Numerisk modellering av deformationer och spänningar i betongplattan för höga Concrete Face Rockfill Dams
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Chinas economy is growing rapidly and this creates an enormous demand for energy. China’s government has over the years constructed many hydropower stations to meet some of this demand. A crucial part of a hydropower station is the reservoir, in order to create one a dam is needed. With the reservoir the hydropower station can store and produce electricity on demand.The concrete face rockfill dam (CFRD) is a dam type that consists of a concrete slab that lies on the upstream slope of an embankment. The Concrete face works as an impervious layer. The slab is supported by the rockfill embankment, which is constructed in different zones with different purposes and features. CFRD has been accepted in China because of the safety and also for economic reasons.The CFRD has been constructed at numerous places in China, the dam type is under continuous development at the China Institute of Water resources and Hydropower Research (IWHR). As the development of CFRD continues the height of these dams increases. There is one CFRD in China that is in the planning stage right now which will have a total height of 257 meters and in the future China plans to build dams with heights over 300 meter.There have been several high CFRDs that have had failure due to rupture in the face slab. Movement in the embankment causes larger stresses in the face slab. If these stresses increase enough it will lead to spalling failure in the face slab. The rupture will then significantly escalate the seepage through the dam body. These problems have come as a surprise as it were not foreseen by either numerical modeling or empiric design methods.IWHR conducts research on the problem with rupture in the slab of high CFRD, this master thesis is a small part of that work. In this study two numerical analyses with the finite element method (FEM) have been conducted. The first analysis tries to answer how stresses and deformations change with an increased height of the dam. The second analysis models the performance of the dam when stiffness is decreased in one of the rockfill zones in the dam.When the dam height is increased the deformations in the cross-valley direction magnifies, these will cause larger compression stresses in the center of the slab. Since the stresses in the cross-valley direction increase faster than the confining water pressure there is an enhanced risk of rupture in the face slab. When the stiffness modulus of the downstream rockfill zone, referred to as zone 3C, is decreased the result will be an increased deflection of the concrete slabs upper part. The stresses in the cross-valley direction do not enlarge with lower stiffness of zone 3C. Therefore the risk of rupture in the slab will not increase.
Place, publisher, year, edition, pages
2015. , 57 p.
Teknik, Rupture, CFRD, spalling failure, 3D-modeling, face slab, FEM
IdentifiersURN: urn:nbn:se:ltu:diva-53185Local ID: a3c11792-85de-4eb8-bc14-5bef13df26adOAI: oai:DiVA.org:ltu-53185DiVA: diva2:1026559
Subject / course
Student thesis, at least 30 credits
Civil Engineering, master's level
Validerat; 20151214 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved