Influence of particle size on the shear strength of mineral filter cakes

In this study, the effect of particle size of minerals, calcite and quartz, on the shear strength of filter cakes is investigated in the presence and absence of the nonionic surfactant. The shear strength of the filter cakes is measured by using BOS, shear strength measurement device, which is designed in our laboratory. The shear strength measurements of mineral filter cakes are depended on the applied pressure during the filtration and compression, saturation degree of filter cakes, particle shape as well as particle size and surface tension. The applied pressure was taken as constant during the filtration and compression steps. Measurements were repeated in two different saturation degree regions, S= 70- 80% and 0- 10%. The laboratory experiments showed that the shear strength of filter cakes is decreasing with the increasing of the mineral particle size. The addition of nonionic surfactant to the slurry is increased the shear strength values, but it is not changed the influence of particle size on the shear strength. The following relations can be written between the shear strength and mineral particle size; in the bridging region, S= 0-10% in the capillary region, S= 70-80%.