1.This test uses a boring machine to present soil strength as N-value by driving a sampler into the ground for 30cm by blows from a slide hammer, and N-value resolution is per 1m so data only represents 30% of entire depth.  
 's Comment: is not actually a problem with the test, but with the method used in Japan to report the test results. In the U.S., one N-value isn't taken to represent a full one-meter interval, but only the 30 cm (or shorter) interval over which the sampler was driven. 
 's comment: I understand. This only applies to Japan, and the US civil industry analyze the ground consecutively, but the source also points out the interval is not always 30cm. This seems to be true in the US as well. And instead of deleting, one could point out this as the problem of the Japanese civil industry.  

 2. Measured data are neither linear scaling nor normal distribution, but logarithmic normal distribution. 
 's Comment: doesn't actually mean anything - there's a difference between a "scaling" and a "distribution".  
 : Soil strength is very wide ranged from the N-value zero to super hard rock, and if the researchers would like to be able to analyze the wide range of data, the scale needs to be exponential. 

 3. The method employees such a primitive method counting a number of blows of a slide hammer, it cannot collect accurate data for weak soil layers. 
 's Comment: The primitiveness of the method is not *why* it is inaccurate for weak soils. 
 's comment: The source does not use the term “primitive.” The source says “Problematic N-value zero.” But the hammer uses the accelerated force, and strong force tends to drive away everything.  
 One can tell that there is a great difference in how the force is applied to a matter using a sledgehammer pounding or using a drill and slowly squeezing out. The results are limited to whole numbers for a specific driving interval. This is very true, and the use of sledgehammer is the source of the problem. 
 In this 21st century or the high-tech century, is the use of sledgehammer and counting the blows the most sophisticated method to analyze the delicate and sensitive matter such as the ground?  This is why I used *primitive.* 

 From here is based on other document, but it does support my point. 
 Even if SPT N-value is consecutively measured, the sledgehammer drives in the sampler with acceleration. At the presence of gravels easily crackable by the boring machine, the N-value will be the average of the gravels and that location.  If the gravel is relatively strong, the blow will be consumed with the gravel's entire surface area so at the weak layer the entire surface area of the gravels will be measured, and the resulting N-value will be bigger even at the presence of the weak layer. 

 A sliding layer that would cause a landslide is a couple of centimeter thickness and slide with water so one cannot detect the sliding layers with the standard penetration method. 

 Recently there have been many landslides due to this reason; with the boring machine it is very hard to detect this sliding layers. Especially, the method cannot detect 0 to 3 N-value weak layers. 

 Some words could have been strong, but I do not believe they were wrong at all. 
 I believe the discussion is essential to improve everything. I welcome feedback. Thank you. 

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 ==Further discussion==