**3. Application area**

#### **3.1. Safety of dams**

82 Multivariate Analysis in Management, Engineering and the Sciences

detecting the main instruments.

**2. Problem statement** 

The aim of this paper is to identify the tools that are the most significant for the analysis of a dam behavior, which maximizes the effectiveness and efficiency of the analysis of the readings. It shows a methodology based on the field of Multivariate Analysis, applied to the Hierarchical Cluster Analysis in order to identify the groups of instruments similar to Ward's linkage method. The factor analysis of the strain gauge of each instrument group was also applied, performing the hierarchical cluster of monitoring instruments in dams,

This chapter is organized as follows: Section 2 features the problem statement which addresses the importance of the safety on dams and the risks faced when dam rupture accident occurs. Section 3 describes the application area focusing on the safety of dams, on the conditions of load and on the conditions of the monitoring instrument. Section 4 approaches a "research course". Section 5 describes the used data and the Multivariate Statistical Analysis techniques. Section 6 shows the status. Section 7 shows the results.

Once the potential risks and losses as a result of rupture accidents on a dam can reach large scales a safe project and adequate construction as well as a correct operation on dams are concerns of Brazilian and worldwide engineers. Additionally, an effectively done monitoring on large dams is essential for the safety of its structure. By aiming the safety of the dams, International Guidelines and many helpful discussions about this subject have

In Brazil, guidelines that aim the safety of the dams were published by the *Comitê Brasileiro de Grandes Barragens* (Brazilian Committee on Large Dams), see [2]. The *Comissão de Constituição e Justiça e Cidadania do Congresso Nacional)* (The Constitutional, Justice and Citizenship Committee of the National Congress) approved, on 06/23/2009, the proposal that requires the Executive Power to establish a National Policy on Dams Safety. Its aim was to endow the Public Power with a permanent instrument for the inspection of over 300 thousand dams in the country. The text that has been questioned is the surrogate for the Law Project 1181/03 [3]. The original proposal, the Law Project 1181/03, (*Projeto de Lei – PL 1181/03)*, written by Leonardo Monteiro, defines safety guidelines for the construction of

The concerns about the Brazilian Constitutional Public Powers is due to the recent rupture of the Dam of Câmara, (in the State of Pará - PA), in 2004; the rupture of the diversion structure of the Dam of Campos Novos, (in the State of Santa Catarina - SC), in 2006; the rupture of the Dam of Algodões I, (in the State of Piauí - PI), in 2009; and other accidents of

According to [4], the catastrophes have been opportune signs for the examination of the criteria of the existing projects and for the selection of more efficient methods and

Section 8 approaches the future researches. Section 9 shows the results.

been proposed and conducted, such as the one from the [1].

dams and landfills of industrial liquid wastes.

smaller magnitude.

monitoring safety of dams.

The principles established on NBR 8681 – *Ações e Segurança das Estruturas* (Actions and safety of structures) [7] conceptualizes the safety of the concrete constructions of a dam. For concrete gravity-dam projects, some verification corresponding to the stability analysis are necessary in order to evaluate the safety of the movements of: sliding, overturning, floating, tension at base and on structure, deformations, consolidation and vibrations.

The stability of dams must be primary analyzed during the phase of the project. The geometry of the structures and the property of the materials involved must be well considered, as well as the load condition. Some of the basic load conditions are shown on Figure 1.

**Figure 1.** Illustration of the basic conditions of load and lack of stability of gravity concrete dams.

Through Physics, it is possible to explain that the difference of the water level (downstreamupstream) generates a hydraulic gradient between the dam downstream and upstream

making the water of the reservoir to try passing through upstream in order to archive a hydraulic equilibrium. To do so, the water percolates through the foundation mass of the dam. During this process, the infiltrated water generates vertical forces acting upward over the dam, these forces are called uplift pressure in dam. The resultant of these forces is represented by Fuplift. Furthermore, the water from the reservoir generates horizontal forces that act downstream-upstream over the dam. These forces are called hydrostatic pressures against the dam wall. The resultants of these forces are represented by Freservoir. These two resultant forces are called destabilizing forces. As for the force P (dam weight) it is a stabilizing structure force. The combination of Fuplift and Freservoir can cause the overturning and the slipping of the dam, not just because of the efforts and moment when it is directly applied, but also for the relief of the weight of the structure itself (in case of uplift pressure).

