up to 2005.5m a.s.l., as this construction could enable the embankment to retain water

during flood reason and also is prevailing in the world. But due to the particular flood release condition of

Gongboxia in construction term(the flood in construction term can be regulated by Longyangxia project upstream),

so the inflow in flood season would be smaller and could be retained by the cofferdam, besides the full section

filling simultaneously also facilitate the onestage face slab construction. Additionally, considering there occurred

some problems in staged construction for other projects at home and abroad, (for example, the settlement of

embankment may cause the emptiness at the top of firststage face slabs, and the upper embankment filling

would impact the firststages face slabs), and construction term for dam is very tight because the river closure

time was postponed for 4 months, so onestage construction of face slab can mitigate the influence of

initial(including construction term) settlement of embankment on face slabs, simplify construction procedure and

expedite the process. The calculation and analysis demonstrate that the stress and flexibility of face slabs

concreted in one stage would be lower than those of face slabs concreted in two stages (the flexibility is reduced

from 23.3cm to 20.5cm, and the stress along the slope direction is reduced from 10.04MPa to 6.32MPa), and the

stress and strain conditions are fundamentally same, and the displacement of perimetric joint slightly decreases.

These demonstrate that onestage cast of face slabs is favorable for the dam safety. All parties’ efforts have

made it, the face slabs were concreted in one stage, and the length reaches 218m that is the longest recorded in

the world.

4.3 Construction method of embankment

The Gongboxia CFRD is originally designed to retain water in flood season, and the embankment cannot be

constructed in fullsection but filled in stages. During construction, according to forecast flood and regulation of

upstream large reservoir, the inflow flood is reduced, and the aim of retaining water all over year by cofferdam is

viable. The method of fullsection filling and evenly rising is adopted betimes so as to minimize the uneven

settlement and adverse influence on face slabs. After calculation, the settlement of embankment by fullsection


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filling is reduced from 137.3 cm ~140.9 cm to 99.69 cm ~103.6 cm compared with the temporary section of

embankment filling.

4.4 Aseismic design

The analysis result of static and dynamic stress and deformation shows that the amplified times of earthquake

reaction acceleration on the dam crest would reach 3.7, which means the dynamic reaction is larger and the

upper part of downstream dam slope might collapse. Therefore, the following measures are adopted in the design

of embankment.

Change the distribution of downstream dam slope gradient, make it appear as: three grades, the upper is gentle

and the lower is steep, the gradient for most top is 1:1.5, for the middle part, 1:1.4 and for the lower part, 1:1.3, so

as to mitigate the damage of earthquake to dam crest.

The downstream slope above EL. 1980.00m is protected by stone masonry.

The transitional materials 3A are used to raise the structural strength of dam crest above EL.1995m. Tiebars

are preembedded within embankment above 1980.00m and connected with stone masonry slope protection so

as to strengthen the integrity of dam crest and increase the aseismic ability of dam crest. The preembedded tie

5. Conclusions The monitoring data in dam construction term shows that the uneven settlement of embankment is smaller, and

the total settlement to the time of impoundment does not reach the 1% of dam height. The observation data after

impoundment shows that the settlement and deformation of embankment are slow and even. The regular pattern

is normal, and the settlement deformation is only 47.80m. It is demonstrated that the design is reasonable, safe

and successful.

In the design process, comprehensive considerations are given to the topographical and geological conditions,

absorbing advanced dam design technology and experience at home and abroad, such as providing one highly

pervious zone, reasonable aseismic measures, concrete extruded curb, plinth walls at right and left sides, full dam

section placing, continuous construction of concrete face slab in one round, which sped up construction progress,

assured construction quality and reduced project investment. In a word, application of these advanced technology

and engineering measures made great success in Gongboxia project and the benefits are noticeable.

The monitoring data after impoundment shows that the dam seepage flow is only 68L/s. It demonstrates that the

design for slab, plinth, left and right plinth walls and waterstop system is safe and reasonable.

