Wpływ litogenezy na fizyczno-mechaniczne właściwości lessów określane metodami polowymi

Zbigniew Frankowski

Abstract


THE INFLUENCE OF LITHOGENESIS ON PHYSICO-MECHANICAL PROPERTIES AS DETERMINED BY FIELD METHODS

Summary
The article presents the results of in situ investigations south Poland loesses. The physical and me chemical properties of loesses were determined using radiometric and electric methods, static sounding, vane test and Menard's pressuremeter. The variability of physico-mechanical properties with depth has been shown on the basis of the results obtained. Due consideration has been given to geologic-engineering properties of loesses in profiles showing a distinct lithologic-stratigraphical differentiation. Three horizons most important from the lithogenetic point of view have been distinguished on the basis on the following features: grain size distribution, carbonate content, total porosity texture and colour. These horizons have been characterized by selected physico-mechanical properties. The effect of various physical properties, especially natural moisture, on the strength parameters has been analyzed.
Criteria of evaluating collapsing loess defined by various methods have been discussed. It has been shown that degree of saturation below 0.6 and void ratio over 0.72 are the preliminary criteria in evaluation of collapsing of loesses. In situ investigations carried out with the use of pressuremeter gave a new, more precise criterion. The new criterion of collapsing of loesses, based on the difference between the pressuremeter limit pressure PL and the creep pressure Pf is given by formula: PL – Pf ≤ 0.21 MN/m2 and may be obtained without laboratory tests.

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