The Effects of Near and Far-Field Earthquakes on Soil-Foundation-Structure in Vicinity of Excavation

The influence of site effects on seismic events is indeed significant and plays a pivotal role in earthquake occurrences. Site effects can either amplify or dampen earthquake waves, making the study of site effects essential in seismic geotechnics. Recent earthquake records indicate that earthquakes in the near area exhibit different characteristics compared to those in the far area. The movement characteristics in the near area are closely related to the seismic source mechanism, the direction of fault rupture concerning the structure, and the direction of fault slip. Near-field movements often exhibit distinct features such as the generation of pulses due to directivity and permanent displacement effects. These movement pulses typically include one or more separate pulses in the time history of acceleration, velocity, and displacement, particularly in the time history of speed. Previous research has demonstrated that deep excavations near structures can increase lateral displacement. The extent of this increase or decrease depends on various factors, including excavation depth, earthquake type, and the foundation of adjacent structures. This study aims to investigate the effects of near-field and far-field earthquakes in the presence of an equivalent load representing high-rise buildings. The study utilizes an efficient and accurate model of a soil-foundation-structure system. The findings reveal that, in the comparison of the Kobe earthquake in the far and near fields, the far-field earthquake has had a greater effect on the excavation. The far-field earthquake experiences a significant increase in maximum acceleration recorded at the point under the foundation compared to the corresponding models in the near-field. Additionally, the permanent horizontal movement of the excavation's edge, the permanent settlement, and the uplift of the foundation have increased in the presence of the excavation rather than without excavation models.

Keywords:

Site Effect , Near-field , Far-field , Deep Excavation , Soil-Foundation-Structure