Scale Modeling of Beni Slimane Dam

Danica Starinac1, Predrag Vojt1, Marijana Damnjanović1, Dragiša Žugić1, Radomir Kapor2, Ljubodrag Savić2, Budo Zindović2, Predrag Đajić3

 

1 Jaroslav Černi Institute for the Development of Water Resources, Jaroslava Černog 80, 11226 Pinosava-Belgrade, Serbia; E-Mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

2 University of Belgrade - Faculty of Civil Engineering, Bulevar Kralja Aleksandra 73, 11000 Belgrade, Serbia

3 Energoprojekt Hidroinženjering Plc, Bulevar Mihaila Pupina 12, 11070 Belgrade, Serbia

 

Abstract

The design of the Beni Slimane Dam (Medea Province, Algeria) has been verified by scale model analyses, conducted on two separate physical models – the partial model of the labyrinth spillway and the complete model of flood evacuation structures. This paper describes the analyses carried out on the complete model, scaled 1:30. The initial design of the chute and stilling basin was optimized on the basis of model testing. Tests carried out on the scale model with a movable bottom (river bed) were very helpful for the design of downstream erosion protection.

Keywords: scale model, full model, labyrinth spillway, Beni Slimane.

 

Introduction

 

A labyrinth spillway is a hydraulic structure devised as a result of the aspiration to design the largest possible spillway-crest length and ensure the highest possible spillway capacity. The labyrinth spillway can be a very economical solution, given that it provides a higher discharge rate for the same total head, compared to conventional straight overflow weirs and ogee crest spillways (Hepler, 1992).

Labyrinth spillways first came into use some 30 years ago (Hepler, 1992; Vischer and Hager, 1999). Although labyrinth spillway research (Tullis et al., 1995; Tullis et al., 2007; Khode et al., 2010) has intensified since then, the amount of experimental data is still limited and empirical formulas proposed in the literature need to be applied with due caution. Each new labyrinth spillway is a unique structure, such that scale models are recommended to assess the design.

This paper presents the results of model tests of Beni Slimane Dam, conducted at the Hydraulics Laboratory of the Jaroslav Černi Institute (Starinac, 2014).

 

Beni Slimane Dam overview

Beni Slimane Dam is being built across the Mellah River, some 7 km south of the City of Beni Slimane (Medea Province, Algeria). The main functions of the dam are to regulate the discharge of the Mellah River and provide irrigation water supply. Additionally, the dam and its appurtenances need to ensure a safe discharge of Q = 563.4 m³/s, which is equivalent to a 10,000-year flood.

The dam will create a reservoir with a full reservoir level (FRL) at 715.00 m above sea level. The design calls for a zoned earth dam, with a clay core (Figure 1). The dam crest has been set at an elevation of 719.00 m.a.s.l. The width of the crest is 11.00 m and the length about 279 m. The slope of the upstream face is 1V:3H, and of the downstream face 1V:2.75H. The maximum structural height of the dam is 67 m.

The spillway structures are located at the right dam abutment. They comprise a labyrinth spillway, chute and stilling basin.

The cross-sectional width of the labyrinth spillway is 32 m (center line). It is comprised of three segments, whose side legs are at an angle of 19° relative to the spillway axis. The total length of the crest is 77.1 m. There is a bridge structure above the spillway. Side walls are provided to direct the flow from the reservoir to the spillway, as well as to protect the earth dam. The distance between the side walls gradually reduces in the direction of the flow. The bottom of the spillway is horizontal (at 711.00 m.a.s.l.) and the height is 4 m, such that the crest elevation is 715.00 m.a.s.l.

The spillway structure extends into a chute whose length is 190 m, width 12 m and slope 34.4%.

In the downstream section, the chute gradually expands over a distance of some 40 m, from the initial 12 m to 20 m, which is the width of the stilling basin. The length of the stilling basin is 50 m and its bottom elevation 646.8 m.a.s.l. It has been designed as an USBR II type structure.

Given the complex hydraulic conditions associated with a labyrinth spillway, as well as the fact that the Beni Slimane project is highly specific, scale model testing was conducted for the purposes of the final design.