(好资料)毕业设计-厂房设计说明书7the_2400mw_bakun_hydroelectric_project及原文复印件11页

The 2400MW Bakun hydroelectric projectWhen completed, the 2400MW Bakun project in Sarawak, Malaysia, will be the largest hydroelectric project in Southeast Asia and the biggest privatised hydropower scheme in the world. By Egon Failer and Mohd. Danel AbongProject Manager, Lahmeyer international. Lyoner Strasse 2260528 Frankfurt/Main, GermanyManaging Durectir, Bakun Managent Sdn Bhd, Wisma Ting Peh Khing, 93100 Kuvhing, Sarawak, MalaysiaThe implementation of the Bakun Hydroelectric Project was approved by the Government of Malaysia in early 1995. this huge engineering scheme will require the construction of a capacity of 2400 MW and a HVDC/HVAC power transmission system, to connect with the existing transmission networks in Sarawak and Peninsular Malaysia.The hydropower component of the project will comprise three concrete-lined diversion tunnels, a 205m high concrete face rockfill dam, a gated chute spillway and power generation facilities. The power transmission component, which will be described in a separate article, consists of two converter stations, two bipolar 500kv HVDC overhead lines and four mission capacity of 700MW and a length of some 670km each.The challenges of the Bakun HEP are not only the size and complexity of its structures and installations, but also its contracting strategy, financing, insurability and operation, especially in view of its implementation and operation within the private sector. The entire project is to be implemented on a fixed price, turnkey basis. It will be the biggest single contract ever awarded worldwide.History of the projectSarawak, one of the two Malaysian states on the island of Borneo, has the greatest hydropower potential in the country, estimated to be of the order of 20000MW.Towards the end of 1979, the German government offered technical assistance to the Malaysian authorities, resulting in the formation of the SAMA engineering consortium under the leadership of Lahmeyer Internatonal. The executing agency for Malaysia then was the Sarawak Electricity Supply Corporation(SESCO). By mid 1981, a masterplan for the optimum development of Sarawaks hydropower potential was published, identifying four major hydropower schemes-namely Bakun(2400MW), Murum(900MW), Pelagus(770MW) and Baleh(950MW). From the economic and technical points of view, Bakun was found to be the most attractive development, which was confirmed by the subsequent detailed feasibility study completed in November 1983. By end of 1987, the engineering design and associated tender documents were completed, featuring a 210m high earth-core rockfill dam with a total volume of some 28.5 million m3, an ungated spillway and power generating facilities with a total installed capacity of 2400MW. Because of the slackening Malaysian economy in the mid 1980s, the project was put on hold.Privatization and ImplementationThroughout the past eight years, Malaysia has experienced extraordinary economic growth, transforming the economy from one based on traditional agricultural and mining activities to other sectors such as manufacturing and professional services. With this booming economy and the prospect of a bright future, the demand for electricity in the country has increased at a rapid pace.With the Governments ultimate aim of becoming an industrialized nation by the year 2020 renewed interest in the advantages of the low-cost and lean power which could be generated by Bakun. Following the Governments principal policy of privatization, the Electricity Supply Act was passed in 1990 to issue licenses, regulate the operations of utilities and permit Independent Power Producers (IPPs) to generate and sell electricity in Malaysia. In 1994 Ekran Berhad was subsequently requested by the government to proceed with the development of the Bakun HEP early in 1995.Ekran Berhad, based in Sarawak and active in the construction and timber industries, issued tender documents for the river diversion works in mid-May 1995. Early in July 1995, eight tenders were received from international construction companies or consortia. The construction of the river diversion works is scheduled to commence early November 1995.After the prequalification of international construction and manufacturing consortia, modified tender documents for the main project works were issued in mid-July this year. Tender are scheduled to be received by the project developer, Ekran Berhad, in mid-January 1996. Based on financial closure no later than June 1996, the first unit will start commercial operation by mid-2002.To minimize the owners risk regarding design, construction and cost and to safeguard the financing of this huge undertaking, the entire project (including power transmission) is to be constructed under a single contract on a fixed price, turnkey basis. Value engineering is an essential contractual provision, permitting design modifications on the basis of the particular experience and working methods of civil contractors and manufacturers, thus optimizing the project as far as quality, performance, operation, maintenance and cost are concerned. The contract price will be paid according to schedules of payments.Project modificationsThe present tender design of the Bakun HEP basically follows the design concept developed in 1987, except for modifications in accordance with current hydroelectric practice and state-of-the art technology (see panel, right). Beside cost savings, the net result of these modifications will shorten the total construction period from the original 9 year and 9 months to slightly more than six years, thus improving the economic