engleski

Liquid limit – reliable indicator of the shear strength and its influence on sliding hazard.

The laboratory determinations of the liquid limits with the application of the RNK method give very correct prognosis of the shear strength and its spatial distribution. Liquid limit is a good indicator of the “sliding potential” and its influence on the sliding hazard. The article presents the correlation diagram of the peak and residual friction angle with the liquid limit of the natural soils and the soft rocks as well as the way of its practical appplication. Connecting the series of the correlation geotechnical columns of particular sites, in the particular zones of different lithostratigraphic units, with the produced preliminary landslide hazard map of the pilot area, the idea of correct evaluation of the influence of the ''sliding potential'' over the liquid limit size, as one of the basic factors of sliding risks, is presented. The corresponding directives and suggestions for the practical usage of the liquid limit, as the perfect indicator of the shear strength and the ''sliding potential'' in making the landslide hazard maps, are given. In the study of landslides, stability levels of natural slopes, and artificially shaped slopes, unequivocal results can be obtained by the correlation of formations, and this by introducing the reference level of correlation (RNK-method) and by looking for the zone of minimum shear strength in the engineering-geological and geotechnical correlation column through the plasticity index. Properly verified examples fully confirms significance of establishing engineering-geological and geotechnical correlation columns, particularly in the case of smaller areas. However, such column can sometimes be established for zones occupying as much as several square kilometres in area. The slip-plane positioning logic is confirmed by all segments and details studied in the scope of this analysis. When applied strictly and accurately, the methodology can be used widely under appropriate geological circumstances in soft rocks and in all types of soil. Results obtained so far prove that the method is fully suitable for the preparation of exact engineering-geological and geotechnical models, and that such use of the method is highly recommended. Its qualities are best manifested in the case of lithologically monotonous pelitic sediment profiles (silt and clay mixtures and their alternations), both in cases when the limits between individual formations can or cannot be clearly distinguished. The research results presented in the paper are the best recommendations for RNK-method for its use in geotechnical microzonation slopes, according to the criteria of stability (landslide susceptibility, hazard and risk maps). In the already urbanized areas, this maps must be inevitably based on correctly specified geotechnical boundary conditions. Liquid limit is confirmed as reliable indicator of the shear strength and its influence on sliding hazard. Because of this, it is possible, by a numerous laboratory testings of liquid limit only, to form correct correlational geotechnical columns. It is very important to significantly lower the costs of the whole making process of described maps for larger areas.

Liquid limit; plasticity index; shear strength indicator; RNK method; sliding hazard

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