References J. L. Justo, et al, The Upstream Facing of Martin Gonzalo Rockfill Dam, Transactions of 16th Congress on Large

Dams, Vol. 2, Q.61, R.47, 1988.

J.G.P. Barnes. Programming in Ada. Addison–Wesley, Wokingham, England, third edition, 1989.

Bofang Zhu, Priciples and Application of Finite Element Method, Beijing, Water Conservancy and Hydroelectric

Press, 1979 (in Chinese).


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Publication of young and middleaged CFRD experts

having made great contribution to the world CFRD construction

CFRD WORLD, (ISSN 19979185) http://www.icfrd.org/index.php/cfrdworld is a Journal

of International CFRD Society (ICFRD) http://www.icfrd.org/index.php/abouticfrd, sponsored by ICFRD and

HydrOu China http://hydrou.icfrd.org/index.php?option=com_content&view=article&id=3&Itemid=271, the

only one international magazine for the world CFRD construction. It mainly carries the technical documents and

papers, and articles of CFRD construction, and the articles from water power, environmental

protection, flood control and international tourism sections as well.

CFRD WORLD will publish the good achievements of young and middleaged CFRD experts who have made

great contribution to the world CFRD construction on a selective basis.

A. Requirements

1. The applicants must have more than 10 years’ working experience in the CFRD field such as in design,

construction, research , operation management or construction management or supervision,or consultation on

CFRDs or materials or instrumentations for CFRDs or any other fields involved in CFRDs;

2. The applicants must take part personally in 2 100m CFRDs or more in design, construction, operation

management or construction management or supervision, or consultation, etc incase with less than 5 years’

experinces;

3. Present the convincing proofs to the CFRD WORLD Editorial Board http://www.icfrd.org/index.php/editorial

board at [email protected] ;

4. Send 1 or 2 papers on CFRDs written by the applicant him/herself;

5. A Recommendation Letter should be sent to the Editorial Board at [email protected] singed

with Recommendations by ICFRD Deputy Secretary General http://www.icfrd.org/index.php/secretariat or

Chairman of ICFRD http://www.icfrd.org/index.php/professionalcommission in the applicant’s country. (The

applicant should inform the Editorial Board in advance if no ICFRD Deputy Secretary General exists in his/her

country or region ).

Two or more members of ICRRD or the CFRD WORLD Editorial Board can sign

the Recommendations jointly instead in no ICFRD Deputy Secretary General country.

B. Application


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1. Applicants shall send the CFRD Expert Applications with the achivements gained by him/her in the world

CFRD construction to the Editorial Board.

2. Invite two or more referrers to write their Recommendations jontly on the Recommendation Letter .

C. Approval

1. The application will be approved by the ICFRD Expert Committee http://www.icfrd.org/index.php/expert

committee within 15 days after receiving an application.

2. The applicant will receive an Acceptance or Nonacceptance as a Young and Middleaged CFRD Expert

within 20 days after he/she sends out his/her application to the Editorial Board.

3. Publish the achievements and resume of the Young and Middleaged CFRD Expert with 2 or more pages of

publication free of charge for 3 issues of CFRD WORLD.


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Technical Study Tours provided by ICFRD

1. Three Gorges study tour , 3 days

D1 Visit Three Gorges Project (TGP) site, the biggest hydropower project in the world.

D2 The Chinese dam experts who took part in the construction of the TGP present their experiences based on the visitors' requirements.

D3 The Chinese dam experts who took part in the construction of the TGP make some technical consultation on the technical problems put forward by the visitors

Three Gorges Project

The Three Gorges Project is the biggest water conservancy project ever built in the world. The dam

site is situated at Sandouping ,Yichang City, China about 38 km upstream from Gezhouba Project.

The project is composed of a dam, two power stations and navigation facilities. The spillway section is

placed in the center, while the powerhouses are arranged on its both sides. The permanent navigation

structures are located on the left bank side The dam is of a concrete gravity type. The total length of

the dam axis is about 2,309 meters with the crest elevation at 185m There are 14 generating sets of

hydro turbine generator units installed in the left powerhouse while 12 generating sets in the right.

