Research on The Establishment of An Earthquake Response Analysis Scheme and The Improvement in Damping Performance of A New Type of Seismic Isolation System Composed of Piles Covered by Pipes and Partial Soil Improvement with Damping Devices

第一年，在试验场地上采用常规技术建造了一个面积为2.4m × 2.4m、高度为1.0m的基础块（CF），并通过四根水泥土柱（直径：600mm，长度：2.5m）进行了强迫振动试验。第二年，在CF以东6 m处采用与前一年相同的技术建造了一个相同尺寸的新基础块，并通过改变侧面条件进行了强迫振动试验。在本试验的最后阶段（基础侧面的沟槽深度为0.8m），将阻尼复合材料回填到新基础块（IF）的沟槽中，并进行强迫振动试验。阻尼材料是沥青与碎石和废轮胎尖的混合物。实验结束后，继续进行地震观测。通过试验、地震观测和仿真分析，得出了如下主要新结论：IF比CF能更好地定量地阐明阻尼减振性能。首先，从强迫振动试验的结果可以确认，与CF的情况相比，在IF的情况下，在主频率处每单位激振力的响应位移减小了约30%。其次，根据包含2004年新新泻县中地震在内的32个波的地震观测数据推测的传递函数，确认了IF比CF的响应降低更多。但其衰减率不及强迫振动试验的衰减率。这是由于小尺寸的基础块和小输入从侧面。

In the initial year, a foundation block (CF) with a square area of 2.4m x 2.4m and with a height of 1.0m was structured by a conventional technique on the experiment site improved by four soil cement columns (diameter:600mm, length:2.5m), and forced vibration tests were conducted. In the next year, a new foundation block of the same size was constructed 6m to the east of CF by the same technique as the previous year, and forced vibration tests were conducted by changing the conditions of the side surface. At the last stage of this test (the trench depth of the side surface of foundation was 0.8m), a damping composite material was backfilled into the trench of the new foundation block (IF), and forced vibration tests were performed. The damping material is a mixture of asphalt with crushed stones and scrap tire tips. After the experiment, the earthquake observation has been continued. The main new findings obtained from the tests, the earthquake observation and the simulation analyses of them are as follows:The IF could quantitatively clarify damping performance and vibration reduction better than the CF. First of all, from the result of the forced vibration tests, it was confirmed that in the case of IF, the response displacement per unit of excitation force was reduced approximately 30% at the dominant frequency, being compared to the case of CF. Next, more response reduction was confirmed in the IF than the CF from the transfer functions, which were presumed from the data of earthquake observations of 32 waves including the Mid Niigata Prefecture Earthquake in 2004. However, its decrease ratio was not to the extent of the case of forced vibration tests. It is attributed to the small sizes of foundation blocks and the small inputs from the side surfaces.