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In this study, to examine the effects of the fabric anisotropy of sand specimen and the anisotropic consolidation stress on the small strain stiffness, the bender elements test and the cyclic and monotonic triaxial tests were performed on several kinds of reconstituted and undisturbed sand samples. These laboratory test results were compared to the results of in-situ seismic surveys. Test results showed that the shear wave velocity estimated from the Young's modulus on triaxial test is lower than those from bender elements and in-situ tests. In particular, it was remarkably recognized in the sample including coarse materials. Therefore, in the case of a comparison of initial stiffness between the laboratory and in-situ tests, the shear wave velocity should be measured in the laboratory test in the same way as the in-situ test.

In this study, to examine the effect of the fabric anisotropy on elastic moduli (shear and Young's moduli), the bender element, cyclic and monotonic triaxial tests were performed on reconstituted clay specimens with different fabric characteristics. The specimens with the angle between the axial direction of the triaxial specimen and the bedding direction of 0 and 90 degrees were cut from the pre-consolidated clay block. These specimens were isotropically consolidated under several kinds of confining pressures. The shear wave velocities in three different directions (VH, HH, HV-wave) were measured by bender element tests, and the stiffness under wide ranges of strain levels up to failure were measured by cyclic and monotonic triaxial tests. Test results showed that; 1) the shear modulus obtained from the shear wave for propagating and vibrating horizontal to the bedding plane is higher than the others two kinds of moduli, 2) the horizontal Young's modulus at small strain is also higher than the vertical one, 3) the anisotropy of the elastic modulus of clay is larger than that with sand, but becomes lower with the increase in strain level and consolidation stress.

At present, almost all mountain tunnels in Japan are excavated and constructed utilizing the New Austrian Tunneling Method (NATM), which was advocated by Prof. Rabcewicz of Austria in 1964. In Japan, this method has been applied to tunnel construction since around 1978, after which there has been a subsequent decrease in the number of casualties during tunnel construction. However, there is still a relatively high incidence of labour accidents during tunnel construction when compared to incidence rates in the construction industry in general. During tunnel construction, rock fall events at the cutting face are a particularly characteristic of the type of accident that occurs. In this study, we analysed labour accidents that possess the characteristics of a rock fall event at a work site. We also introduced accident prevention measures against rock fall events.