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National Academy of Engineering, and provides studies and reports on problem areas in rock mechanics of concern to federal and state agencies, industry, and the rock mechanics community in general. Now, again, let me ask each of you to join in efforts of this committee...really it is your society, your National Committee for Rock Mechanics. It could well lead into a National Society for Rock Mechanics. That really, I think, is the basic hope of most of us, a society that we can all identify with, practicing the new science of rock mechanics. Thank you very much.
by Pierre Habib
President of the International Society for Rock Mechanics.
As this 16th Symposium on Rock Mechanics ends we can all reflect that it has been a great success. Any industrial activity involves the three phrases
i) Measurement of material properties,
iii) Construction, and the feedback between them. At this symposium we have seen that rock mechanics involves various kinds of design. There are civil engineering situations in which computer aided design is completed before construction. Conversely, tunnels are often best designed as new information comes to light during construction. Some years ago we even had the unfortunate situation that a correct design often could only be made after construction. Here we have been privileged to see contributors from many different countries demonstrate impressive improvements in practical design techniques, indicating a genuine interest in making intellectual contracts with fellow practitioners in other parts of the world. We must thank the Department of Civil and Mineral Engineering of the University of Minnesota for hosting the Symposium, and Charles Fairhurst and Steven Crouch for undertaking the heavy task of planning it. On behalf of the International Society for Rock Mechanics, I wish to thank them both. For each of you, the participants, I' hope that knowledge gained in the last three days will be of benefit in your future professional work.
Brittleness characterizes the mechanical behavior of stiff soils, such as overconsolidated clays and cemented sands. Although there is no single reason for this behavior, many researchers have called attention to the fact that the presence of flaws—i.e. fissures, cracks, joints—has a great effect on the strength and overall stress-strain behavior of such materials. These defects result in stress concentrations that lead to local failure and reduction in the overall strength of the material as the failure propagates through the intact region. This phenomenon shows that the failure mechanisms of earth structures, such as slopes in cemented sand, are different from traditional shear failure. In other words, conventional analysis techniques based on classical strength criteria might not be adequate. To represent failure phenomena, fracture mechanics can appropriately be adopted as a tool for analysis of these materials. However, the use of fracture mechanics concepts, especially for cemented sands, is faced with difficulties in obtaining relevant parameters, because fracture parameters and predictions are highly dependent on the material constituents and specimen size as well as particle size. Four-point beam bending tests were conducted involving specimens of 3 different sizes and 3 different grain sizes. Through these techniques, we found that the fracture behavior of cemented sands is greatly dependent on both the grain size of the constituent material and the size of the specimens.
When engineers encounter design and analysis challenges involving natural and man-made slopes, shallow and deep foundations, and deep excavations in stiff or brittle soils, they often observe that the shear stresses at failure are much smaller than the shear strength obtained from traditional laboratory experiments and basic limit equilibrium analysis (Lo, 1972). Plus, the failure mechanism is often very different from the classical limit plasticity, characteristics and limit equilibrium mechanisms with which geotechnical engineers are familiar.
For several years, a series of highly successful one-year post-graduate Courses in Geotechnical Engineering have been taught at Imperial College, London. These professionally oriented Courses provide specialist training in Engineering Geology, Engineering Rock Mechanics, Engineering Seismology, and Soil Mechanics. This paper describes the objectives, development and present organization of these Courses. A significant feature of this organization is that, although the Courses are sponsored by three different Departments within the College and each Course has its own special characteristics, the four programmes are closely co-ordinated to permit efficient treatment of the considerable amount of common ground between them.