Experimental and numerical seismic investigations of the Three Gorges dam

doi:10.1016/j.engstruct.2004.11.009

Engineering Structures

Volume 27, Issue 4, March 2005, Pages 501-513

https://doi.org/10.1016/j.engstruct.2004.11.009 Get rights and content

Abstract

The Three Gorges dam project in China is the largest water conservancy project ever built in the world and is also currently the world’s largest construction project [China Yangtze Three Gorges Project Cooperation. A brief introduction on the Three Gorges project on the Yangtze River; 1999. http://www.nickdw.com/3-gorges/DOCS/1999.htm]. A seismic analysis of the powerhouse monolith of the Three Gorges dam is performed through model testing at a geometric scale of 1:100 on a shaking table and numerical simulation using a three-dimensional finite element model of the structure. It is observed from this combined experimental and numerical study that the powerhouse monolith has a relatively high capability for earthquake resistance and satisfies the seismic design requirements of the national code of China [Ministry of Hydraulics and Hydroelectrics. National standard of the People’s Republic of China SDJ10-78: seismic design code of hydraulic structures; 1978]. This study also shows that the seismic responses calculated from the three-dimensional finite element model are in good agreement with those obtained from the model test on the shaking table for the case of an empty reservoir and rigid foundation. The outcome of this study should be of interest and use to professionals involved in the design of large gravity dams.

Introduction

The Yangtze river is the longest river in China. Its length and its average runoff are both ranked number three in the world. The Three Gorges project is the greatest dam project ever planned and is also currently the largest construction project in the world. It includes the gravity dam, spillway structures, powerhouses, and navigation structures, as shown in Fig. 1 [1]. The dam is a concrete gravity dam. This type of structure has a main feature of a high level of safety and a good capacity for earthquake resistance. Many of the technical parameters of the dam are ranked number one in the world. The Three Gorges dam, which has been attracting worldwide attention, is located at Sandouping, Yichang, Hubei Province [1]. Its downstream area is the most developed region in China; therefore, its level of safety has the utmost importance for both political and economical reasons. The dam is 3035 m long on the top, with the crest at EL 185 m [1]. The width of each dam monolith is 25 m. The diameter of the penstock at the powerhouse monolith under consideration in this study is 12.4 m, approximately half of the width of the powerhouse monolith. This reduces the stiffness of the dam body significantly and also has a great influence on the dynamic characteristics and response of the dam. The penstock uses a semi-buried back conduit in the downstream slope of the dam. This is a relatively new structural form. It is noted that few studies have been carried out to investigate the behavior of this type of structure in the past; therefore, many technical problems involved in the design and construction need further and detailed investigations. As the structural design of this huge dam is very complicated, in order to ensure its safety, many research works are required. On the basis of the existing information obtained in the design stage of this dam, the seismic response of the powerhouse monolith of the dam is analyzed and presented in this paper. A three-dimensional finite element model of the powerhouse monolith is established and a dynamic analysis is conducted numerically. Meanwhile, a model test of the powerhouse monolith at a geometric scale of 1:100 is carried out on a shaking table to investigate the seismic response of the structure. In addition, a comparison between the test results obtained from the shaking table and those from the finite element seismic analysis is made for the case of an empty reservoir and rigid foundation. The outcome of this study should be of interest and use to professionals involved in the design of large dams.