performance of the project significantly.Location and climateThe Bakun HEP is located in Central Sarawak (see Map), in the northwest region of Borneo, on the Balui River which forms the upper course of the Rajang River. The selected dam site is situated in a gorge which is up to 2km wide and 700m high, where the Balui River cuts across a prominent mountain range.The climate of Sarawak is characterized by uniformly high temperatures and humidity and abundant rainfall as a result of the influence of the North-East (November-February) and South-West (May-July) monsoons. The average annual rainfall over the catchment area is about 4500mm, and the mean annual temperature and evapotranspiration are about 25C and 1300mm, respectively.SeismicitySarawak and its adjacent areas, including the South China Sea, Brunei, Sabah and Northeast Kalimantan, are situated on a relatively stable area, located on the inner side of the active volcanic belt of Indonesis and the Philippines. Earthquakes of small to medium magnitude have been reported along Sarawaks coast from Kuching to Miri since 1870. the most intense tremor observed in Sarawak occurred on 12 February. 1994, with a magnitude located some 100km east of Sibu. However, no major structural damage was reported.Due to the insufficient number of recorded seismic events, the deterministic approach was selected to derive meaningful seismic design parameters. The highest peak ground acceleration (PGA) was derived by applying a rupture-length-magnitude-relationship developed for the Philippines and adjacent areas. A seismic potential of magnitude M-6.3 (Richter scale) was calculated, resulting in a horizontal PGA ah of about 0.12g at the site.For pseudostatic analyses, it is common practice to reduce the PGA by a factor of 1/3. However, taking into consideration the importance, size and risk class of the Bakun Hydroelectric Project (according to ICOLD Guidelines, Bulletin72 91989), horizontal and vertical accelerations of and were specified as the basic seismic design parameters for the project.Geology and engineering geologyThe rocks at the Bakun dam site are clastic sediments such as sandstones, siltstones and shales with an argillaceous or siliceous matrix. In order to gain a clear understanding of the geological conditions at the dam site, extensive geotechnical investigations were carried out during previous studies, comprising mainly the execution of:-more than 7000m of diamond core drillings;-geological surface mapping at the project site and borrow areas;-three exploration adits;-large scale rock mechanics in situ tests;-rock and soil-mechanics laboratory tests.Sandstones are the most predominant rock type (approximately 70%) in the immediate vicinity of the dam site, showing up to 100m thick massive banks. Genetically, they are greywackes consisting of angular and poorly sorted quartz and feldspar grains. Shales, which comprise the remaining 30% of the succession, are indurated claystones and are mostly silty. According to their grain size they are classified as mudstones.The geomechanical parameters of greywacke and mudstones are listed in panel, above right.Bedding is the most prominent type of discontinuity at the dam site, which orientation does not vary much. The beds strike almost perpendicular to the river valley and dip at from 60-65 in an upstream direction. The spacing of bedding planes ranges from several meters in massive greywacke and in shale to only a few millimeters in the laminated shale-siltstone sequences. The joint system ca be subdivided into two steeply inclined transverse joint sets, which strike more or less parallel to the river and a relatively flat inclined joint set which cuts the bedding almost perpendicularly.Fault zones running through either abutment of the dam were not encountered. Only minor shear zones at separations of some 10m to 30m were observed. Their thickness varies from a few centimeters to, in rare cases, 0.5m.Streamflows and floodsBased on historic streamflow and rainfall records which date back to 1962 and 1948, respectively, a long-term streamflow series was generated for the purpose of energy generation simulations, utilizing the HEC-4 multi-site, multi-variate regression model and a variable transfer function (VTF) type rainfall-runoff model.For the large catchment area of 14750km2, the longterm mean discharge at the Bakun dam site was calculated to be 1314m3/s, equivalent to a net runoff of 2810mm per year. The reconstituted streamflow series for 45 years shows a moderate variation of the average monthly streamflows from 817 m3/s in August to 1720 m3/s in December.Mainly for the design of the river diversion works, and also for the layout of the spillway and the powerhouse, a flood frequency analysis was carried out, utilizing the Extreme Value Type 1 probability distribution function. Based on 21 annual flood records, the fold frequency function.was derived, where is the return period in years.Considering economic aspects and construction constraints, floods with estimated return periods of 15 years (auxiliary cofferdam) and 500 years (main cofferdam) were selected for the design of the spillway, the probable maximum flood (PMF) with a peak reservoir inflow of 51900 m3/s was adopted.Installed capacity, power and energyThe maximum reservoir operation level of 228m as1 and the installed capacity of 2400MW were determined by detailed power system studies in 1982 and confirmed in 1994, assuming a preliminary tariff structure for the sale of energy and power.Based on the newly derived, reconstituted streamflow series over 45 years, the hydropower potential of the Bakun reservoir with its active