Abstract
In previous major earthquakes, the damage and collapse of structures located in liquefied field which caused by site failure a common occurrence, and the problem of assessment of liquefaction possibility and discussion on the seismic response and stability of liquefied site is still issue of common concern in geotechnical earthquake engineering. To study the influence of the existence of structure on the seismic responses and stability of liquefiable sites, two groups of shaking table tests on liquefiable non-free field (with structure) and a free field (without structure) are performed. It can be summarized from the experimental results as following. The natural frequency of non-free field is larger and the damping ratio is smaller than that of a free field. For the weak seismic loading condition, the dynamic response of sites shows similar rules and trend. For the strong ground motion condition, soils in both experiments all liquefied obviously and the depth of liquefaction soil in the free field is significantly greater than that in the non-free field, besides, porewater pressure in the non-free field accumulated relately slow and the dissipated quickly from analysis of porewater pressure ratios in both experiments. The amplitudes of lateral displacements and acceleration of soil in the non-free field are obviously smaller than that in the free field caused by the effect of presence of the structure. In a word, the presence of structures will lead to the increase of site stiffness, site more difficult to liquefy, and the seismic stability of the non-free site is higher than that of the free site due to soil–structure interaction.
Highlights
As early as 1964, during the Alaska earthquake in USA and the Niigata Earthquake in Japan, the foundation bearing capacity reduction, uneven settlement and lateral spreading caused by soil liquefaction lead to the overturning and collapse of structures observed in the post-earthquake investigation
Study on soil liquefaction under seismic loadings is still an important research topic in geotechnical earthquake engineering [1], and many scholars have carried out a large number of studies on the liquefaction possibility discrimination of saturated sandy soil, liquefied soil-structure dynamic interaction and foundation failure of liquefied site by means of numerical calculation model [2,3,4,5], various experimental techniques [6,7,8,9,10,11] and theoretical method an analysis [12,13,14,15,16], and the seismic responses of various structures in liquefaction site were discussed in detail
It is no doubt that this series of shaking table experiments is qualitative one and proceeding precise quantitative analysis based on the data from shaking table tests to reflect the rules of any prototype site is difficult, and quantitative and further analysis on more problems such as the influence range of the pile-group on the development of porewater pressure in liquefied soil calls for refined numerical model to research
Summary
As early as 1964, during the Alaska earthquake in USA and the Niigata Earthquake in Japan, the foundation bearing capacity reduction, uneven settlement and lateral spreading caused by soil liquefaction lead to the overturning and collapse of structures observed in the post-earthquake investigation. Study on soil liquefaction under seismic loadings is still an important research topic in geotechnical earthquake engineering [1], and many scholars have carried out a large number of studies on the liquefaction possibility discrimination of saturated sandy soil, liquefied soil-structure dynamic interaction and foundation failure of liquefied site by means of numerical calculation model [2,3,4,5], various experimental techniques [6,7,8,9,10,11] and theoretical method an analysis [12,13,14,15,16], and the seismic responses of various structures in liquefaction site were discussed in detail. By comparing the experimental results from the free field and non-free field experiments, such as the dynamic characteristics, acceleration response, the rules of porewater pressure ratios in saturated sand layer, soil lateral displacements, etc., the influence of the existence of the structure on the dynamic characteristics and seismic stability of the liquefiable site is analyzed and summarized
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