Abstract

Arch dams have different properties that play a relevant role in their behavior, although it is not clear to what degree or in what sense. There is some consensus regarding the relevance of certain factors such as length at crown, height, base and crest thickness, or Young modulus of dam and foundation. However, others such as the shape of arcs and cantilevers, which are correlated and whose effect is more difficult to consider, can also be influential. In this work, a systematic study of the response of arch dams in front of the common loading scenarios has been carried out, taking into account the usual range of variation of their properties. In total, 39 input variables related to geometry, material strength and thermal load were considered. Ranges of variation for each of these parameters have been defined according to the usual design criteria and 3,000 different geometries – together with the corresponding FEM models have been generated with random values of these parameters. The resulting displacements and stresses have been used to fit prediction models based on a machine learning technique named ‘random forests’ that give an estimate of the dam response. The interpretation of these models can be associated with the relative importance of the characteristics of arch dams on each of the behavior variables.

Abstract

Double curvature arch dams feature geometrical complexity with a significant amount of parameters involved. Different criteria exist to assist in the design task, from simplified geometrical approaches to optimization procedures. However, most of them present a lack of flexibility and are not integrated in computer-aided design tools. In this contribution, an interactive and flexible software tool is presented to support the complete design process: geometrical definition, FEM model generation (including the mesh, the loads and the boundary conditions) and thermo-mechanical analysis. The design can be performed with different levels of detail to adapt to the information available in each stage of the project. The tool allows defining the shape of the reference cylinder, the excavation depth and slope along the foundation, the crown cantilever thickness and curvature, the shape and location of horizontal arcs; all these steps were described in former contributions. Here, special attention is paid to the introduction of additional features such as joints, spillways, abutments of varying shape and outlet works. All steps have been defined with a high degree of flexibility in the design process. The tool is integrated with the pre and post process software GiD, which allows taking advantage of its functionalities, such as mesh generation and results analysis. It is also coupled with a specific application for thermo-mechanical analysis of dams, developed in Kratos Multiphysics – a framework for building parallel multi-disciplinary simulation software. The whole design process can be followed in a unique environment, because the structural response of preliminary designs can be computed and the results considered to refine the dam geometry.

Abstract

Landslides in reservoirs constitute one of the main threats to dams. Although they are not frequent, they may generate severe damages in the population and goods placed near the shores. It is a complex phenomenon, because of the interaction between the landslide, the still water in the reservoir, and the dam. The Particle Finite Element Method (PFEM) is an innovative numerical scheme which combines a lagrangian approach with the resolution of FEM equations via mesh generation. In previous works, it had been applied to the simulation of landslides in reservoirs, considering the moving body either as a rigid solid or as a Newtonian fluid. Despite the promising results of the simulation of some reference cases, these constitutive models showed poor performance when applied to other relevant events, such as Vaiont case. Current work introduces the implementation of a non Newtonian Bingham model in the particle finite element method scheme, and the results of its application to several benchmark cases. Some of them have been used to calibrate the parameters of the Bingham model, whereas others served as test cases. The phenomenon presents several intrinsic uncertainties, such as the lack of precise information about the physical properties of the landslide, its geometry, its granulometry, the drag coefficient along the sliding surface, among others. In spite of that, results show that the Bingham model implemented can be useful for estimating the potential consequences of landslides in reservoirs. This implementation makes the PFEM a versatile numerical tool for the analysis of landslides in reservoirs, provided that from now on both rigid solids, Newtonian and non Newtonian fluids can be accounted for. The authors are currently working in the optimization of the numerical code, so that more complex problems could be afforded in more detail. In addition, the erosion module is being validated, in order to reproduce effects such as the dragging of the underlying material due to the landslide, as well as the effect of overtopping on dam stability, particularly for rockfill dams.

Abstract

The static and seismic analysis of Janneh arch-gravity dam (157 m) is carried out by considering a combination of self-weight, hydrostatic, uplift and seismic loads. Linear and nonlinear analyses are performed for both static and seismic cases. Nonlinear behavior is studied by means of joint elements in the contact between the rock foundation and the dam following a bilinear cohesive law. The hydrodynamic effects derived to seismic loads are also considered. Hydrodynamic Westergaard’s approach is applied in the pseudo-static analysis, and the Westergaard’s generalized added mass is used for time-history case.

Abstract

The paper presents an overview on the computational tools developed in CIMNE for the analysis of the behavior of rockfill dams in overtopping scenarios, as well as for the design of protections systems against overtopping. In this latter case two different applications are presented: the design tool for a wedge shaped blocks (WSB) shoulder protection and the computational models for the analysis of the hydraulic performance of highly convergent spillways. Advanced finite element techniques are combined with particle techniques and artificial neural networks in the framework of the Kratos Multiphysics for reaching the optimal solution procedure for any of the above mentioned problems. An extensive validation is carried out using experimental data provided by the SERPA group of the Technical University of Madrid.

Abstract

The article summarizes the research studies performed by the Research Group on Dam Safety (SERPA) of the Technical University of Madrid and the International Center for Numerical Methods in Engineering (CIMNE) in collaboration with the company PREHORQUISA. Such studies aim to deepen on the theoretical and practical understanding of wedge shaped blocks (WSB) technology. This research was funded by the Spanish Ministry of Economy and Competitiveness through the research projects called ACUÑA (IPT-2011-0997-020000) and DIABLO (RTC-2014-2081-5). One of the projects goals was to develop a new model of WSB looking for improving the performance of the existing ones. This research led to the new model of WSB called ACUÑA, proprietary in Spain since May 2017 (ES2595852). The paper presents a comparison between the behaviour of the new block with one of the existing models, specifically Armorwedge^TM. Such comparison has been made using physical and numerical modelling, studying the hydrodynamic pressures on the block and the leakage flow through the joints between blocks and the aeration vents

Abstract

A finite element thermomechanical analysis of a concrete arch dam has been carried out to predict the extent of cracking due to temperature variations. A linear elastic analysis allows us to find out the areas exceeding the tensile strength of the concrete. Then, a smeared crack approach based on a non-local damage model is used to accurately predict the pattern of the damage at the dam. Additionally, joint elements are introduced in the damaged regions of the wall to analyze the evolution of the crack aperture over the year.

Abstract

Double-curvaturedamsareunique structures for several reasons. Their behaviour changes significantly after joint grouting, when they turn from a set of independent cantilevers into a monolithic structure with arch effect. The construction process has a relevant influence on the stress state, due to the way in which self-weight loads are transmitted, and to the effect on the dissipation of the hydration heat. Temperature variations in the dam body with respect to those existing at joint grouting generate thermal stresses that may be important in the stress state of the structure. It is thus essential to have a realistic estimate of this thermal field, also called reference or

Abstract

This paper is aimed to analyze how a bibliographic work should be considered not as rigid collection of publications but as an opportunity to discover knowledge which often turns into the development of new technical ideas and finally it translates into innovation.

Abstract

La Baells arch dam has a height above the foundations of 102 m. It entered service in 1976 and since then it had correct performance, which has been controlled with a very complete monitoring system and conventional interpretation techniques. This communication presents the results of a pilot study in which machine learning techniques have been applied to analyze their monitoring data. These techniques offer greater flexibility than conventional procedures for generating dam response prediction models, as well as for identifying relationships between devices of a different nature. This allows a better understanding of the behavior of the structure and greater safety control.