Thus, there are 26 sets of turbine generator units in total 700MW for each totaling 18,200MW in

installed capacity that will produce 84.7TWh of electricity output annually The first stage

construction lasts 5 years from 1993 to 1997. The second stage construction lasts 6 years from 1998 to

2003.The third stage construction lasts 6 years from 2003 to 2009. After the project completed the

total storage capacity of the reservoir is 39.3 billion m³ with the normal pool level at 175m. The total

length of the dam axis is 2309.37 meters. The spillway section, which is located in the middle of the

river course, is 483 meters long in total. It is the most important project functioning as a backbone in

flood control system to protect the areas in the middle and lower reaches of Yangtze River. With a

22.15 billion m³ of flood control storage capacity of the reservoir, the Jingjiang River Section is able

to raise its flood control capability from the present 10year frequency to the 100year. And the 660km

long waterway from Yichang to Chongqing is obviously improved, making it possible for 10,000 tons

of barge fleet to sail upstream directly to Chongqing now.

The Three Gorge Dams is the largest dam in the world, as wide as the Golden Gate Bridge and twice

as tall, capable of generating 18 gigawatts of hydroelectric power.


31

2. Shuibuya CFRD study tour , 3 days

D1 Visit the Shuibuya CFRD site, the highest built in the world.

D2 The Chinese CRRD experts who took part in the construction of the dam present their experiences according to the visitors' requirements.

D3 The Chinese CRRD experts who took part in the construction of the dam make some technical consultation on the technical problems put forward by the visitors.

The Shuibuya CFRD

233m high Shuibuya CFRD, 46m higher than Aguamilpa Dam in Mexico, is the highest CRFD in the world by now. Successful completion of Shuibuya CFRD not only broke the theoretical constraint on CFRD over 200m as accepted by international dam engineers but also made technical breakthrough on the construction of highest CFRD in karst region.

3. J iangpinghe CFRD study tour , 3 days

D1 D2 Visit the Jiangpinghe CFRD site

D3 The Chinese CRRD experts who are taking part in the construction of the Jiangpinghe CFRD make some technical consultation on the technical problems put forward by the visitors.

The Jiangpinghe CFRD

The Jiangpinghe Hydropower Station in China closed successfully on 20, Dec. 2008. The Station has a

CFRD height of 219m, which is the 2nd highest of the same type in the world.

The station is located in Hefeng County, Ehshi Prefecture, Hubei Province, in China which is about

380 km away from the Shuibuya CFRD site. The dynamic total investment is 35 hundred million or

more. The main purpose of the project is power generation and accompanies with miscellaneous

functions such as flood control, tourism, navigation, and aquiculture. The total power of the station is

450,000kw with 2 vertical shaft mixed flow turbine-generator sets of 225,000 each, long term

average annual energy of 963800000 kWh. The first generating unit will predict to be put into

operation in the end of 2013 and completed in Dec. 2014. The normal reservoir level is 470m and the

total reservoir capacity is 13.66 hundred million m 3 .


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4. Gezhouba dam study tour , 2 days

D1 Visit the Gezhouba dam site

D2 The Chinese dam experts who took part in the construction of

the Gezhouba project and the Three Gorges project make

some technical consultation on the technical

problems put forward by the visitors.

Gezhouba Hydropower Station

The station is built at the entrance to the Xiling Gorge, and near the Three Gorges Hydropower Plant in the downtown of Yichnag City, the first hydropower station in the trunk of the Yangtze River, with an installed capacity of 2.73 million kw. The Gezhouba dam is a conveyance system for “ the Three Gorges Project”. The Project includes the barrage, the power plant, the shiplock, the flood discharge gates and the fishway, etc. It is also one of the largest hydropower station built in China. The embankment is 2,561 m long and 70m high which controls a drainage area of 1,000,000 km². With 21 generating units the hydropower station generates 13.8 billion KWH a year.

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