Rock strength criteria
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It is not clear exactly how a rock fails, either in terms of the precise details of each micro crack initiation and Propagation or in terms of the total structural breakdown as many micro cracks propagate and coalesce. In both cases, the... more
It is not clear exactly how a rock fails, either in terms of the precise details of each micro crack initiation and Propagation or in terms of the total structural breakdown as many micro cracks propagate and coalesce. In both cases, the process is extremely complex and not subject to convenient characterization through simplified models. Nevertheless, as engineers, we should like some measure of the failure properties and the ability to predict when failure will occur. The strength criteria of rock materials can be divided into three major groups: theoretical failure criteria, experimental and curve fitting based criteria. And the last set of them is composed of two mentioned sets of failure criteria. The Mohr-Coulomb criterion expresses the relation between the shear stress and the normal stress at failure. The plane Griffith criterion which locates in theoretical group, express the uniaxial tensile strength in terms of the strain energy required to propagate micro cracks. One of the most widely used empirical strength criterion for intact rock and rock masses is Hoek-Brown Criterion. In this paper we present outlines of these criteria and focus on the Hoek-Brown criterion. The method of research is based on books and articles published in authoritative publications and journals. As a result, various types of rock failure criteria are classified and some useful suggestions regarding presented criteria have been presented. Empirical criteria, Specially Hoek and Brown Criterion, Which are in good correlations with real conditions, can be significantly much more efficient in the rock mechanics problems.
Представлены результаты сопоставительных расчетов деформаций бетона по наиболее разработанным деформационным теориям для случаев простых и сложных режимов одно, двух и трехосного нагружения. Приведены основные соотношения... more
Представлены результаты сопоставительных расчетов деформаций бетона по наиболее разработанным деформационным теориям для случаев простых и сложных режимов одно, двух и трехосного нагружения. Приведены основные соотношения модифицированного варианта деформационной теории пластичности бетона, разрабатываемого в ДонНАСА. Бетон представлен моделью ортотропного тела, ортотропные свойства которого обусловлены направленным развитием микроразрушений в структуре, проявляющихся в виде эффектов сжимаемости и дилатации. В работе рассмотрены данные экспериментальных исследований в условиях пропорционального и непропорционального двух и трехосного сжатия. Выполнена оценка соответствия расчетных величин с опытными. Показа но, что соотношения деформационной теории пластичности бетона и ее модифицированного варианта в общем случае применимы для описания деформаций бетона при различных программах сложного (непропорционального) двух и трехосного возрастающего нагружения без разгрузки. Определен как наиболее перспективный для последующего развития вариант модифицированной деформационной теории пластичности бетона на основе сдвиго-отрывной модели разрушения его структуры. Дальней шее развитие ортотропной модели требует проведения специальных экспериментов для количественной оценки составляющих деформаций, обусловленных процессами микроразрушений в структуре бетона.
[The results of comparative calculations of concrete strains by the most developed deformation theory for the cases of simple and complex modes of one, two and triaxial loading are presented. The basic ratios for the modified version plasticity deformation theory for concrete developed in DonNACA are given. Concrete is presented by the model of an orthotropic solid, orthotropic properties of which are caused by directed development of structure micro fractures, which appear as the effects of compressibility and dilatation. The paper discusses the results of experimental studies in conditions of proportional and non proportional two and triaxial compression. Conformity of agreement between the calculated values and the experimental one has been performed. It is shown that the ratio of the concrete plasticity strains theory and its modified version, in general, can be used for the description of concrete deformation under various programs of a complex (nonproportional) two and triaxial increasing loading without unloading. The modified version of concrete plasticity deformation theory based on the shear rupture fracture model of concrete structure was founded the most promising for further development. The orthotropic model further development require special experiments for the quantitative assessment of deformation components which are caused by the micro fracture processes in the concrete structure.]
[The results of comparative calculations of concrete strains by the most developed deformation theory for the cases of simple and complex modes of one, two and triaxial loading are presented. The basic ratios for the modified version plasticity deformation theory for concrete developed in DonNACA are given. Concrete is presented by the model of an orthotropic solid, orthotropic properties of which are caused by directed development of structure micro fractures, which appear as the effects of compressibility and dilatation. The paper discusses the results of experimental studies in conditions of proportional and non proportional two and triaxial compression. Conformity of agreement between the calculated values and the experimental one has been performed. It is shown that the ratio of the concrete plasticity strains theory and its modified version, in general, can be used for the description of concrete deformation under various programs of a complex (nonproportional) two and triaxial increasing loading without unloading. The modified version of concrete plasticity deformation theory based on the shear rupture fracture model of concrete structure was founded the most promising for further development. The orthotropic model further development require special experiments for the quantitative assessment of deformation components which are caused by the micro fracture processes in the concrete structure.]