Structural faults

The mosaic structure of a crystal is intimately connected with its mechanical strength. If we consider the lattice theory of a simple ionic crystal, such as sodium chloride, it is easy to calculate the stress necessary to rupture the crystal by separating it into two halves against the forces of interionic attraction. Such calculations lead to estimates of the tensile strength which are hundreds or thousands of times greater than those actually observed. If, however, the crystal possesses a mosaic structure the mechanism of fracture will be different. The two halves of the crystal will not now be separated simultaneously at every point instead there will be local stress concentrations at which the crystal will fail, the stress concentrations will then be transferred to other points and ultimately the crystal will break in two. The process may be likened to the tearing of a sheet of paper it is not easy to sever a piece of paper by means of a uniformly applied stress, but if a tear is started the stress is concentrated at the end of the tear, failure at that point takes place and the tear is rapidly propagated across the sheet. 

The mosaic structure of a crystal is one of its most profoundly structure-sensitive properties. As normally prepared, a crystal has a pronounced mosaic structure, but under conditions of more and more carefully controlled growth it is often possible to obtain crystals in which the degree of mosaic character is progressively reduced. As this process proceeds the X-ray reflexions become sharper and the mechanical strength increases. Conversely, by mechanical or thermal shock, it is often possible to reduce the degree of perfection of a carefully grown crystal. 

The idea that a crystal possesses a mosaic structure was introduced soon after the discovery of X-ray diffraction. It is only in recent years, however, that the nature of the imperfections giving rise to this structure has become known, chiefly as a result of investigations into the mechanical properties of metal crystals. 

We have already remarked that single crystals of the true metals are 

In addition to the edge dislocation there is also another type, known as a screw dislocation, which plays an important part in the process of crystal growth. 

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For many reasons it may not be possible or desirable to drill a vertical well. There may be constraints because of the surface location. In the subsurface, multiple targets, the shape of the structure, faults, etc. may preclude a vertical well. Figure 3.14 shows some of the deviated we//trajectories freguently used in industry deviated with tangent to target, S-shaped and horizontal. 

Keywords reservoir structures, faults, folds, depositional environments, diagenesis, geological controls, porosity, permeability... 

Structural Imperfections. In many respects HREM has had a greater impact upon our knowledge of the nature of the atomic reorganization at crystalline imperfections than any other single technique. One of the very first contributions of HREM as a new analytical and structural tool was described in the paper by Iijimia (42) in 1971 on 2 10 29 v -ewe< down to its b - axis. Structural faults, arising from subtle fluctuations in composition, could be clearly seen in the block-structure (based on NbO octahedra) which is a feature of this ternary oxide system. More than a decade later similar materials are yielding to active scrutiny by HREM, and Horiuchi (43), for example, has shown how point defects may be directly viewed... 

To summarize, we note that isolated interfaces within or between solids are regarded as structural faults, but that, in view of both experimental and computational evidence, it is often convenient to regard some structures as made up of regular sequences of stacking faults . 

Giro et al. (1986) measured hole mobilities of PVK prepared with different catalysts. Samples prepared with different catalysts show essentially the same mobilities. The mobilities were thermally activated with activation energies that increase with decreasing field. It was speculated that the low mobilities, relative to trap-free values of 10-3 cm2/Vs reported by Reimer and Bhssler (1979) and Fujino et al. (1982,1982a, 1984), were due to impurities originating during the polymerization process and linked to the main polymer chain and structural faults. 

Fault seal probability analysis is a quantitative method that allows an assessment of the risk of a fault acting either as a barrier to hydrocarbon migration, or as a trapping element within a structure. Fault seal probability is a value ranging from one to zero where a value of one is the highest probability for sealing, and zero is the lowest. This value is derived from the equation that combines the main parameters involved in the formation of fault seal. These parameters, fault displacement, connectivity, and net to gross ratio, are related to the processes of cataclasis and cementation, juxtaposition, and shale smear. The parameters, their measurement and impact on fault seal, are discussed below. 

M. Krause, Ch. Maierhofer, and H. Wiggenhauser, Thickness measurement of concrete elements using radar and ultrasonic impulse echo techniques, in Proc. 6th International Conf. on Structural Faults and Repair, Engineering Technics Press, London, 1995, pp. 17-24. 

Harpur Hill RAF reserve depot, 38, 39,43, 45,47, 103 Evacuation of, 44 Structural faults, 40 Harris, Captain, 123 Harrogate, evacuation of Air Ministry to, 244 Hartham Park Quarry, 181, 207-208,211-212 Hartlebury storage depot, 212 Hasley and Avening quarries (Gloucestershire), 15 Haughton, Major, 194 Hawker Tempest, 204 Hawker 5ea Fmo" 204 Hawker Typhoon, 204 Hawthorn (Corsham), 2... 

There are, in addition, quite other types of crystal defect which are best distinguished by being described as structural faults these we shall discuss separately ( 9.36-9.45). 

A recent renascence of interest in intercalation of various moieties between individual sheets of layered silicates, particularly montmorillonite, has resulted in a large number of published papers on these materials. High-resolution electron-microscopic studies of structural faults in kaolinite, zussmanite, and stilp-nomelane, and y-resonance spectroscopy studies of thermally initiated structural changes of montmorillonite and hydromica, have been undertaken. The nature of the exchange acidity and the thermal stability of the surface —OH groups of, inter alia, montmorillonite, montronite, vermiculite, and kaolinite, have also been examined. 

Isothermal operation not achieved - failure of cooling system, may have caused a structural fault. 

P. B. Bamforth, Concrete classification for R. C. stmctures exposed to marine and other salt-laden environments , Proc. of Structural Faults and Repair - 93, Edinburgh,... 

B. Elsener, Condition evaluation of reinforced concrete bridges - The benefits of potential mapping , in Proc. Int. Conf Structural Faults e[ Repair, London, Vol. 1, 47,... 

Alldred, J.C. (1993). Quantifying the Losses in Cover-meter Accuracy Due to Congestion of Reinforcement. Proc. 5th Inti. Conf. on Structural Faults and Repair, 2 125-130. 

Broomfield, J.P., Rodriguez, J., Ortega, L.M. and Garcia, A.M. (1993). Corrosion rate measurement and life prediction for reinforced concrete structures . Froc. Structural Faults and Repair-93, University of Edinburgh, Scotland, 2 155-164. 

McCartei W.J. and Vennesland, O. (2004). Sensor systems for use in reinforced concrete structures . Construction and Building Materials, 18 351-358. Raupach, M. and SchiessI, P. (Feb, 1995). Monitoring System for the Penetration of Chlorides, Carhonation and the Corrosion Risk for the Reinforcement. Proceedings of the 6th International Conference on Structural Faults and Repair. 

Hutchinson, A.R. Proceedings of International Conference on Structural Faults and Repair - 87, (Ed. Forde, M.C.), London University, July 1987, p. 235. 

Eyre, J.R. and Domone, P.L.J. 2nd International Conference on Structural Faults and Repair, I.C.E., London University, Engineering Technics Press, 1985, p. 141. 

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