Itaipu Hydroelectric Power Plant Structural Geotechnical Instrumentation

Temporal Data Under the Application of Multivariate Analysis – Grouping and Ranking Techniques 85

In [10] shows correlations between the types of instruments that are usually used for the auscultation on concrete dams, and the primary types of deterioration of concrete dams. According to the author, the multiple extensometer for example, is related to the monitoring of deteriorations caused by sliding, different declinations, land subsidence of the upstream

The measurement of the declinations is one of the most important observations for monitoring a dam behavior during the period of construction, of dams filling and operation. The measurement of the declination can be performed through a multiple point rod extensometer installed on boreholes [10]. Figure 3 shows the multiple point rod extensometer

**Figure 3.** Multiple point rod extensometer and a example of a typical profile of a multiple point rod

The measurements of displacements and deformation can be performed in several parts of the foundation with the usage of various rods. Among these displacement and deformations are

and an example of a typical profile of a multiple point rod extensometer at *Itaipu*.

base, and the Alkali-Aggregate Reactivity.

extensometer at *Itaipu* (Adapted from [11]).

The above described effects of loads on dams can be observed on figure 1, where the slipping (a) and the overturning (b) are emphasized.

The loading conditions and the properties of materials can change over the lifecycle of a dam, and instrumentation can identify some of these changes.

Figure 2 shows the differences in the behavior of the dam in relation to summer and winter climate conditions, as well as its consequences. In summer, an expansion of the concrete occurs, and that causes the block to tumble downstream. This overturning causes the block to compress the foundation. In winter, the concrete is compressed causing the block to tumble upstream, returning to initial position. As a consequence the pressure that occurs in summer over the foundation to be relieved. In this way, it is possible to identify a cyclical behavior of the structure, intrinsically conditioned by the environmental conditions which involve the construction.

**Figure 2.** Behavior of the dam in relation to summer and winter climate conditions (Adapted from [8]).

According to [9], the instrumentation must be used as supplement to visual inspection when executing the evaluation of the performance and safety of dams. The careful inspection of the instrumentation data can reveal a critical condition.

In [10] shows correlations between the types of instruments that are usually used for the auscultation on concrete dams, and the primary types of deterioration of concrete dams. According to the author, the multiple extensometer for example, is related to the monitoring of deteriorations caused by sliding, different declinations, land subsidence of the upstream base, and the Alkali-Aggregate Reactivity.

84 Multivariate Analysis in Management, Engineering and the Sciences

slipping (a) and the overturning (b) are emphasized.

the instrumentation data can reveal a critical condition.

involve the construction.

dam, and instrumentation can identify some of these changes.

making the water of the reservoir to try passing through upstream in order to archive a hydraulic equilibrium. To do so, the water percolates through the foundation mass of the dam. During this process, the infiltrated water generates vertical forces acting upward over the dam, these forces are called uplift pressure in dam. The resultant of these forces is represented by Fuplift. Furthermore, the water from the reservoir generates horizontal forces that act downstream-upstream over the dam. These forces are called hydrostatic pressures against the dam wall. The resultants of these forces are represented by Freservoir. These two resultant forces are called destabilizing forces. As for the force P (dam weight) it is a stabilizing structure force. The combination of Fuplift and Freservoir can cause the overturning and the slipping of the dam, not just because of the efforts and moment when it is directly applied, but also for the relief of the weight of the structure itself (in case of uplift pressure). The above described effects of loads on dams can be observed on figure 1, where the

The loading conditions and the properties of materials can change over the lifecycle of a

Figure 2 shows the differences in the behavior of the dam in relation to summer and winter climate conditions, as well as its consequences. In summer, an expansion of the concrete occurs, and that causes the block to tumble downstream. This overturning causes the block to compress the foundation. In winter, the concrete is compressed causing the block to tumble upstream, returning to initial position. As a consequence the pressure that occurs in summer over the foundation to be relieved. In this way, it is possible to identify a cyclical behavior of the structure, intrinsically conditioned by the environmental conditions which

**Figure 2.** Behavior of the dam in relation to summer and winter climate conditions (Adapted from [8]).

According to [9], the instrumentation must be used as supplement to visual inspection when executing the evaluation of the performance and safety of dams. The careful inspection of The measurement of the declinations is one of the most important observations for monitoring a dam behavior during the period of construction, of dams filling and operation. The measurement of the declination can be performed through a multiple point rod extensometer installed on boreholes [10]. Figure 3 shows the multiple point rod extensometer and an example of a typical profile of a multiple point rod extensometer at *Itaipu*.

