Analysis On Influence Of Special Soil Layer Construction On Site Earthquake Response

Since last century, we have realized that the site conditions have great influence to the ground-shaking and the seismic hazard. Consequently, as one of the site conditions, the soil formation also attracts the interests of us because its influence to seismic response. In the field of anti-seism engineering research, we study the influence of the soil formation to in situ seismic response from many aspects because of the soil formation's complication. This paper focuses tow special soil formations- silt (sullage) and hard-interlayer, which are often encountered in ocean engineering, and features the influence of in situ seismic response analysis brought by the two kinds of soils and ground-shaking input.This paper briefly sums up the present research of ground-shaking influence affected by the site conditions, mainly the soil formation, home and abroad, and the dominating estimate methods of soil ground-shaking at present. Thoroughly the paper introduces the one-dimension equivalent linearization method of soil seismic response, which is popular nowadays in china, and its advantages and disadvantages. Based on that, the paper calculates the in-situ seismic response under the different engineering conditions and ground-shaking of the tow kinds of special ocean soil formations through the one-dimension equivalent linearization method, analyzes the characteristics of seismic response in these situations,and confirms these characteristics through transfer function. The main content of the paper is as following:The influence on seismic response in silt:1.To the characteristic period (T_g) of earth surface acceleration spectrum, T_g of the soil with silt is 1-2.9 times of normal one. The depth and wave speed of silt affect T_g more than the ground-shaking input does. In this paper, T_g decreases 0.5s in average with the wave speed increases from 30m/s to 50m/s; and it increases 0.35s in average with the depth increased from 5m to 10m.2. To the ground peak acceleration (A_max), it is less than PGA in this paper; the larger the wave speed of silt, the thinner of thickness and large earthquake would enlarge it. In this paper, A_max increases 0.025g in average with the wave speed increases from 30m/s to 50m/s; and it decreases 0.018g in average with the depth increased from 5m to 10m.The influence on seismic response in hard interlayer:1.To the characteristic period (T_g) of earth surface acceleration spectrum, T_g of the soil with hard interlayer is 1.2-2.3 times of normal one. The ground-shaking input affect T_g more than the depth and thickness of hard interlayer does. T_g has no obvious change with different thickness; and it decreases 0.15s in average with the depth increases from 5m to14m.2. To the ground peak acceleration (A_max), it is less than PGA in this paper. The ground-shaking input affect A_max more than the depth and thickness of hard interlayer does. The influence of depth or thickness is too small to notice.Some advices of aseismatic are applied based on above-mentioned analysis results:1. When encounter silt in oceanographic engineering, large thickness and low wave speed of silt are disadvantageous to structure. Contrarily, when the wave speed of silt achieve a significant extent and it is thin, its'disadvantage will be lighter. In this case, we can take measures to reduce the effect. There are other measures to it, such as fill soil or drive pile in stable soil layer and etc.2. When encounter hard interlayer in oceanographic engineering, first, the ground-shaking input affect more on ground motion parameters than the depth and thickness of hard interlayer does. In the second place, as the influence of thickness is minor, the more we should consider is the depth of hard interlayer. The deeper the depth of hard interlayer, the better to structure. Contrarily, the shallower the depth of it, the greater the disadvantages to structure.Finally, some expectations are given aimed at the shortcomings of the paper that lead to further studies in the future.