Örnek hazırlama yönteminin likit limit ve plastik limit değerlerine etkisi

Bu çalışmada, örnek hazırlama yönteminin likit limit ve plastik limit değerleri üzerindeki etkisi araştırılmış olup, ASTM D 4318-00’de tanımlanan yöntem (standart yöntem) ve ülkemizdeki bazı laboratuvarlarda uygulanan örnek hazırlama yöntemiyle (standart olmayan yöntem) hazırlanmış örneklerin likit limit ve plastik limitleri karşılaştırılmıştır. Bu amaçla, Türkiye’nin değişik bölgelerinden alınmış ve likit limiti % 30 ile % 90 arasında değişen 30 adet doğal zemin örneği kullanılmıştır. Örneklerin likit limitleri hem Casagrande, hem de koni batma yöntemiyle belirlenmiştir. Elde edilen deney sonuçları, standart yöntemle hazırlanmış örneklerin likit limitlerinin, standart olmayan yöntemle hazırlanmış örneklerin likit limitlerinden, Casagrande yönteminde % 10’a, koni batma yönteminde ise % 8’e kadar daha yüksek olduğunu göstermiştir. Standart yöntemle hazırlanmış örneklerin plastik limitlerinin ise, standart olmayan yöntemle hazırlanmış örneklerin plastik limitlerinden en fazla % 3’e kadar daha yüksek olduğu belirlenmiştir. Likit limit ve plastik limit değerleri arasında, örnek hazırlama yönteminden kaynaklanan farkın, örneklerin USCS’ye göre belirlenen zemin sınıflarının değişmesine de yol açabileceği saptanmıştır.

Effect of sample preparation method on the liquid limit and plastic limit values

In this study, the effect of sample preparation method on the liquid limit and plastic limit values was examined. For this purpose, the liquid limit and plastic limit values of the samples, which have been determined by dry preparation method defined in ASTM D 4318-00 (standard method) and the method followed by some laboratories in Turkey (non-standard method) were compared. In the study, 30 natural soil samples with a liquid limit values ranging between 30% and 90% taken from various locations of Turkey were used. The liquid limit tests were carried out by both Casagrande and cone penetration methods. Test results indicate that the liquid limit values of the samples prepared by standard method are greater than those of the samples prepared by the non-standard method, up to 10 % in the Casagrande method and up to 8 % in the cone penetration method. The plastic limit values of the samples which were prepared by the standard method are greater than those of the samples prepared by the non-standard method up to 3 %. It was also observed that the soil type of the some samples according to USCS may be altered due to differences of the sample preparation method.

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