Rock Stress And Its Measurement

Rock masses are initially stressed in their current in situ state of stress and to a lesser natural state. Whether one is interested in the extent on the monitoring of stress change. formation of geological structures (folds, faults, The subject of paleostresses is only briefly intrusions, etc. ), the stability of artificial struc discussed. tures (tunnels, caverns, mines, surface excava The last 30 years have seen a major advance our knowledge and understanding of rock tions, etc. ), or the stability of boreholes, a in the in situ or virgin stress field, stress. A large body of data is now available on knowledge of along with other rock mass properties, is the state of stress in the near surface of the needed in order to predict the response of rock Earth's crust (upper 3-4km of the crust). masses to the disturbance associated with those Various theories have been proposed regarding structures. Stress in rock is usually described the origin of in situ stresses and how gravity, within the context of continuum mechanics. It is tectonics, erosion, lateral straining, rock fabric, defined at a point and is represented by a glaciation and deglaciation, topography, curva second-order Cartesian tensor with six compo ture of the Earth and other active geological nents. Because of its definition, rock stress is an features and processes contribute to the current enigmatic and fictitious quantity creating chal in situ stress field.

With the new classification of chronic myeloproliferative disorders, and the rise of interest in molecularly targeted therapies, this timely text brings together international experts on the topic to discuss the current technologies and their implications for the treatment of patients. This title comprehensively covers chronic myeloid leukemia and Ph-negative chronic myeloproliferative disorders and is an essential resource for all practitioners in Hematologic Oncology.

Any undisturbed rock mass is subject to natural stresses inclu ding gravitational stresses due to the mass of the overburden and possibly tectonic stresses due to the straining of the earth's crust and remanent stresses due to past tectonism. Knowledge of the in situ stress field must be integrated into any rock engineering design along with general rock mass characteristics such as de for mability, strength, permeability and time dependent behavior. For example, the choice of optimum orientation and shape of deep underground caverns or complex underground works will be controlled by the orientation and the magnitude of the in situ stress @ield if it is necessary to minimize stress concentration problems. Long term variation of the in situ stress field may also help to evaluate the potential hazard of earthquake occurences. The magnitude and orientation of the stress field ata point within a rock mass can be measured but there is no known method by which the state of stress at a point can be accurately determined by instruments located remotely. In general, measurements are made inside boreholes, on outcrops or on the internal surfaces of under ground cavities. Most of the measuring techniques intentionally disturb the state of stress in the rock and then measure consequent strains and displacements. Measured strains or displacements are then related to the stresses through assumptions of material behavior. A common procedure is to assume that the rock mass is linearly elastic, isotropic, continuous and homogeneous.

Stress Field of the Earth’s Crust is based on lecture notes prepared for a course offered to graduate students in the Earth sciences and engineering at University of Potsdam. In my opinion, it will undoubtedly also become a standard reference book on the desk of most scientists working with rocks, such as geophysicists, structural geologists, rock mechanics experts, as well as geotechnical and petroleum en- neers. That is because this book is concerned with what is probably the most pe- liar characteristic of rock – its initial stress condition. Rock is always under a natural state of stress, primarily a result of the gravitational and tectonic forces to which it is subjected. Crustal stresses can vary regionally and locally and can reach in places considerable magnitudes, leading to natural or man-made mechanical failure. P- existing stress distinguishes rock from most other materials and is at the core of the discipline of “Rock Mechanics”, which has been developed over the last century. Knowledge of rock stress is fundamental to understanding faulting mechanisms and earthquake triggering, to designing stable underground caverns and prod- tive oil fields, and to improving mining methods and geothermal energy extraction, among others. Several books have been written on the subject, but none has atte- ted to be as all-encompassing as the one by Zang and Stephansson.

Topics covered in these papers include: methods for rock stress measurement; interpretation of rock stresses; interpretation of rock fracture phenomena; state of stress in the Earth's crust; and applications of rock stress measurements in mining and civil engineering.

Understanding in-situ rock stress is important in the exploration and engineering involving rock masses for mining, hydropower, tunneling, oil and gas production, and stone quarrying. Traditional methods of determining these stresses have not developed substantially to keep pace with the increasing utilization of rock masses. Contributed by a group of leading experts, this book addresses new developments in numerical modeling and advanced measuring techniques. In-Situ Rock Stress: Measurement, Interpretation and Application reflect the development in this field, covering measuring techniques, interpretation methods, and application of the in-situ stress in engineering practice. Estimate of the in-situ rock stress state can be realized by direct or indirect methods. Although the indirect method has developed rapidly in recent years, the direct field measurement is still by far dominating. Great improvements have been achieved with the 'traditional' field tests by overcoring and hydraulic fracturing, whilst the recently developed methods become matured. In addition, ideas of new methods and new instruments will make the stress estimate easier, less expensive and more reliable.

This publication contains three special lectures, six keynote addresses and sixty-eight technical papers presented at the symposium. The wide variety of topics covered are grouped in the proceedings according to subject.

No other factor retards the progress of rock mechanics more than shortcomings in stress measurement. The papers presented at this symposium indicate progress in the development of techniques for measurement of stress and stress changes both on a field and point basis.