Behavior of manufactured sand under cyclic loading

The disposal or utilization of industrial wastes or by products in powder size is an important issue for all over the world. The fly ash, as one of the most significant waste of this industry, with millions of tons of production every year, poses problems such as handling, disposal and stability of the disposal sites due to its silt size etc. Manufacturing geomaterials using powder waste material has great potential for safe disposal and utilization when needed. To solve the growing disposal problems, fly ash has been pelletized to manufacture sand in two different gradations and its cyclic behavior has been evaluated in this thesis. In order to evaluate the performance of fly ash pellets; natural sand samples and fly ash pellets with similar size samples were prepared. The fly ash pellets have high porosity and low unit weight similar to those of calcareous sands. Due to lack of information of fly ash pellets, the literature related to the cyclic behavior of calcareous sand is investigated. A series of isotropically consolidated undrained monotonic triaxial tests are performed and internal friction angles are determined. Two quarzatic sands, poorly graded Kilyos Sand and well graded Şile Sand were used as control for comparison to manufactured fly ash pellets with similar gradations. For both natural and manufactured sand, samples were prepared for three different relative densities, loose to dense. The range of internal friction angles of sands studied was between 36-40°. For the manufactured sand the range was between 31- 38°. The natural and manufactured sands were subjected to constant volume cyclic direct simple shear tests under 50 and 100kPa consolidation pressures. The cyclic stress ratios of 0.2 and 0.3 and cycle period of 1 and 2 were applied. The secant shear moduli and the damping ratio are calculated. These values are found to be similar to quartz sands.