Passion for Progress... and Progress in Water Resource Development

Transcription

1 BAUER on Large Dams

2 Passion for Progress... and Progress in Water Resource Development Based on experience of more than fifty years BAUER Spezial tiefbau GmbH as the parent company within the BAUER Group, evolved into one of the largest and most respected specialist foundation organizations which provides excellent service, equipment and innovation in ground engineering techniques necessary for Dam construction. The strength of our company are In-house resources facilitating world-class solutions to projects around the globe with the goal to deliver safely, on time, on budget and with no surprise.

3 Contents 4 "Bauer on large Dams" Worldwide Hinze Dam Upgrade, Australia Merowe Dam, Su dan Péribonka Hydroelectric Development, Canada The "Naga Hammadi Barrage", Egypt 9 Bauer s Contribution to make your Water Resource Development feasible The Cut-Off Wall The See page Barrier Greenfield Projects Design and Construction Upgrade, Rehabilitation and Repair Projects 10 Bauer Quality and Safety Strategy Ground Pre-Treatment The continuous Seepage Barrier 11 Bauer Equipment and Technique

4 4 WORLDWIDE Hinze Dam Upgrade The Hinze Dam is located on the Nerang River, 15 km southwest of Nerang in South East Queensland. It provides the major part of the water supply for the Gold Coast region. The first construction of the Hinze Dam Cutter HTS 65 was made in The raise during the second stage was in 1985 up to a level of 93.5 meters. During Stage 3 the dam will be raised by 15 meters to approximately 108 meters and will double up the water capacity. The upgrade will provide an additional 79,000 million litres of flood storage capacity and increase the dam s yield by at least an additional 16 million litres a day. The project will also provide greater flood mitigation for properties downstream of the dam and will make the structure compliant with current dam safety design guidelines and standards. Within the Hinze Dam upgrade design stage the permeability on the dam and the foundation was evaluated. It was found that the increased water pressure has an impact on the right abutment, due to the presence of highly permeable chert and greenstone, greywacke with a discrete series of defects as well as continuous defects in geological contact zones. This unfavourable geological formation influences the seepage through the structure, which causes increased leakage through the foundation, internal erosion and piping. Cut-Off wall Panel The design team concluded that only a plastic concrete wall which cuts off the seepage through the hard rock strata (UCS up to 150 MPa) will meet all the requirements providing a reliable, sustainable seepage barrier. The Cut-Off wall of 220 m length, up to 50 m deep and 0.8 m thick constructed by Bauer begins within the existing saddle dam, extends through the section of the central core and keys into a 5,000 m² hard bedrock area below the core where seepage will be decreased to its minimum. Cut-Off wall by Bauer Cutter and Clamshell

5 WORLDWIDE 5 Merowe Dam The Merowe Dam is designed to serve several purposes, namely: the generation of electricity from its 1,250 MW hydropower station; the development of centralized agricultural irrigation schemes (about 300,000 ha) and the protection of the Northern State against devastating high floods of the river Nile. The Dam is located at the fourth cataract on the River Nile at Merowe. The project has a high priority in the National Comprehensive Strategy, because the country is suffering from an acute shortage of electricity power, which impedes the economical and social development. The main dam of the Merowe project is a classic earth core rock fill dam (ECRD) with a central earth core, fine and coarse filters and upstream and down - stream rock fill shoulders with a total length of 883 m and a height of 64 m. The ECRD is founded on alluvial sediments, which are up of 30 m thick. To control seepage below the dams' clay core, Bauer installed an approx. 400 m long, 1.2 m thick plastic concrete Cut-Off wall down to 64 m, which penetrates about 4 m into very hard bed rock (up to 110 MPa UCS). On top of the Cut-Off wall a cushion of highly plastic material is provided to avoid stress concentrations in the wall and cracking of the core. Cross View Cut-Off Wall Dam internals e. g. spillway, stilling basin and many other structures are built with Bauer bored piles and secant pile walls. Cut-Off wall by Bauer Cutter and Clamshell Bored Pile and Secant Pile Wall Installation by Bauer BG Drill Rigs

