Investigation of the Effects of Water Content and Relative Density on Soil Dominant Frequency in Separate Grained Soils by Microtremor Method

Abstract

Determination of earthquake-soil-structure relationships is very important especially in reducing the damages that may occur in earthquakes. Building damages in earthquakes change depending on the relationship between the soil structure on which they lied and the soil transfer function. Changes occur in the amplitude of the seismic waves depending on some physical properties of the soil environment in which they spread. This paper presents the effects of water content and relative density on soil dominant frequency using the experimental application for the first time. In this study, metal cylindrical molds with a diameter of 30 cm and a height of 50 cm were prepared. These molds were filled with sand in different relative densities (60% and 80%). Samples were prepared by adding waste rubber particles at different rates (0%, 0.5%, 1%, 2% by weight) to this sand. The soil dominant frequency and amplification factor were determined with the microtremor method by measuring 60 minutes of measurement on each cylinder for different water contents (0%, 5%, 10%, 15%) using a broadband seismometer. Microtremor results were analyzed by using the Horizontal/Vertical spectral ratio method. The data in the time environment were moved to the frequency environment with the Fourier transform and analyzes of the frequency contents and amplitudes of the data were conducted. As a result of the experiments, it has been observed that the waste rubber particles added to the sand affect the soil amplification factor in a decreasing way. Besides, it was concluded that the most suitable environment in terms of earthquake-soil relationship will be obtained with 60% relative density, 1% waste tire and 0% water content. Likewise, it is also concluded that the most suitable environment will be achieved in 0% water content environments with 80%  relative density and 0.5% waste tire ratio. It has been observed that the composite material prepared with this waste tire has positive effects on the earthquake-soil-structure relationship.