Penetration Test using the small vessel is 10 mm, maximum grain size was defined as 9.5 mm for materials other than coals. In other words, particles which are larger than 9.5 mm should be removed from samples by sieving.
Considering that the maximum grain size of coals for the Penetration Test is 25 mm. maximum grain size of coals for the measurement of grain size distribution was defined as 19.0 mm
The criteria of D10 on liquefaction were investigated under the aforesaid condition for maximum grain size.
3.3 Criterion of grain size distribution of the materials other than coals
3.3.1 Preparation of the samples and their grain size distribution
For the investigation, two slags, i.e., Nickel Slag and Copper Slag, were prepared. Before the commencement of the liquefaction potential test, the samples having various grain size distributions were prepared by the following procedure:
(1) Sieve the material;
(2) Plot the grain size accumulation curve;
(3) Define new grain size accumulation curves, and
(4) Prepare the samples according to the defined curves by blending the sieved particles.
Because the materials as received were too coarse to contain high moisture, new grain size accumulation curves were defined by increasing the quantity of fine particles as shown in Figure 3 and 4
3.3.2 Results of liquefaction potential test
The results of the liquefaction potential test for the aforesaid samples are shown in Table 1. It can be said that D; = 0.5 mm corresponds to 70 % degree of saturation. Taking safety factor into consideration, the proposed criterion of D10 is concluded as 1 .0 mm for materials other than coals.
3.4 Criterion of grain size distribution for coals
By the Penetration Test, it is judged whether the moisture content of a sample is less than Flow Moisture Point (FMP) or not. The criterion of D10 for coals was, therefore, investigated through the Penetration Test using some samples having moisture content as high as possible in various grain size distributions. 3.4.1 Preparation of the samples and their grain size distribution
Figures 5 and 6 show the grain size accumulation curves of the samples from two mines. prepared by the similar sieving and blending process in paragraph 3.3.1.
3.4.2 Moisture content for the tests
Because the purpose of the research is to determine the criterion under ordinary drained condition, the moisture contents of the samples for the tests were adjusted as high as possible under the drained condition by the following procedure:
(1)Prepare a dry sample in a shallow water-tight box;
(2)Pour water into the sample and stir the sample so as to be uniform;
(3)Gather the sample to one side in the box and tilt the box slightly; and
(4)Repeat (2) and (3) until the water significantly drains from the sample.
3.4.3 Results of Penetration Test
The results of the tests are shown in Table 3. According to the criterion of the Penetration Test, it is judged that liquefaction did not take place when the penetration depth is less than 50 mm. Thus the liquefaction potential of each sample can be judged as shown in the table.
Based on the results, it can be said that D,o 1.4 mm is the lower limit of grain size distribution of materials which can be evaluated as not liable to liquefy. Taking safety factor