6 6 Cutter CBC 135

7 WORLDWIDE 7 Péribonka Hydroelectric Development The Péribonka dam is located in the heart of the province of Québec, Canada. The project involves the construction of a main earth dam across a main and secondary valley, two main dikes and a hydroelectric generating Run-Of-River station with an estimated capacity of 385 megawatts. Under the main dam body, the construction of an exceptionally deep Cut-Off wall was required, to create a seepage barrier in highly permeable riverbed alluvia. Bauer was awarded the contract on the basis of an alternative design: the plastic concrete Cut-Off wall to be completely embedded in the bedrock, a design which avoided any potentially hazardous area to be sealed by cement grouting. The Cut-Off wall was exceptional by its depth, reaching almost 116 m, and being surrounded by complex geotech nical ground conditions. Bauer commissioned a hydraulic cutter, the CBS CBC 135, the biggest ever manufactured, which included new features and was designed specifi cally for the construction of the Péribonka dam Cut-Off wall. Beside the extreme depth of the bed rock, the design was further complicated by the presence of hard rock including granite, with strength sometimes in excess of 200 MPa, quasi vertical rock cliffs, rock overhangs, and gullies filled with coarse alluvia, including boulders. In addition to the Cut-Off wall construction Bauer provided a complete construction package comprising soil improvement of alluvium and manmade fill material by vibro densification down to depths of 48 m rock consoli - dation and contact grouting as well as Deep Vibrator construction of a grout curtain to depths of up to 150 m by drilling and grouting; and the installation of permanent and temporary dewatering systems. With the plastic Cut-Off wall construct - ed in Péribonka, the technique has Drilling and Grouting Works proven to provide solutions for dams in ground conditions which are beyond the limits of other techniques such as cement grouted cut-offs. Glacial Gully 0 10 m 20 m 30 m 40 m 50 m 60 m 70 m 80 m 90 m 100 m 110 m 120 m Original proposal Cut-off Wall combinedwith Cement Grouting approx. 50 m alluvium medium size boulders boulders up to 4 m Bauer's proposal Cut-off Wall fully embedded in rock Earthworks Water Well Installation by Bauer BG Drill Rigs Drilling and Grouting with Bauer small diameter drill rigs and Bauer batching and pumping plants Soilimprovement with Bauer Vibroflotation System Cut-Off wall by Bauer Cutter and Clamshell

8 1 : 15 1 : WORLDWIDE Naga Hammadi Barrage The old Naga Hammadi Barrage, one of three structures constructed between 1900 and 1930 along the River Nile in Upper Egypt, is located 130 km north of the city of Luxor and 360 km downstream of the Aswan Dam. The reservoir feeds an agricultural irrigation system of 320,000 ha year-round. A conceptual study comparing rehabilitation of the existing barrage versus the construction of a new barrage concluded that a new 330 m long sevengate dam, raising the water level up to 8 m, for irrigation should be built along with a ship lock and a 64 MW Run-Of- River hydropower plant. This was considered the most economic alternative for which geologically favourable conditions were identified 3 km downstream of the existing barrage. The study of the alternatives involved a variety of complex and technically challenging tasks, including 3-D mathematical modelling of groundwater flows, physical hydraulic model tests, Well installation optimisation calculations, comparison of flood protection concepts and a comprehensive environmental impact assessment for the project. To facilitate the construction of the multipurpose barrage, Bauer installed the seepage barrier consisting of a plastic concrete Cut-Off wall with a depth down to 60 m. The wall toe is embedded into a silt/clay layer and provides an excellent impervious cut-off, which enabled the excavation of the large temporary construction pit down to 30 m below river level. Bauer installed several water wells for the dewatering of the construction pit. The Cut-Off wall is approx. 1,800 m long and occupies an area of approx. 243,000 m². Cut-Off wall by Bauer Cutter and Clamshell Water Well Installation by Bauer BG Drill Rigs Cut-Off wall Turbines Weir Locks Project Lay-out Cut-Off wall installation Well installation Construction Stage 1 Dewatering Excavation Buildings Construction Stage 2