**Figure 3.** Multiple point rod extensometer and a example of a typical profile of a multiple point rod extensometer at *Itaipu* (Adapted from [11]).

The measurements of displacements and deformation can be performed in several parts of the foundation with the usage of various rods. Among these displacement and deformations are the contact of concrete and rock, joints and faults and other sub-horizontal discontinuities in the foundation. This approach was used at the Itaipu Dam, where different points of foundation mass were instrumented, specially the geological discontinuities. Figure 4 shows a typical geological profile of the foundation mass of the Itaipu Dam part, which has no tunnel in its right-side, where primary geological discontinuities can be found (contacts, joints, and gaps) of that specific site. In blocks where there is a transversal gallery access to the shaft, the installation of downstream-upstream extensometers can help in the measurement of the angular displacement of the dam with the foundation [10].

Itaipu Hydroelectric Power Plant Structural Geotechnical Instrumentation

Temporal Data Under the Application of Multivariate Analysis – Grouping and Ranking Techniques 87

The Itaipu Binacional, the largest energy producer of the world, had its construction started in 1973 at a river stretch of Rio Paraná known as Itaipu, which in Tupi language means "the singing boulder", located in the heart of Latin America, on the border of Brazil and Paraguay [12]. The construction of the dam ended in 1982 and the last generator unit was

Nowadays, the Itaipu Dam has 20 generator units of 700 MW (megawatts) each, generating a total potential of 14.000 MW. Itaipu Binacional (Bi-national Itaipu) reached its record in producing energy in 2000, generating over 93,4 billions kilowatts-hour (KWh). It is responsible for supplying 95% of the energy consumed in Paraguay and 24% of all the

The Itaipu Dam has 7.919m of extension and a maximum high of 196m; these dimensions made of the Itaipu construction a reference in concrete, and dam safety studies. Itaipu dam is made of two stretches of earth dam, one stretch of rock-fill dams and concrete stretches, and these forms the higher structures of it. Figure 5 illustrates the whole structure of the Itaipu dam, and table 1 shows the main characteristics of the stretches pointed on figure 5.

It is possible to find in all the Itaipu extension an amount of 2.218 instruments (1.362 in the concrete, and 865 in the foundations and earthen embankments) and from this amount 270 of them are automated, to monitor the performance of the concrete structures and foundations. Furthermore, there are 5.239 drains (949 in the concrete and 4.290 in the foundations). The readings of these instruments occur in different frequencies, they can be, for example, daily, weekly, fortnightly, and monthly, depending on the type of instrument.

Even though, every stretch of the dam is instrumented and monitored, one of the stretches, called *Barragem principal* (main dam) (Denominated stretch F and identified as number "5"

**4. Research course** 

**4.1. Itaipu Binacional** 

completed in 2008.

Brazilian consumption.

**Figure 5.** Whole structure of the Itaipu Complex [12].

These readings have been stored for over 30 years.

**Figure 4.** Schematic geological profile of the foundation of Itaipu (ITAIPU BINACIONAL, 1995, *apud* [8]).

The measurement of the horizontal displacement of the ridge is a relevant parameter which is affected by deflections of the concrete structure, by the rotation of the base of the structure (due to the deformability of the foundation), and by thermal and environmental influences. These displacements are affected by the characteristics of the concrete or by the proprieties of the foundation rock mass, resulting in important information for the auscultation of the behavior of the dam and of its foundation. The horizontal displacements of the ridge can be measured by a direct pendulum, usually installed at the end of the construction process. The measurements are done on the stages of reservoir spillway and of dam operation [10].

The stability of the structure in terms of sliding, overturning or floating is directly affected by the level of the piezometric pressures in the concrete-rock interface and in the sub horizontal discontinuities of low resistance that exists in the foundation. The measurements of low pressures on the concrete dam foundation are important for the monitoring of its safety conditions. The drainage is one of the most efficient ways to ensure adequate safety coefficients. The measurements of low pressure are performed by the piezometer [10].
