Typical Dams Research Articles

Safety and stability evaluation of the uranium tailings impoundment dam: Based on the improved AHP-cloud model

To solve the problem of safety and stability of the uranium tailings impoundment dam, based on the whole process of emergency management, the safety and stability evaluation system of the uranium tailings impoundment dam is established by using analytic hierarchy process (AHP) from the four aspects of design and construction, natural environment, operational stability and management, and the general weight of each evaluation index is calculated; the improved AHP-cloud model is introduced to obtain the basic evaluation cloud map for the safety and stability of the uranium tailing dam and two typical dams were evaluated in a large uranium tailings impoundment in southern China. The results show that the model can produce a more accurate evaluation of the safety and stability of the uranium tailings impoundment dam, and provide a reference for the subsequent decommissioning management work.

Study on Stability Reduction Characteristics of Earth and Rockfill Dams under Rapid Drawdown Using Fully Coupled Seepage-Stress Analysis

It can be a great expense to examine individually the stability of earth and rockfill dams on rapid drawdown in civil engineering practice. The aim of this present work is to clarify the safe type on the rapid drawdown among the most common types of earth and rockfill dams and to introduce cheaply the types in dam design. First, a transient analysis of saturated-unsaturated seepage coupled with stress is carried out in the cross sections of typical earth and rockfill dams the during rapid drawdown, and the safety factors of the upstream slopes are determined by the shear strength reduction method. Then, the typical dams are compared for the stability characteristics so that designers can select the safe type of earth and rockfill dams on rapid drawdown. The obtained results show that the decreasing rate of safety factor in a central core dam is 0.72–0.85 times than one of the homogeneous dams and 0.17–0.40 times than one of the sloping upstream core dams so that it is more stable than other earth and rockfill dams during rapid drawdown.

Influence of the Mechanical Properties of Masonry in the Structural Behavior of Gravity Dams

ABSTRACT In this paper, the influence of the mechanical properties of masonry in the structural behavior of old masonry dams in Mexico is evaluated. Mexico has an important number of masonry dams, which were constructed from seventeenth century to nineteenth century and continue to operate until now. Two different typologies of typical dams in Mexico were analyzed. The first typology corresponds to a dam with inclined faces (upstream and downstream) and the second one corresponds to a dam with a vertical face upstream and an inclined face downstream. The selected dams were analyzed by traditional methods, where the resultant of all forces acting on the dam must lie in the third middle of the base and the hypothesis of no tension material is assumed. Sometimes, this approach is too conservative and mostly does not reflect the real structural behavior of the dam. Thus, 2D models of both dams by means of a semi–discrete approach were performed. Considering the non-linear behavior a parametric study was made in order to identify the mechanical properties that have more influence on the structural behavior. Parametric analyses show that the tensile strength of the masonry is the property of greater influence on the structural behavior.

A Modified Newmark Methodology for Permanent Deformation Analysis of Rock-Fill Dams

Newmark sliding block approach has been extensively studied by many researchers in the past decades. Significant progress has been made to alleviate its deficiencies and overcome its simplifying assumptions, but some aspects such as the cyclic shear strength and time history vertical acceleration in the Newmark sliding displacement analysis are seldom considered strictly. In the presented research, a modified Newmark methodology for sliding deformation analysis of rock-fill dams subjected to strong earthquake is proposed. In order to make the seismic safety evaluation of dams more realistic, the influence of cyclic shear strength (earthquake-induced reduction of shear strength) and time history vertical acceleration obtained from the dynamic response analysis on the critical acceleration and accumulative sliding displacement of the flexible sliding body is considered. Detailed comparison between the proposed method and existing methods is performed via the analysis of two typical dams, that is, a virtual rock-fill dam with a height of 100 m which is assumed to be situated on rock formation and a real core rock-fill dam with a height of 150 m built on deep overburden layers. It is demonstrated that the cyclic shear strength and time history vertical acceleration within flexible sliding body, as highlighted in the proposed method, have significant effect on the seismic safety evaluation, critical acceleration, and accumulation of sliding deformation of rock-fill dams subjected to strong earthquake loading. The existing approaches tend to provide unconservative evaluation on the consequences of earthquakes on rock-fill dams.

Seasonal Thermal Displacements of Gravity Dams Located in Northern Regions

Seasonal temperature displacements are an important component of the total displacements recorded by pendulum measurements at gravity dams located in northern regions. A hybrid dam displacement model is presented in this paper to interpret these displacements and extrapolate the response for an extreme thermal event not yet experienced by the dam. The hybrid model uses a simplified deterministic structural dam representation with beam elements in complement to a hydrostatic seasonal time (HST) statistical displacement model. Comparisons are first established between 1D heat transfer analyses of typical gravity dam sections, and 2D finite-element (FE) analyses. Thermomechanical displacements are compared to show the validity of the proposed simplified deterministic beam model for typical dams. A case study of an actual 40 m gravity dam located in Quebec, Canada is then presented. It is shown that the deterministic model can be calibrated using the pendulum displacements and the HST model. The calibrated deterministic model is then used to extrapolate the displacement response for extreme thermal events not yet experienced by the dam. The proposed methodology represents a simple extension of the gravity method, widely used to verify gravity dam stability, as a first step to interpret recorded pendulum displacements and set appropriate warning and alarm levels on a rational basis before developing 2D and 3D thermomechanical FE deterministic dam models that require a lot of resources and expertise to be used effectively.