Evaluation of seismic effects on large dams is very important and a challenging task. Wieland [3] presented a comprehensive overview of seismic aspects of dams. Thus, only some previous works that are directly related to the present study are mentioned below. There has been no major failure or collapse reported for large concrete dams in seismic events. However, there have been some structural damage cases caused by earthquakes. For example, these include the earthquake damage of the Hsinfengkiang buttress dam in China during the 1962 Heyuan earthquake in China [4], the Koyna gravity dam during the 1967 Koyna earthquake in India [5], and the Sefid Rud buttress dam during the 1990 Manjil earthquake in Iran [3]. The earthquake damage of the Koyna gravity dam has been studied extensively. Chopra and Chakrabarti [5] reviewed the earthquake experience at the Koyna dam. Although there was no collapse, a long crack occurred at the sharply turning section near the top. Dynamic analysis [6] revealed that for the Koyna dam, in the recorded motion, the tension stresses near the section of sudden change of cross-section were much larger than the tensile strength of concrete. Oberti and Lauletta [7] and Niwa and Clough [8] conducted model tests using shaking tables and obtained many valuable results. Ghobarah and Ghaemina [9] carried out a small scale dam model test with simulated dynamic forces for earthquake-resistant design of a dam. Riyaz and Taylor [10] conducted destruction tests on a concrete gravity dam. Yoshida and Baba [11] studied the earthquake-resistance capacity of dam structures. Araujo and Awruch [12] used a probabilistic finite element method for the analysis of a concrete gravity dam. Ghaemina and Ghobarah [13] studied the nonlinear seismic response of concrete gravity dams considering the interaction of the dam and reservoir. Fenves and Chopra [14] presented a simplified approach for the analysis of concrete gravity dams under earthquake actions. For the Three Gorges dam project, extensive studies on many aspects related to the design and construction of the dam have been conducted by various institutions in China over the last few decades. For the design and analysis of the powerhouse monolith, Wu and Ma [15] conducted numerical static analysis of the powerhouse monolith of the dam; Xu [16] performed three-dimensional dynamic analysis of the powerhouse monolith using a finite element method; Li and Li [17] investigated the seismic responses and dynamic reliability of the powerhouse monolith using the response spectrum method. However, detailed information on the earthquake-resistance capacity of the dam has rarely been reported internationally. Therefore, a combined experimental and numerical study on the seismic responses of the powerhouse monolith of the Three Gorges dam is conducted, and some representative results are presented and discussed in this paper.

Section snippets

General introduction of the powerhouse monolith of the dam

Fig. 2 shows a sketch of the powerhouse monolith of the Three Gorges dam. The penstock is located at the powerhouse monolith of the Three Gorges dam. The height of the top and the base of the dam monolith are EL 185 m and EL 27 m, respectively. The designed normal pool level of the reservoir is EL 180.4 m. The width of the dam monolith is 25 m. Along the stream direction, the length of the dam at the top of the dam is 25 m and at its base is 118 m. The static elastic modulus of the concrete of

The model test

The seismic model test of the powerhouse monolith of the Three Gorges dam consists mainly of the following procedures: (1) design and construction of the model; (2) determination and simulation of the boundary conditions; (3) evaluation of the dynamic characteristics of the model; (4) conducting of the model test on a shaking table; and (5) analysis of the experimental results.

Seismic analysis using the finite element method

In seismic analysis of dam structures, the loading conditions are relatively complicated. During an earthquake, the vibration of a dam will induce vibration of the water in the reservoir, and then the dynamic water pressure will be acting on the dam. Therefore, the interactions of the dam and water in the reservoir, and their effects on the vibration, stress, and strain of the dam, should be considered. However, these interactions are very difficult to simulate in model tests on shaking tables;

Conclusions

A combined experimental and numerical study on the dynamic characteristics and seismic responses of the powerhouse monolith of the Three Gorges dam was conducted in this paper. Specifically, in the model test, the experiment was carried out on a shaking table. In the numerical analysis, the powerhouse monolith of the dam was analyzed by a finite element method. It was found that the data measured from the model test were in satisfactory agreement with the calculated results for the case of an

Acknowledgements

The authors are grateful to the reviewers for their very useful comments and suggestions. The support provided by the Yangtze River Water Resources Commission of China for this study is gratefully acknowledged. The work described in this paper was partially supported by a grant from the Research Grant Council of Hong Kong Special Administrative Region, China (Project No CityU 1131/00E).

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Experimental and numerical seismic investigations of the Three Gorges dam

Abstract

Introduction

Section snippets

General introduction of the powerhouse monolith of the dam

The model test

Seismic analysis using the finite element method

Conclusions

Acknowledgements

Advances in Engineering Software

Earthquake engineering

The earthquake experience at Koyna dam and stresses in concrete gravity dams

Earthquake Engineering and Structural Dynamics

Earthquake resistant design of concrete gravity dams

Journal of Structural Division, ASCE

Experimental study of small scale dam models

Journal of Engineering Mechanics, ASCE