This paper presents a new method of simulation for unsymmetrical faults in power system. The new method is based on the phase coordinate method. The symmetrical component method has been used traditionally for unbalanced faults in power system. This is mainly because the synchronous generators can be easily treated by the method. However, when analyzing a system that has elements with unsymmetrical impedance, the symmetrical component method can not be used. In such cases, the simulations can be easily executed by using the phase coordinate method. However, there are few papers that present detailed procedures of simulation based on the phase coordinate method. This paper, at first, presents phase coordinate models of the elements in power system; i.e., synchronous generator, transmission line, transformer and load. Next it presents a method of power flow calculation of a power system including elements with unsymmetrical impedances. Finally it presents detailed procedures of simulations based on the phase coordinate models derived.

In order to recycle dredged soil, our research group developed interlocking blocks from dredged soil. Dredged soil interlocking blocks (350 mm in width, 350 mm in depth and 100 mm-150 mm in height) were made from soft clay dredged at the Kanmon run. They were produced with the constant dehydration pressure 5 MPa and cement content of 15%, 20% and 25% per the dry weight of clay. The unconfined compression test and bending test were carried out to investigate material characteristics of dredged soil interlocking blocks in the water for six months. On the other hand, in order to check the effect of interlocking blocks, a road was constructed by using interlocking blocks on the surface and, as a roadbed material, dredged and dehydrated soil and crushed stone for mechanical stabilization were used. Characteristics of dispersion of traffic load and settlement were evaluated by running experiments. Stress was measured by four earth pressure gauges and settlement was measured by surveying. The following conclusions are obtained: (1) There was close relationship between unconfined compressive strength and water-cement ratio. Therefore, it is concluded that unconfined compressive strength of dredged soil blocks are controlled by water-cement ratio. (2) Dredged and dehydrated soil can disperse traffic load effectively. (3) Soil-concrete blocks can't disperse traffic load effectively, but have sinking suppressing effect when using dredged and dehydrated soil as roadbed material.

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