Stabilitetsberäkningar och åtgärdsförslag vid islast på Skålandammen
Hydropower is an important source of energy in Sweden and accounts for about 46 % ofthe total energy production. Sweden has about 1 200 hydropower plants and with theintention of raising the pressure head of the water and to store water, dams are built by thepower plants. The storage reservoirs make it possible to adjust the energy production bydemand and season. Dams in connection to the reservoirs are subjected to additionalloading during periods of high floods or when an icecap in the winter is formed on thereservoirs. In order to maintain the dam safety, the power companies in Sweden areworking with guidelines for dam safety from RIDAS. An important part of the work of damsafety is FDU that is carried out with purposes of improving the work of dam safety. AFDU made for the Skålan dam in the River of Ljungan showed that the levels of the safetyfactors for sliding and overturning of the dam was not fulfilled when subjected to loadsfrom an icecap. The object of this thesis was to follow up the FDU and by carrying outextensive stability calculations on all parts of the Skålan dam, investigate what safetyfactors the different parts will get and also investigate some proposal measures in order toincrease the dam stability.The stability calculations for the dam have been performed according to directions inRIDAS at four loading cases. Loading case I and II means a water level to the retainedwater level and an ice load of 200 and 100 kN/m respectively. Loading case III and IVmeans a situation without ice load but with a water level to the retained water levelrespectively a water level to a meter above the retained water level. The stability of the damwas studied with regards to sliding and overturning. The results from the stabilitycalculations showed for both loading case I and II that the majority of the parts of theSkålan dam did not fulfill the levels of the safety factors. The calculations also showed thatsome parts of the dam did not fulfill the stability criteria of sliding at loading case III,which implies that these parts of the dam actually have not enough weight.The measure proposals studied were the ice preventive measures IR-elements andcirculation of the deep warm water and the stability increasing measure with pre strainedrock anchorages. The net present value (NVP) for the different measures were calculatedwith a life length of the dam estimated to 60 years. The results from the calculations of theNVP showed that the most economically feasible measure is circulation of the water butwhen considering the results from the stability calculations, the most suitable measure is therock anchorages. Therefore, a combination of rock anchorages on parts which not fulfillsthe stability criteria in combination with circulation of the water is suggested to be the bestmeasure.
Source Type:Master's Thesis
Keywords:dam safety the skålan ice load stability calculations preventive measures increasing
Date of Publication:09/02/2008