海底堆積物からみた錨効きについて : 伊勢湾(央部および奥部)

概要

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The bottom material is covered with muddy soil with Mdφ=6.2 to 8.7, which is good in sifting power, as is often seen in an inland bay. The ignition loss of the bottom material is 7.0 to 13.0 while the surface course consists of black mud. The natural water content in per cent of dry weight is over 100% even at about 1m deep. The liquidity index was 1.15 to 1.43, showing an instability or a tendency to be liquified easily. Although plotted I_p-W_L values in a plasticity chart fall around the A-line, we have W_L=70 to 150%, W_p=30 to 60%, and I_p=50 to 100%, which are greater than ordinary values. Both void ratio and unit weight was in correspondence with the water content in per cent of dry weight, while the shearing stress as measured by a hand vane tester was 0.061kg/cm^2 at 1.0m deep. The anchor towing force as measured in muddy soil was about three times the anchor weight. From this, it is estimated that the holding power of an anchor in the bay is around these values because the surface course in the bay contains only about 5% of sandy soil. Since these values correspond to the case when the anchor assumes a normal posture, it should be noted that the holding power decreases when the anchor starts dragging.
社団法人日本航海学会の論文
1987-03-25