Modification of multi -direction dynamic loading apparatus to simulate earthquake in soil specimens

Determination of dynamic properties of soils in laboratory such as damping ratio and shear modulus is possible by simulation of earthquake waves. The results of cyclic tri-axial strength test were used for evaluating the ability of a soil to resist the shear stresses induced in a soil mass due to earthquake or other cyclic loading. For this purpose, the cyclic tri-axial apparatus was made in Shahid Chamran University to simulate P and S waves of earthquake in unsaturated soil. Because these waves in saturated soil conditions can cause different effects, such as liquefaction in loose sandy soils. The purpose of this paper is to introduce the changes that were made to the original device in order to simulate liquefaction in the soil specimens due to cyclic loading. The features that were modified were transducers with better sensitivity and some features required to control loading rate for making equalization of pore pressure within the soil specimen. For evaluating the accuracy of the apparatus, sandy soil specimens mixed with 10% and 20% of crushed rubber were subjected to cyclic tri-axial loading. Results of the experiment were reasonable and close to reality.

Keywords:

cyclic tri-axial test , saturate soil , liquefaction , damping ratio , dynamic properties , loading rate