Evaluation for Soil Liquefaction Due to Long Duration Earthquakes with Low Acceleration
Past studies show that soil liquefaction due to a long duration earthquake with low acceleration, for example as observed in the Tokyo Bay area in the 2011 Great East Japan Earthquake, is largely affected by liquefaction strength for a large number of loading cycles. It is, therefore, extremely important to know the liquefaction resistance for a large number of loading cycles. This paper describes the results of the hollow cylindrical cyclic torsion shear tests that were conducted to ascertain the effects of grain size distributions on liquefaction resistance for a large number of loading cycles. The test results clearly show that the tendency of a decrease in liquefaction resistance for a large number of loading cycles is influenced by mean grain size, inclination of grain size distribution, and so on. Finally, the effect of liquefaction resistance curve characteristics on the assessment of liquefaction potential is examined using the cumulative damage theory.
Equivalent Uniform Cycle Concept for Soil Dynamics
While additional studies of this nature would be appropriate, especially using direction independent tests such as cyclic simple shear, torsion shear, or shaking table, the writers feel justified in concluding that the data presented herein generally confirm the validity of the equivalent cycle or the cumulative damage method of dealing with irregular loading effects on soil. Some other aspects include a clarification of the relations between damage potential and equivalent number of uniform cycles, certain peculiarities of the cyclic triaxial test on saturated sands that may not be significant for clays, and a perspective comparison of the range of data scatter for cyclic tests on soil as compared with other materials. Thus, while the damage potential or equivalent cyclic concept may not be exactly valid for all cases, its continued use in the field of seismic stability analyses of soils seems to be a valid pragmatic approach.
Representation of systems disturbed by wide band noise
In this paper, a method of handling and working with wide band noise is developed. We represent wide band noise as a distributed delay of white noise and use it to reduce a nonlinear system disturbed by wide band noise to a nonlinear system disturbed by white noise. An application of this reduction to a nonlinear filtering problem under a wide band noise disturbance is discussed.