Leaching Characteristic Of Fly Ash With Desulfurization Gypsum And Seepage Stability Analysis Of Ash Dam

Fly ash and desulfurization gypsum are solid wastes of thermal power plant,with large production.Because of its low utilization rate,the desulfurization gypsum needs to be stored largely.At present,the fly ash has been widely used in ash dam heightening.On the other hand,due to the limited space,the desulfurization gypsum is often mixed with fly ash,so it is necessary to study the possibility to use the mixture as ash dam foundation.To deal with the problem of desulfurization gypsum mixing in the ash bank,a series of chemical,physical and mechanical tests are carried out to research engineering properties of Fly ash with desulfurization gypsum.And GeoStudio Software is used to calculate the seepage and stability of ash dam and its foundation.The main contents of this thesis are as follows:?1?The fly ash and desulfurized gypsum,which from the Gongxian power plant in Sichuan,were tested and studied,and the mineral composition,specific gravity,particle size distribution and the limit water content were measured.It is found that the main mineral components of fly ash are quartz and mullite,and it is silty sand;the main components of desulfurization gypsum is calcium sulfate dehydrate,and the gypsum is low liquid limit silt.?2?Experimental study on the fly ash with different content of desulfurization gypsum?10%,30%and 50%?was conducted to determine the specific gravity,compaction,compressibility,permeability,shear strength,and leaching properties of the mixtures.The results show that both the fly ash and the mixture are medium and low compressibility materials with weak permeability,and the strength of the three kinds of mixture is higher than fly ash,and the compression and internal friction angle of the test material are influenced by the fine grain content,which are negatively related to the content of the desulphurized gypsum.?3?Leaching test on the fly ash with different content of desulfurization gypsum was conducted for the following two purposes:Analysing the types and content of soluble substances in the mixture;Analysing the influence of eluviation on the physical and mechanical properties of the mixture.The results show that the peak and stable value of SO₄^2-ion concentration in the filtrate increase with the increase of gypsum content in the mixture;the permeability coefficient increases slightly with time during the leaching process;the cohesive force of the sample after leaching is reduced and the angle of internal friction is slightly increased;after leaching,with the increase of gypsum content,the permeability coefficient and strength of the mixture decrease.?4?Analysis of seepage and dam foundation stability of ash dam are conducted.The results show that the distribution regularity of the phreatic line of different material is similar,and the phreatic line did not exceed the dam slope under various conditions.The safety coefficient of the dam based on different materials is greater than the minimum of the standard,and the dam foundation is stable.Among them,the safety coefficient of the gypsum mixture with gypsum 30%is the highest when it is used as the dam foundation material.