Effect of Intermediate Principal Stress on the Bearing Capacity of Footings in Soft Rock

The bearing capacity for footings is a fundamental scientific problem in civil engineering. The evaluation of the bearing capacity of footings usually does not take into account the effect of the intermediate principal stress. In practice, the intermediate principal stress has certain influences on the strength of geomaterials (e.g., rock and soil) or concrete. In this paper, a series of numerical solutions are presented to evaluate the bearing capacity of footings in a soft rock foundation via a two-dimensional finite difference code (FLAC) with a strain hardening/softening constitutive model based on the unified strength theory (UST). The values of the bearing capacity factor Nc and Nγ for strip, circular and square footings in a soft rock foundation were evaluated using the strain hardening/softening constitutive model. The effect of the intermediate principal stress on the bearing capacity of strip, circular and square footings in a soft rock foundation was analyzed. The results of the numerical computation show that the intermediate principal stress has a significant influence on the bearing capacity and failure mechanisms of a soft rock medium. The influence of the intermediate principal stress on the peak and residual values of the bearing capacity for a strip footing is much greater than for circular and square footings. Research works for the reasonable estimation of the bearing capacity of footings in soft rock are facilitated by this study.

Application of gas-magnetic bearings in turbine compressors of marine ICE pressurizing systems

В статье приводится обоснование применения газомагнитных подшипников в судовых турбокомпрессорах систем наддува дизелей. Показаны отрицательные стороны применения наиболее распространенных подшипниковых узлов с масляной системой смазки. Для подтверждения эффективности применения газомагнитных опор в турбокомпрессорах необходимо провести целый ряд исследований. Первым шагом исследований явилось определение и изучение основных эксплуатационных характеристик газомагнитного подшипника – коэффициентов несущей способности и жесткости смазочного слоя. В качестве методов исследования использовался теоретический анализ и физический эксперимент, для реализации которых были разработаны методика расчета, в основе своей базирующаяся на решении модифицированного уравнения Рейнольдса теории газовой смазки, и экспериментальный стенд для исследования эксплуатационных характеристик радиальной газомагнитной опоры. Результаты сравнительного анализа экспериментальных и теоретических характеристик показали на их вполне удовлетворительное согласование, что позволяет в дальнейшем проведение широкомасштабные теоретических исследований. The article gives a justification for using gas-magnetic bearings in marine turbine compressors of diesel engine pressurizing systems. The drawbacks of using the most common bearing units with oil lubrication are shown. A number of studies is required to confirm the efficiency of using gas-magnetic bearings in turbine compressors. The first step is to determine and study the main operational characteristics of a gas-magnetic bearing: bearing capacity factor and lubricating film stiffness. The study methods included theoretical analysis and a physical experiment. A calculation method has been developed for their implementation based on the solution of the modified Reynolds equation from gas lubrication theory and a test bench for studying operational characteristics of a radial gas-magnetic bearing. The results of comparative analysis of experimental and theoretical characteristics has shown that they correspond well which allows performing future large-scale theoretical studies.

The comparison study of the monopole tower foundation using CPT and laboratory data in Gresik district, East Java-Indonesia

In the millennial era, the development of information and communication technology is very fast, one of the telecommunications infrastructure is a monopole type telecommunications tower. This type of tower is one of 3 types of telecommunication towers whose main construction is made of steel. The monopole structure is supported by a tread foundation, which is one type of shallow foundation. The main factor in the design of the tread foundation is the bearing capacity factor. Calculation of foundation bearing capacity can be done directly in the field using Sondir data (CPT) and indirectly using laboratory data. In this study a study was conducted to compare the carrying capacity of monopole foundations between field data methods in the form of Sondir data or CPT with result data. Soil tests in the laboratory calculated with the Terzaghi formula. The research location was carried out in Gresik Regency, East Java Province, Indonesia at 3 sites, namely: Mojosarirejo, Kembangan Kebomas and Setromenganti. The results of the comparison of the calculation of the bearing capacity of the foundation (Q) at the Mojosarirejo site with the type of sandy soil. value of QSondir < 9.58 % of Qterzaghi. At the Krembangan Kebomas site with brown clay and gravely clay, the Q value was < 69.93 % of the Qterzaghi and at the Setromenganti site with brown clay soil type with the influence of water level depth – 1 m, the Q value was < 27, 62% of Qterzaghi. From the comparison of the average calculation in the 3 study locations, the bearing capacity of QSondir treads foundation is 26.50 % smaller than Qterzaghi, so the use of Sondir data is more accurate for use in tread foundation planning and provides greater security assurance for the tower foundation structure. monopole type

Model experiments to assess effect of cavities on bearing capacity of two interfering superficial foundations resting on granular soil

The objective of this paper is to describe the effect of cavities on the bearing capacity of two interfering footings based on granular soil using an exclusively experimental approach with a test model designed in the laboratory. The experimental protocol was carried out based on the variation of several parameters such as the spacing (x) (axis to axis) between the footings, and the distance (H) between the footings and cavities and between the cavities axes (L). The results highlight the effect of cavities and the interference of two strip footings on the bearing capacity factor (q) and efficiency factor (EF). Moreover, the results revealed that, in the case wherein the distance between the footings and the cavity is greater than 3, the cavity impact is eliminated.