Furuki Tatsuya 

Strength properties of crushed shell considering the use for geotechnical engineering

Toyota Hirofumi

In recent years, various efforts are actively engaged to achieve a recycling society with both environmental conservation and economic development. In fisheries industry, those efforts are accelerating. The main problem in this industry is disposal of shells such as scallops and oysters. Especially, scallops are main catch in Hokkaido and Aomori, and the shells without edible parts are estimated to reach about 280,000 tons.
　In Japan, appropriate disposal methods and effective using ways for this problem have not been established. As a result, scallop shells are piled up around fishing ports in Hokkaido. Along with this situation, environmental problems such as unpleasant odors and landscape deterioration have been newly triggered. To solve this problem, scallop shells have been used for construction materials such as packing material in caisson and backfill material of quay in fishing port because the scallop shells have enough strength for recycling. However, further use of the scallop shells is needed to reduce effectively the piled shells.
　A final goal of this study is to propose a geotechnical using method, in which the disposal shells are used to advantage with a large amount. Therefore, the direct shear test was conducted to grasp the peculiar shear properties, which might become problems to make artificial ground. The effects of the particle size distribution, bulk density and depositional angle of shells on shear properties are examined and compared to those in Toyoura sand.
　The following conclusions were obtained:
・The crushed shell has a greater mechanical anisotropy comparing with Toyoura sand.
・The shear strength s (= τmax) of the crashed shell is the greatest in the depositional angle of -45 ° regardless of its density.
・Although the crushed shell has a strong anisotropy, it can be used as a ground material because its shear strength exceeds Toyoura sand. 
・The shear strength of the crushed shell is almost identical despite of its density. Therefore, it can become an easily usable ground material because it does not require heavy compaction for making artificial ground.