Mechanism Of Brittle Fracture Of Rock

This text comprises different basic aspects of brittle failure for rocks. It considers classical and contemporary models, as well as failure patterns under different loading schemes.

Much of the research on fracture of rocks or rock-like materials conducted over the past two decades may be considered as "academic studies" of the general phenomenon of fracture. Yet, the understanding of this phenomenon is fundamental if a material is used in any engineering design, whether the aim is to prevent failure of the structure or to promote it. Fracture theories existing are generally empirical and derived from experimental results of laboratory test with simple boundary conditions. Because of the basic weakness of rock intension and because in general the environmental stresses in rock mechanics are compressive most of these theories consider fracture under compressive stress conditions. The Coulomb-Navier-, the Mohr-, the Griffith and the McClintock and Walsh criteria are typical examples and will be considered in the following. In addition the tendency during the past was in making accurate experiments under conditions of homogeneous stresses. To obtain information about the fracture behaviour with unequal principal stresses systems have to be used which involve inhomogeneous stresses. This case is of particular interest, since in practical rock mechanics we may expect conditions of highly inhomogeneous stresses. However, a consideration of such situations involve additional assumptions like the applicability of the theory of elasticity for calculating the stress field, which may be open to question. A distinction has to be made between fracture initiation and fracture propagation, since a detailed observation of the total fracture process in rock was possible by means of "stiff" and "servo-controlled" loading systems.

This volume presents the proceedings of a symposium on rock mechanics, held in the USA in 1995. Topics covered include: rock dynamics; tool-rock interaction; radioactive waste disposal; underground mining; fragmentation and blasting; theoretical and model studies; hydrology; and rock creep.

"This book emphasizes the physical and practical aspects of fatigue and fracture. It covers mechanical properties of materials, differences between ductile and brittle fractures, fracture mechanics, the basics of fatigue, structural joints, high temperature failures, wear, environmentally-induced failures, and steps in the failure analysis process."--publishers website.

This book presents the theoretical concepts of stress and strain, as well as the strengthening and fracture mechanisms of engineering materials in an accessible level for non-expert readers, but without losing scientific rigor. This volume fills the gap between the specialized books on mechanical behavior, physical metallurgy and material science and engineering books on strength of materials, structural design and materials failure. Therefore it is intended for college students and practicing engineers that are learning for the first time the mechanical behavior and failure of engineering materials or wish to deepen their understanding on these topics. The book includes specific topics seldom covered in other books, such as: how to determine a state of stress, the relation between stress definition and mechanical design, or the theory behind the methods included in industrial standards to assess defects or to determine fatigue life. The emphasis is put into the link between scientific knowledge and practical applications, including solved problems of the main topics, such as stress and strain calculation. Mohr's Circle, yield criteria, fracture mechanics, fatigue and creep life prediction. The volume covers both the original findings in the field of mechanical behavior of engineering materials, and the most recent and widely accepted theories and techniques applied to this topic. At the beginning of some selected topics that by the author's judgement are transcendental for this field of study, the prime references are given, as well as a brief biographical semblance of those who were the pioneers or original contributors. Finally, the intention of this book is to be a textbook for undergraduate and graduate courses on Mechanical Behavior, Mechanical Metallurgy and Materials Science, as well as a consulting and/or training material for practicing engineers in industry that deal with mechanical design, materials selection, material processing, structural integrity assessment, and for researchers that incursion for the first time in the topics covered in this book.

When dealing with rock in civil engineering, mining engineering and other engineering, the process by which the rock fails under load should be understood, so that safe structures can be built on and in the rock. However, there are many ways for loading rock and rock can have a variety of idiosyncracies. This reference book provides engineers and researchers with the essential knowledge for a clear understanding of the process of rock failure under different conditions. It contains an introductory chapter explaining the role of rock failure in engineering projects plus a summary of the theories governing rock failure and an explanation of the computer simulation method. It subsquently deals in detail with explaining, simulating and illustrating rock failure in laboratory and field. The concluding chapter discusses coupled modelling and the anticipated future directions for this type of computer simulation. An appendix describing the RFPA numerical model (Rock Failure Process Analysis program) is also included. About the Authors Chun'an Tang has a PhD in Mining Engineering and is a Professor at the School of Civil & Hydraulic Engineering at Dalian University of Technology in China. He is an advisor for design and stablity problem modelling in mining and civil rock engineeringand and Chairman of the China National Group of the International Society for Rock Mechanics. John Hudson is emeritus professor at Imperial College, London and is active as an independant consultant for Rock Engineering Consultants. He has a PhD in Rock Mechanics and completed over a 130 rock engineering consulting assignments in mining and civil engineering. He is a fellow at the Royal Academy of Engineering in the UK and President of the International Society for Rock Mechanics.

This monograph deals with the part of the field of ex-' perimental rock deformation that is dominated by the phenomena of brittle fracture on one scale or another. Thus a distinction has been drawn between the fields of brittle und ductile behaviour in rock, corresponding more or less to a distinction between the phenomena of fracture and flow. It is hoped eventually to present a survey of the ductile field in a separate volume. The last chapter of this volume deals with the transition between the two fields. The scope of this survey has been limited to the mec.hanical properties of rock viewed as a material on the laboratory scale. Thus, the topic and approach is of a "materials science" kind rather than of a "structures" kind. We are dealing with only one part of the wider field of rock mechanics, which also includes structural or boundary value problems, for example, those of the stability of slopes, the collapse of mine openings, earth quakes, the folding of stratified rock, and the convec tive motion of the earth's mantle. One topic thus ex cluded is the role of jointing, which it is commonly necessary to take into account in applications in engi neering and mining, and probably often in geology too.