No description available.

This thesis details research conducted towards investigating the state of stress around inclined boreholes with the ultimate aim of predicting borehole stability and providing realistic estimates of closure stress. Chapter 1 discusses the factors affecting the stability of boreholes and reviews previous research conducted into borehole failure. The mechanics of hydraulic fracturing are reviewed as are methods of predicting fracture gradients. The manner in which closure stress is estimated is also critically reviewed. Chapter 2 describes an initial investigation into the stresses around inclined boreholes using the photoelastic technique of Stress Freezing. Chapter 3 details the laboratory determination of rock properties required for the borehole stability work detailed in Chapter 4. The applicability of the Brinell Hardness test to rock is also examined. Chapter 4 presents a detailed analysis of borehole stability. Failure criteria are developed and applied to estimate the mud weight required to maintain the hole in an elastic condition. To investigate the post-failure stability, existing 'yield zone' equations are modified to allow the effect of rock strength, oil flow rate, in-situ stress and hole angle to be examined. Chapter 5 describes the design and in-house manufacture of the specialised equipment required to measure fracture conductivity in the laboratory, the development of experimental procedures, the various test results and the conclusions drawn from them. Finally, the direct effect of a yield zone on the estimation of closure stress and on proppant selection is examined Chapter 6 summarises the conclusions that may be drawn from the work detailed in this thesis. The chapter also describes possible fields of future research which have been stimulated by the work presented. Two appendices are included, one providing a data-base of proppant properties, the other detailing the results of the application of the data-base to formation samples.

No description available.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1986. / Typescript (photocopy). Includes bibliographical references (leaves 67-76). Also issued in print.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1986. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 67-76).

No description available.

This thesis is a theoretical investigation into the thermal and structural response of large reflector support trusses subject to the space environment. A review of the elements necessary in a successful spacecraft design is included. The determination of the temperature distributions within large orbiting tetrahedral trusses is described. The thermal environment is shown to be an important factor'' in determining the performance of spacecraft. High quality microwave performance of the communication system depends upon the magnitude of distortions within the reflector support truss, and the thermal expansion or contraction of members makes a significant contribution to this distortion. The possibility of flexural vibration of individual members of the truss arising during entry into, or exit from, the earth's shadow is considered. Individual slender members and the radio frequency reflecting mesh cast shadows within the truss. A method for calculating the duration and position of such shadowing events is discussed. The effect that shadows have upon shadowee temperatures is determined using computer programs written by the author. Situations in which temperature gradients between the truss faces exist are highlighted. Such gradients produce bending deflections of the truss. Classical theories are developed to predict the magnitude of thermally induced stresses in the adhesive layer of tubular lap joints having dissimilar adherends. Tubular joints which contain a transition layer are also examined. An appropriately chosen transition layer will reduce the adhesive shear stresses by a substantial amount. Finally, the development of thermally induced stresses and damage mechanisms in laminated composite tubes is discussed. The designer must be aware of the amount of damage that spacecraft materials will experience during the long life missions envisaged for the near future.

The dissipation and spread of stresses in a granular material due to an applied disturbance is investigated. A single impulse was applied to a granular material to help understand its behaviour when disturbed by an oscillating vertical force. Measurements were made of the effect of the impulse at the surface of the beds of sand of various heights. The spread of the disturbance in a direction normal to that of application was measured by a radial traverse of the surface of each bed, The behaviour of a granular material when acted upon by a force is comprehensively discussed in the literature survey. The effect on the structure throughout the material of a disturbance applied at a distant point is then assessed.

No description available.

No description available.