海底堆積物からみた錨効きについて-II : 伊勢湾および渥美湾

抄録

The authors investigated the submarine deposits in both Ise Bay and Atsumi Bay to find out the relation between the nature of the deposits and the holding power of an anchor. As a result, it was found that the holding power relates to the grain size of the deposits and that it increases as the deposit grain becomes coarser. When the grain size of the deposit was represented by three kinds of factors, i.e. mud content, Mdφ and Mφ, it was found that the correlation coefficients to the holding power (Eq.s (1), (3) and (4) in this report) were almost the same for each factor. Therefore any one of the above factors may be used as the criterion for the holding power of an anchor. It is considered, however, that it is unbiased to employ either Mdφ or Mφ, each of which fully takes into account the grain diameter, instead of the mud content. Fig.7 shows the holding power of an anchor expressed in terms of Mdφ in both bays. Collating these results with the sea chart, we can see that the points with bottom-material-notations of "S" or "S.G" give the good holding power. However, it should be noted here, that when the anchor flukes face upward the holding power decreases as the deposit grain becomes coarser, contrary to the above. (Refer to Fig.7.) In addition, when the holding power of an anchor is evaluated based on the grain size, the locality characteristics varying depending on the depositing circumstances should be examined for each bay, because it is considered that they also affect the holding power.