Fracture mechanics has been used for many years to study the mechanical behavior of brittle and quasi-brittle materials like concrete, rock, wood, and ceramics. To date, the application of fracture mechanics to soils has been limited to dry and partially saturated soils where soil consistency changes due to suction and tends to be harder exhibiting a quasi-brittle behavior. Of late, studying fracture propagation in clays and mudrocks has become of interest as it provides a means to extract oil from oil bearing strata. While crack initiation in soils can be analyzed using basic soil mechanics theories, development and propagation of a crack is energy driven and requires application of fracture mechanics principles. An essential parameter in Linear Elastic Fracture Mechanics (LEFM), the main analytical tool in studying fracture in rock, is the critical stress intensity factor that defines stress concentration near a crack tip beyond which a fracture would propagate. The basic mode of crack loading can be obtained by applying a normal stress that has a corresponding opening mode of crack surface displacement, called mode-I (tensile mode), with a critical stress intensity factor termed fracture toughness, denoted by KIC. In this experimental research, KIC is measured indirectly using a modified Brazilian Test configuration where load is applied normally on flattened Brazilian disk specimens without the need to introduce a flaw into the specimen. Intact natural specimens from four different deposits; Boston Blue clay, San Francisco Bay Mud, Presumpscot Maine clay, and Gulf of Mexico clay; are tested in oven-dried state under atmospheric conditions. In addition, two Clay-like materials; molded Gypsum and Plaster of Paris; have been investigated. Based on the analysis of the test data, the relation between mode I fracture toughness and tensile strength for the six tested materials agrees to a great extent with reported trends in the literature even for different fracture toughness and tensile strength testing techniques and for wider tested range of soils, rocks, geomaterials, clay-like, and rock-like materials. However, no clear relation between mode I fracture toughness and elastic modulus or any other physical parameter was determined.

Supports the use and development of strong, fracture-resistant, and mechanically reliable ceramic materials The Fracture of Brittle Materials thoroughly sets forth the key scientific and engineering concepts underlying the selection of test procedures for fracture toughness, strength determination, and reliability predictions. With this book as their guide, readers can confidently test and analyze a broad range of brittle materials in order to make the best use of existing materials as well as to support the development of new materials. The authors explain the importance of microstructure in these determinations and describe the use of quantitative fractography in failure analysis. The Fracture of Brittle Materials is relevant to a broad range of ceramic materials (i.e., any inorganic non-metal), including semiconductors, cements and concrete, oxides, carbides, and nitrides. The book covers such topics as: Basic principles of fracture mechanics underlying brittle material tests and analysis procedures Theory and mechanisms of environmentally enhanced crack growth Fracture mechanics tests to determine a material's resistance to fast fracture Test and analysis methods to assess the strength of ceramics Methods to analyze the fracture process based on quantitative measurements of the fracture surface Effect of a material's microstructure Methods for predicting the lifetime of brittle components under stress Throughout the book, figures and illustrations help readers understand key concepts and methods. Replete with real-world examples, this text enables engineers and materials and ceramics scientists to select and implement the optimal testing methods for their particular research needs and then accurately analyze the results.

This book is an attempt to provide a comprehensive and coherent description of three widely separated aspects of clays: the science of clays; the industrial uses of clays; and the role of clays in the environment. Most of the existing literature lacks such an integrated study and this work endeavours to fill that gap. An exhaustive account of the science of clays is presented in Part I of the book, which includes the classification, origin and evolution, composition and internal structure, chemical and physical properties of clays; soil mechanics; and analytical techniques for determining clay constituents. Part II provides a comprehensive description of the applications of clays and their derivatives in various industries, while Part III describes the role of clays in the environment; the pollution caused by clay minerals; and the application of clays in order to prevent environmental hazards. A principal feature of the book is its explanation of how the structure and composition of particular clay types facilitate their specific industrial or environmental applications, thus describing the interrelationship between three widely varying aspects of clay. A number of thought-provoking questions are raised at the end of the work in order to leave readers with a better insight in this regard.

Sand, clay and rock have to be excavated for a variety of purposes, such as dredging, trenching, mining (including deep sea mining), drilling, tunnel boring and many other applications. Many excavations take place on dry land, but they are also frequently required in completely saturated conditions, and the methods necessary to accomplish them consequently vary widely. This book provides an overview of cutting theories. It begins with a generic model, valid for all types of soil (sand, clay and rock), and continues with the specifics of dry sand, water-saturated sand, clay, atmospheric rock and hyperbaric rock. Small blade angles and large blade angles are discussed for each soil type, and for each case considered the equations/model for cutting forces, power and specific energy are given. With models verified by laboratory research, principally from the Delft University of Technology, and data from other recognized sources, this book will prove an invaluable reference for anybody whose work involves major excavations of any kind.