The effect of soil improvement under earthquake loading conditions

Abstract

Earthquake is the rapid and sudden release of a huge energy resulting from the rupture of earth crust which cause the creation of seismic waves. The effect of earthquakes on soil conditions has been investigating for a long time by earthquake engineers. The common practice in the past was mainly pseudo-static analysis and experiences. In the last ten years due to development of finite element programs to overcome many complex problems, researchers started to use computer programs to simulate and analyze earthquake conditions. In that study, effect of soil improvement on site response during earthquake loading conditions is studied through response spectrum, PGA values measured from different points and amplification factors. For that purpose, three models are created with same dimensions and material properties, which represents the initial condition, raft foundation condition and deep foundation condition. Seven-time history records are selected and scaled with appropriate selection, scaling and filtering criteria. Results show that, the soil improvement through pile construction does not create any shifts in the response spectrum, thus it does not change the soil class in most of the cases for the given loading and soil conditions, but for some records, the spectrum may change depending on the loading. Beside we checked the PGA values at different points. It is seen that there is amplification as the wave travels within soil in most cases. And based on amplification factors, it is stated that amplification factors of deep foundation are lower than initial condition. Thus, the soil improvement through the construction of piles deamplifies the earthquake loading much better than natural condition.