Improvement of methods of constructing pile foundations in permafrost soils

This article discusses peculiarities of constructing pile foundations in permafrost soils in different natural, technical, and economic conditions. Examples are given of the most efficient use of combined methods of setting ready-made and precast monolithic piles. Scientific Research Institute of Foundations and Underground Structures. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 28–30, July–August, 1994.     

Sulfhydryl groups of alpha-actinin

It has been established that the molecule of alpha-actinin (m. w. 200 000) contains 16 SH-groups, which are distinguished by their activity. Six SH-groups may be comparatively easily discovered in the native protein. Four partly "masked" SH-groups are titrated in the low acidic media. Five-six SH-groups are completely masked and are revealed only after denaturation of protein. Blocking of SH-groups of alpha-actinin by the parachloromercuribenzoate decreases the biological activity of alpha-actinin measured by the formation of the alpha-actinin--actin complex. It has been shown that partly "masked" SH-groups revealed with the temperature increase are not incorporated into the active centre and do not take part in protein functioning.     

BRITTLENESS OF ORGANIC BINDERS AFTER REPEATED TENSION AT NEGATIVE TEMPERATURES

Under real conditions of road pavement operation the films of organic binders are subjected to repeated tensile deformations, in particular, at negative temperatures. In the paper, an attempt to use Fraas apparatus not only for determining the brittleness temperature of binders but also for estimating their long-term strengths at negative temperatures under conditions of repeated tension at bending has been realized. One has investigated bitumens of BND 40/60; 60/90; 90/130 grades and polymer bitumen binders on their base with 2.0; 3.5; 5.0% of block copolymer of SBS type and of DST-30R-01 grade and 20% of plasticizer-industrial oil. For all specimens the Fraas brittleness temperature and also the temperature at which a binder layer on the metal plate cannot withstand 200 cycles of bending tension without developing a large crack have been determined. For bitumens this temperature is 5 to 7°C higher than the corresponding britteness temperature. A polymer bitumen layer withstands 200 cycles of bending tension at the temperature which is 1°C higher than the corresponding Fraas brittleness temperature. The Fraas temperature of the pre-loaded specimen decreases in specific cases by 20°C. It is shown that the crack resistance of polymer bitumen binders is significantly higher and that of bitumens is lower than it is expected according to the procedure of determining the Fraas brittleness temperature. The crack resistanse of the polymer-bitumen binder specimens in the process of loading at negative temperatures increases.     

INVESTIGATION OF RHEOLOGICAL AND PHYSICO-MECHANICAL PROPERTIES OF STRUCTURE -FORMATION COMPONENTS OF ROAD BITUMENS

ABSTRACT

This paper describes the interrelationship of the structure and properties of bitumen that are necessary for the design of high quality bituminous mixtures.     

Analysis of temperature regime of permafrost bases of structures with cold cellars taking into account their preliminary cooling

Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 5–7, September–October, 1990.