storage volume of 19.2bn m3 was reassessed. Using continuous power (firm) as the objective function in the optimization procedure, the generation potential of the scheme was determined, the salient parameters of which are listed in panel, left.Depending upon the specific requirements of the electric grids in Peninsular Malaysia and Salawak, the power and energy to meet base, semi-base and peak demands. Furthermore, the electro-mechanical equipment is designed to provide both frequency control and spinning reserve to the grids. Besides power and energy generation, the Bakun HEP features a huge potential for flood control and will also significantly improve the navigation conditions on the Rajang River.Project layoutThe layout of the Bakun HEP is shown in Fig2, comprising the river diversion works, the concrete face rockfill dam, the spillway and power intake structure, the eight power conduits and the powerhouse.River diversion worksThe river diversion works will require the construction of three concrete lined diversion tunnels each about 1400m long, an upstream auxiliary cofferdam of same 60m height with a fuse plug arranged on the right bank, a 90m high main cofferdam subsequently integrated into the main dam and a downstream cofferdam. The diversion tunnels are located in the right abutment and run parallel to each other some 35m apart. They feature circular cross-sections with inner diameters of 12m, resulting in excavation diameters of nearly 14m. the main dimensions of the river diversion scheme such as cofferdam heights and tunnel diameters were derived form flood routing calculations utilizing the characteristics of recorded flood hydrographs. The crest levels of the upstream auxiliary cofferdam and main cofferdam were established to protect the construction site against floods with return periods of 15 years and 500 years, respectively. The relatively high protection level of 500 years is mainly attributed to the enormous monetary losses (revenues) in case of delayed completion of the project.Concrete face rockfill dam(CFRD)The primary reasons for selecting a CFRD for the Bakun project are availability of good quality rockfill, adequacy of foundation conditions after treatment and the tropical weather conditions (high rainfall) prevailing in Sarawak, which would have restricted the construction of an earthcore rockfill dam. In the last decade, significant developments were made in the design and construction of CFRD, as noted in numerous recent international conferences and publications. At present, the highest CFRD is the 187m high Aguamilpa dam in Mexico. Upon completion, the Bakun dam will be one of the worlds highest CFEDs. The designed Bakun dam (Fig.1) features a maximum height of 205m and a total volume of 15.6106 m3 with both upstream and downstream slopes of 1V:1.4H.The dam is provided with a reinforced concrete plinth, which will be founded on sound bedrock. Depending upon the water pressure and quality of bedrock, the width of the plinth will be about 5m to 10m. the concrete face area of the Bakun dam is approximately 120000m2, quite favorable, compared with other major CFRDs in the world. The thickness of the concrete slab is gradually increased from 30cm at the crest to a maximum of 93cm at the upstream dam toe. The concrete slab will be placed in 15m widths. The steel reinforcement will be approximately 0.3% of the slab cross section in each direction and be placed in single layer. It is planned to construct the concrete face slab in two or three stages, in accordance with the requirements of the river diversion scheme and the construction schedule.The main rockfill of dam is composed of the upstream zone 3A and the downstream zone 3B, as well as the intermediate 3C and 3D zones. When the reservoir is full, the hydrostatic load is primarily transferred to the zone 3A, causing additional compression in this zone. Thus the zone 3A should be made of particularly good quality greywacke and be well compacted to avoid excessive settlements.The downstream rockfill 3Bis also well graded rockfill from slightly weathered greywacke or better, similar to 3A, but will be placed in greater lifts of 1.5m so as to accommodate the oversize rock available from the required excavations and to allow a flexible blasting pattern and operation.The central zones, 3C and 3D, are considered as random rockfill zones, proportioned according to the geological conditions expected to be found at the site. This concept will provide flexibility to directly produce and place mixed rockfill material without stockpiling and to reduce the amount of waste material, reducing construction time and cost. In order to minimize seepage through the foundation and consequently eliminate the risk of piping and erosion, a continuous grout curtain will be provided along the plinth of the dam, consisting of three rows with a maximum depth of about 150m.SpillwayThe spillway is designed for a maximum discharge capacity of almost 15000m3/s, corresponding to the routed PMF with a peak inflow of 519000m3/s. for flood routing calculations, it was assumed that the PMF would enter the reservoir at maximum operation water level (el.228m as1) causing a maximum surcharge of 4.8m in the reservoir.The spillway comprises a gated overflow weir with four 15m wide, 24.5m high bays equipped with radial gates (15m21.25m) and stoplogs. Downstream of the weir, the chute contracts from its initial width of 72m to a width of 50.0m, resulting in a specific discharge of some 300 m3/s/m for the routed PMF peak outflow. An accidental opening of all four spillway gates at maximum reservoir operation water level of 228m as1 would result i