STUDY OF COMPATIBILITY OF METHODS FOR LIQUID LIMIT MEASUREMENT ACCORDING TO CZECH STATE STANDARD AND NEWLY ADOPTED EUROPEAN STANDARD STUDIE KOMPATIBILITY METOD PRO MĚŘENÍ VLHKOSTI NA MEZI TEKUTOSTI DLE ČSN A NOVĚ PŘIJÍMANÉ EVROPSKÉ NORMY
The goal of the publication is a correlation between the methodology of liquid limit determination using Casagrande bowls according to the Czech state standard being valid as yet and the methodology on a principle of the conical test according to a newly adopted European standard. It allows a better link of utilization of an extensive statistical set of investigations realized for purposes of foundation engineering in past that are available in Geofond for newly conducted engineering geological studies according to the new European standard related to water contents at the liquid limit for wide-spread clay soils. The sample values ranged from 21.49 to 49.56 % according to Casagrande and in the conical test they ranged from 24.11 to 51.07 %. The difference of the results for identical samples reached values from 1.15 to 4.19 %. The studied mean difference coefficient between methods amounts to 2.55 %.
Comparison between Casagrande and drop-cone methods to calculate liquid limit for pure clay
Spagnoli, G. 2012. Comparison between Casagrande and drop-cone methods to calculate liquid limit for pure clay. Can. J. Soil Sci. 92: 859-864. During the construction of international projects off German coasts, it often occurs that clients and contractors work according to different standards. The aim of this experimental research is to compare the results of DIN and BS standards. The liquid limits of 50 pure kaolinitic and illitic clays were tested according to the German (Casagrande cup hard base) and the British (cone penetrometer) standards. Previous works were performed on natural clayey soils, while the research proposed in this work is based on tests carried out on standard pure clays. Illitic and kaolinitic clay types were chosen since they are abundant in the sediments of the Baltic Sea and North Sea where several offshore wind park projects are currently under construction or planned. The results show that the values obtained with the German Casagrande cup are slightly lower than those obtained with the British cone penetrometer. A regression equation was obtained to compare the liquid limit according to DIN and to BS for pure non-swelling clays namely LLcone=0.99 LLcup+1.05. The obtained relation agrees very well with other previous works.
De Natura Lutorum
Despite recent advances in clay mineralogy there is still no generally accepted definition of the terms clays and clay minerals. This problem is discussed from the historical aspect: the similarities of definitions given from the 16th century to the present are remarkable and lead one to consider whether possible simple modifications might not eventuate in some measure of universal agreement. Comparison of nomenclature and classification schemes shows that from the time of Theophrastus to that of Agricola there appears to have been little advance, but a change becomes noticeable by the end of the 18th century, and by the end of the 19th old names, such as porcelain clay, etc., have given place to what are now regarded as names of mineral species or varieties. Only after the 1920’s have satisfactory groupings been obtained, but no internationally acceptable classification has yet been devised. Finally, the various factors operative during clay formation by weathering and diagenesis are discussed, and it is stressed that field and laboratory studies are complementary.