Enclosure (2): Preliminary draft of the report
Comments
3. Why only for granulated slags.
4. There are numerous methods to determine the Liquefaction Potential of materials.
5. The draft report should also mention that the Laboratory Test Results of the proposed Japanese proposal will be compared and validated by the following:
ASTM Designation D 5311
Standard Test Method for
Load Controlled Cyclic Triaxial Strength of Soil
Enclosure (2) : Coordinator's comments on the answer by Canada
Enclosure (1) : Summary of discussion items of circular No.1
1.1 b) & c) State of art and definition of liquefaction
We noted the various definitions of liquefaction in comments by Canada.
In the BC Code, the basic procedure for determining TML is the Flow Table Test Procedure, which applies the cyclic load to specimen. The other procedures for determining TML., i.e., Penetration Test Procedure and Proctor/Fagerberg Test Procedure, were evaluated by comparing the test results to the TMLs or FMPs obtained through the Flow Table Test. It can, therefore, be said that liquefaction of solid bulk cargoes is evaluated by the test which applies cyclic load to specimen, primarily. In view of this, we considered that it is appropriate to use the word "liquefaction" with the following simple definition in the discussion on carriage of solid bulk cargoes:
"Liquefaction is the phenomena that wet granular materials lose their shear strength resulted from increase of pore pressure due to cyclic loading."
Liquefaction defined by the following sentences proposed by Canada has wider meaning in view of forces applied to the material.
"Liquefaction (spontaneous liquefaction) - the sudden large decrease of the shearing resistance of a cohesionless soil. It is caused by a collapse of the structure by shock or other type of strain and is associated with a sudden but temporary increase of the prefluid pressure. It involves a temporary transformation of the material into a fluid mass."
Taking both definitions into consideration, it is obvious that increase of pore pressure is essential phenomenon of liquefaction.
We would like to reflect the discussion in the progress report to DSC 5.
2.3 Method of judgment of the application of the requirements
As Canada pointed out, it is well known that the load controlled cyclic triaxial strength test is the basic method for evaluating the characteristics of liquefaction of granular materials. For the development of Japanese Penetration Method, we conducted the cyclic triaxial tests for coals.
It should be noted that the methods for determining TML described in Appendix D of the BC Code, in which the safety margins are introduced, are already utilized and liquefaction of solid bulk cargoes has been prevented. Thus, we consider that it is possible to evaluate the liquefaction potential test based on the comparison of the results of the test and the TMLs determined by the methods described in Appendix D of the BC Code.
