LABORATORY STUDIES ON THE EFFECT OF LOADING SPEED ON MECHANICAL PROPERTIES OF COHESIVE SOILS

Dynamic loads are usually of two forms: vibration and shock. Shock loads are applied in a short time interval. Cyclic loads, such as earthquake, and the load at machinery foundations, have different speeds depending on their frequencies. The present research provides a laboratory study onthe effects of loading speeds on mechanical properties of clay and silty clay. Commercial kaolinite clay as well as Rasht silty clay was used in this study. Samples were compressed in optimum humidity and according to standard proctor test; then, unconfined compression test and direct shear test were performed at different loading speeds. The results suggest that increase in loading rate significantly increases the unconfined compression strength. The shear test leads to the same results showing that increase in loading speed results in higher shear strength. Comparison of angle of internal friction and cohesion at different loading speeds shows that higher loading speeds increases cohesion and angle of internal friction. This can be attributed to viscosity of cohesive soils. Changes in modulus of deformation were also studied at different loading speeds. The findings of this study can provide us with more accurate judgment on the bearing capacity and settlement of different types of cohesive soils at various loading speeds.

کلیدواژه ها:

Loading Speed ، Cohesive Soils ، Unconfined Compression Test ، Direct Shear Test