Use of Flyash in the Construction of Low Height Dams: an Experimental Study

In the alluvial stage of a river, very often the civil engineers have to construct works like dikes, guide bunds, detention dams, earthen dams and debris dams etc. Generally, in order to keep the cost of construction low, the locally available soil is used in the construction of these structures, which results in the loss of topsoil and otherwise cultivable land. In the present study, an effort has been made to utilize flyash on mass scale for such constructions, specially when they are in the near vicinity of thermal power plants or where the transportation cost is within reasonable limit. In India at present flyash production is about 106 Mt per year and about one acre of land is required for the disposal of flyash generated from 1 MW of power generation for its design period. Flyash from Dadri thermal power station was collected and tested for its seepage resistivity, at 15% cement the flyash-cement mixture gives a permeability value of 1.29 e-5 cm/s, which is in the initial range of clay. The variation in permeability with percentage of cement was tested using flyash from other sources, namely, Badarpur thermal power station, New Delhi and Harduaganj thermal power station, UP 1 . It has been found that at 15% cement the value of permeability in all the three cases was almost the same 1 . A model study of a dam with core material (flyash + 15% cement) and shell material (flyash + 5% cement) was also carried out. The experimental results suggested that a flyash + 15% cement could be useful as a good core material with negligible/insignificant seepage.