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The implementation of projects for the construction of high-speed railways actualizes the search of effective approaches to accounting the influence of soil strata heterogeneity along the course of the track on differential foundation settlements of overpasses. Russian special technical conditions prescribe sufficiently stringent regulation limits of absolute values of overpasses' foundation soil settlements (20 mm for ballastless track) and angles of break in profile (the differential foundation soil settlement), which should not exceed 1 ‰ for ballastless track. These requirements make it necessary to develop the calculation method, which is based on the criterion of deformation. To ensure compliance of design solutions to the specified regulations it is appropriate to use the method of the predefined equated soil settlements for design of shallow foundations of overpasses for high-speed railways. Several features of application of this method are presented in this article.

Статья посвящена разработанной методике расчѐта фундаментов мелкого заложения на естественном основании по заданной осадке, преимуществами которой являются: обеспечение наилучших условий функционирования надземных конструкций за счѐт уменьшения неравномерности осадок фундаментов до минимально допустимого значе-ния, снижение ресурсозатрат на устройство фундаментов за счѐт использования стадии нелинейного деформирования грунта. Изложены основные положения и допущения предлагаемой методики. Представлены результаты лотковых штамповых испытаний, на основе которых определены поправочные коэффициенты. Произведѐн сравнительный анализ полученных экспериментальных данных и результатов расчѐтов по различным методикам определения осадки, который показал удовлетворительное для инженерного подхода совпадение результатов при давлении до 0,7 от предельного, что подтверждает корректность принятых допущений.Ключевые слова: расчѐт деформации; осадка фундамента; инженерный ме-тод; фундамент мелкого заложения; фундамент на естественном основании. S.I. ALEKSEEV, S.O. KONDRAT'EV, Emperor Alexander I St. Petersburg State Transport University SPREAD FOUNDATION CALCULATION ACCORDING TO PREDETERMINED SETTLEMENTPurpose: The aim of this work is to improve the functioning conditions for building superstructures due to non-uniformity minimization of spread foundation settlements down to its ultimate value. Design technique: The main conditions and assumptions of the proposed design technique for shallow spread foundation calculation according to a given settlement are based on the analytical method. Settlement correction indices for the nonlinear stage of soil deformation are obtained experimentally in trough plate bearing tests. Findings: The reduction in the settlement non-uniformity of shallow spread foundations is provided by the proposed design technique Методика проектирования фундаментов на естественном основании 195 which involves rather accurate analysis of foundation settlements. At the initial design stage of sizing the settlement, the non-linear soil deformation is used to provide the extension of the settlement value range. A nonlinearity factor of the elasto-plastic foundation is used to determine its settlement at a given stage of soil deformation. This factor is obtained from the volume change trajectory of the yielding area calculated with the following assumptions. For the linearly deformed half-space, the boundary of applicability is 1.1 of the initial critical soil pressure; when the foundation achieves the ultimate pressure (according to Coulomb's wedge theory), the yielding area volume also achieves a certain ultimate value; the foundation transition to the ultimate limit state is a complex, random process. Examination of the physical nature in the soil deformation analysis is improved by a transition from a piece-wise approximation of the dependence between the foundation base pressure and yielding area volume to the continuous function and the initial critical soil pressure introduced as a phase transformation criteri...