Development of new procedure
4 For the above reasons, Japan recognized the need to develop a procedure for evaluating the liquefaction potential of solid bulk materials. Then, the research was carried out and the procedure was developed. Results of the research were reported in DSC 2/12/1.
5 We also recognized that the problem of the scope of the application of the requirement is common to all Member States of IMO. Then, we made the procedure public at the second session of the Sub-Committee and proposed the utilization of the procedure as an MSC/Circular. We consider that the utilization of the procedure contributes to maritime safety.
6 It should be noted that the procedure is not for determining TMLs. The procedure is a complementary one for the implementation of the requirement for liquefaction materials. The procedure is used in the case that the shipper or the master has doubts that the cargo, which is not listed in appendix A of the BC Code, may liquefy at high moisture content.
Discussion on the procedure
7 The procedure was discussed at the last session of the Sub-Committee. Applying the liquefaction potential test (LPT), i.e. the new test procedure for determining the liquefaction potential of solid bulk materials presented in our paper (DSC 2/12/1), for "sedimentary galena", Poland recognized the effectiveness of the test procedure (DSC 3/11/2). Furthermore, they pointed out that the number of droppings of the hammer in the compaction procedure of the test should be amended. We fully agree with the comment made by Poland and amended the compaction procedure in the draft of the test procedure.
8 Canada pointed out some problems and editorial issues (DSC 3/11/5). According to the comments made by Canada, we amended the draft of the test procedure. The principle of the procedure is explained, again, in this paper. A revised version of the draft MSC/Circular is presented in the annex.
Principle of the procedure
9 The comprehensive procedure consists of two judgements. One is using the grain size distribution of the sample as an index and the other one, i.e. the LPT. is using the degree of saturation of the sample after the drainage as an index.
10 Regarding the relation between the characteristics of liquefaction and the grain size distribution, it is well known that the coarse materials are not liable to liquefy. To judge the liquefaction potential of the material by using the grain size distribution as an index, the representative value of the grain size accumulation curve should be selected. The liquefaction phenomenon is deeply related to the characteristics of drainage of water (moisture migration). Strictly speaking, characteristics of drainage of water are related to the other parameters, e.g., uniformity coefficient which have much effect on void ratio, as pointed out by Canada. However, it is not practical to discuss the characteristics of drainage in detail for the evaluation of the liquefaction potential of solid bulk cargoes. Therefore, it is rational to select the effective size D10, i.e. the primary parameter of the characteristics of drainage of water, as the representative value of the grain size accumulation curve. Taking into account the issue that the criterion of the judgement by using the effective size as an index has sufficient safety margin, it is not necessary, to introduce the uniformity coefficient to the judgement by using the grain size distribution as an index.
11 Regarding the LPT, the principle of the Proctor/Fagerberg test procedure described in D.1.3 of the BC Code was introduced in the test. The Proctor/Fagerberg test procedure is based on the principle that the material having a low degree of saturation is not liable to liquefy. The basic principle of the LPT is to rule out the possibility of liquefaction of a material by the judgement that the degree of saturation of the material is not liable to reach the criterion under the ordinary drained condition.
