Earthquake resistant reliable design on agricultural hydraulic structures.

首先，在由硅藻泥岩组成的坝址处，利用井下和折射波传播技术进行纵波和横波速度的测量，以估计原位速度的分布。用井下法和折射法测得的压缩波速度随深度的增加而线性增加，而剪切波速度则与深度的1/6-1/7次方成正比，这与路堤实测速度的分布不同。其次，还进行了同一场地的微动观测，以预测本征频率。观测到的主要频率为0.3Hz，因此，利用上述剪切波速度分布估计表层存款深度约为400 m。第三，为了研究小应变区的变形特征，对具有力学各向异性的硅藻泥岩进行了垂直和水平方向的圆柱形试件的三轴压缩和动力试验。结果表明：（1）应变水平越高的试件，其横纵弹性模量之比越大。(2)动力试验结果表明，即使在10 ~（？）应变水平下，竖向杨氏模量也存在一定的应变依赖<-6>性.最后，利用地震资料，根据极值理论，得到了该场地年最大加速度分布的上限值，并进行了地震危险性分析.结果表明，100年的预期加速度值为160 gal，这与目前的设计地面加速度值大致相同，而上限加速度值约为450 gal，这在抗震设计中必须考虑。

Firstly, measurements of compressive and shear wave velocities are carried out by downhole and refraction wave propagation techniques at dam site composed of Diatomaceous mudstone to estimate the distributions of in situ velocities. The compressive wave velocities obtained from both downhole and refraction methods increase linearly with depth, whereas the shear wave velocities increase in proportion to a function of the power of 1/6-1/7 of depth, which is different from the distribution of velocities measured at an embankment.Secondly, observations of micro tremor are also conducted to anticipate the eigen frequency at same site. The predominant frequency observed is 0.3Hz, so that the depth of suface deposit is estimated about 400m using above-mentioned distributions of shear wave velocities.Thirdly, to investigate the deformation characteristics in small strain region, both triaxial compression (UU) and dynamic tests are performed in cylindrical specimens of Diatomaceous mudstone prepared in vertical and horizontal directions with mechanical anisotropy. The results obtained are as follows :(1) Specimens with the higher strain level exhibit the greater anisotropy as reflected by the ratio between the horizontal to vertical Young's moduli.(2) The dynamic test results indicate that the strain dependency of Young's modulus in vertical direction exists to some degree even at 10^<-6> strain level.Finally, the seismic risk analysis is performed employing the distribution of annual maximum acceleration with an upper bound limit at above-mentioned site, obtained from a theory of extremes using seismological data. As a result, it is shown that the acceleration value expected during 100 years is 160gal, which is about the same as the present design ground acceleration, whereas the upper limit acceleration value is about 450gal ; this must be taken into account in the eartquake resistant design.