9 BAUER S CONTRIBUTION 9 Cut-Off Wall The Seepage Barrier Greenfield projects Design and Construction Bauer Cut-Off Walls provide new opportunities for investors and designers involved in Water Resource Development projects. When planning a new Water Resource Development project, one of the major obstacles is finding a location with suitable geological and hydrological formations for the project, which also has appropriate environmental and social aspects. Bauer Cut-Off Walls can be installed in any type of ground condition to provide a reliable, durable and impermeable (approx. 1x10-8 m/sec.) system which ensures efficiency, durability, stability and safety for your project. Thus, the Bauer Cut-Off Wall makes selection of the project site one step easier. Bauer Cut-Off Walls convert the existing ground conditions to meet your design requirements, at a location of temporary diversion your choice. The ability to install the walls in remote areas, enables you to meet environmental and social requirements of dams. Design and Construction Stage 1 Design and Construction Stage 2 Upgrade, Rehabilitation and Repair Projects Upgrade Stage 1 As part of Dam Safety Program, Dam owners, municipal, state and private conduct regular reviews of all their dams. Although the condition of a Dam has not changed since it was built, reviews of the purpose or the design identify a need for upgrades to increase capacity or to enhance life span and dam safety which maybe compromised due to hydraulic conditions or during major earthquake. Rehabilitation Stage 1 Other existing barrier systems, for example those constructed with conventional grouting methods, often fail to meet the degree of efficiency and durability and other performance specifications over the life of the structure as required by the design. Upgrade Stage 2 Rehabilitation Stage 2

10 10 TECHNISCH KOMPETENZ Bauer Quality and Safety Strategy Based on extensive experience Bauer uses methods, equipment and techniques which allows safe construction of continuous, homogenous Cut-Off walls. Pre-Treatment Firm ground conditions are necessary in order to ensure reliable Cut-Off wall construction. Loose or soft soil layers in the dam embankment or at the foundation level or cavities in the rock may have an impact on quality and safety and therefore should be pre-treated by grouting, deep soil mixing or other soil improvement techniques. Pre-Treatment Zone Pre-Treatment Zone The goal is to create a uniform soil environment for a continuous, homogenous and safe Cut-Off wall embedment. Treatment by deep soil mixing Treatment by grouting The continuous Cut-Off wall Successful function of a Cut-Off wall depends on essential requirements: embedment continuity homogeneity Cutter Flap Control Operators Screen Therefore, the Cut-Off wall is built with overlapping primary and secondary panels using a special construction process. The main steps in Cut- Off wall construction are deep panel excavation followed by concreting. Deep excavations are done with Bauer Cutters and/or Grabs high quality maintained bentonite suspension provides efficient stability during panel excavation. Special developed electronic systems (B-Tronic) used in all Bauer machines allow the verification of the correct installation of each panel. In addition to other parameters, actual deviation and depth are shown online on a computer screen enabling the operator to control the excavation process. All parameters are recorded continuously for QA/QC purposes (B-Report). Additionally gathered data, using Inhouse 3-D-rendering tools produce a diagram showing the wall continuity. To verify panel information an ultra sonic measuring system is also used. After the excavation process is finished the bentonite suspension is displaced by concrete. In accordance with inter- 1. P 4. S national standards all plastic and/or structural concrete mixes are developed and approved in our labs and are designed by our experts. 2. P By using our professional employees on all our projects, Bauer guarantees the quality of the Bauer Cut-Off wall to meet the required specifications. 5. S 3-D-rendering of a Cut-Off wall 3. P

11 TECHNISCH KOMPETENZ 11 Bauer Equipment and Technique Cut-Off Wall Construction Technique Primary Panel cutting Primary Panel concreting Secondary Panel cutting and concreting Cutter wheels for all geological conditions for normal soil for medium hard rock for hard rock Cutting and desanding process 6 pipes Desander Mixer Pump Cutter Using the latest equipment in cutting and desanding technology, Bauer constructs Cut-Off walls also in difficult geological conditions. Mud pump

12 BAUER Spezialtiefbau GmbH BAUER-Straße Schrobenhausen, Germany Telephone: Telefax: BST@bauer.de Dam Projects Worldwide Richard Boudreau, Principal Director Production Projects, Hydro-Québec Equipment and SEBJ, about Péribonka Project "It means a lot to me to say thank you to the teams of Hydro-Québec, SNC Lavalin and Bauer. Because of the fusion of their energy, know-how and skills the works were completed in excellent quality within the given time frame. After completion of this successful phase now, we can begin with the construction of the dam so that the filling of the basin can be started as planned in autumn Congratulations!" /2011