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Liquefaction of Bulk Cargo and its Prevention

散货液化及其预防

基本信息

批准号：
01460164
负责人：
URA Tamaki
金额：
$ 3.58万
依托单位：
Insitute of Industrial Science, University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1991
项目状态：
已结题

项目摘要

Bulk cargoes should be prevented from shifting and liquefaction for the safety of transport by ships. Liquefaction occurs when the moisture content of the cargo is larger than a specific value which is called as the Flow Moisture Point (FMP). Though several methods have been proposed for its determination, no one is omnipotent for mineral concentrates, similar materials, and coals. In this program, the phenomenon of liquefaction is investigated theoretically and experimentally and a new method called the "Penetration Method (PM)" was proposed and submitted to the International Maritime Organization for inclusion in the BC Code. To judge the occurrence of liquefaction, measurement of residual shearing strength is the most convenient way for bulk cargoes. The procedure of the PM is as follows : (1)Put a sample, of which moisture content has been determined, in a cylindrial container ; (2) Set a penetration bit on the surface of the sample ; (3) Vibrate vertically the container with more … More than 3G acceleration ; (4) Measure the depth of penetration after 6 minutes ; (5) When the depth of penetration is less than a specific value, the moisture content of the sample is more than the FMP. This procedure was examined with several concentrates and coals, and it was concluded that the PM does not depend on the skill of the operator and repeatability of the result is sufficient. It should be emphasized that this method can be applicable to high cohesive materials.The liquefaction strength of coal was measured through the triaxial cyclic compression test in cases of saturated and non-saturated conditions. It is concluded that the stress ratio when the coal is saturated is 0.15 though it is twice larger when the coal is not saturated.In the cargo hold, frequency of external force, which corresponds to the cycle of rolling motion, is so slow that the excess pore pressure may dissipate to the surface and the liquefaction strength of cargo virtually increases. In other case, the pore air pressure may decrease the liquefaction strength depending of the permeability. In this program, permeability of mineral concentrates and coals are also investigated experimentally. Less

为了船舶运输的安全，应防止散装货物移动和液化。当货物的含水量大于一个特定的值时，液化发生，该特定的值被称为流动水分点（FMP）。尽管已经提出了多种方法来测定它，但没有一种方法对精矿、类似材料和煤炭是万能的。在这个项目中，液化现象进行了理论和实验研究，并提出了一种新的方法，称为“渗透法（PM）”，并提交给国际海事组织列入BC规则。对于散装货物而言，测定剩余抗剪强度是判断液化发生的最方便的方法。PM的步骤如下：（1）将测定了水分含量的样品置于圆柱形容器中;（2）在样品表面设置渗透钻头;（3）用更多的空气垂直振动容器。 ...更多信息 3G加速;（4）6分钟后测量渗透深度;（5）当渗透深度小于特定值时，样品的含水量大于FMP。用几种精矿和煤对该程序进行了检查，得出的结论是PM不依赖于操作员的技能，结果的可重复性是足够的。通过饱和和非饱和条件下煤的三轴循环压缩试验，测定了煤的液化强度。结果表明，煤饱和时的应力比为0.15，而煤未饱和时的应力比是饱和时的2倍，在货舱内，与摇摆运动周期相对应的外力频率很慢，从而使超静孔隙压力消散到表面，货物的液化强度实际上增加了。在其他情况下，孔隙空气压力可能会降低液化强度取决于渗透性。在这个程序中，矿物精矿和煤的渗透性也进行了实验研究。少