Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3671. Adviser: Scott Olson. Includes bibliographical references (leaves 266-306) Available on microfilm from Pro Quest Information and Learning.

<p> Enhanced Geothermal Systems (EGS) have substantial potential as a domestic energy source and is well suited as an alternative to diversify the national energy portfolio due to its high levels of heat and recoverable energy. Hydraulic fracture stimulation of low permeability EGS reservoir rock is widely employed to develop this resource and is generally required to make unconventional resources an economically viable resource. Significant challenges for EGS technology include poor connectivity between injection and production wells during stimulation and difficulty predicting fracture growth (Tester, et al. 2006). This, coupled with notable advances in oil and gas recovery, has made hydraulic fracture mechanics the subject of considerable study. </p><p> Acoustic emissions, or microseisms, contribute greatly to these studies and have been employed on a wide range of topics in rock mechanic studies. At Colorado School of Mines, acoustic emission technology has been employed to monitor stimulation of cubic granite samples under heated and true triaxial stress environments to simulate deep reservoir conditions. Recorded AE activity was used to determine proper location of production well placement while additional analysis on the fracture process using characteristics such as wave amplitude and hit rates were used to identify stages of activity during fracture propagation. Study of the spatial and time dependence of the initiation and growth of rock fractures is critical to understanding the processes that govern fracture behavior and require details that are not accessible to alternative methods of analysis. Acoustic emissions can provide crucial information and represent an important part of rock mechanics studies.</p>

<p>This thesis is concerned with a design-oriented formulation of reinforced Segmental Retaining Wall (SRW) structures. The formulation follows the concept of the safety map used in slope stability analysis. It calculates the minimum tensile force requirement along each reinforcement layer by utilizing limit equilibrium method with log spiral surface. In the formulation, the force in the reinforcement at each location produces a limit equilibrium state. It considers the pullout capacity of each reinforcement layer. Consequently, the required distribution of tensile force along each layer is produced rendering a baseline solution for design. The calculated tensile force distribution considers the required force and pullout resistance of all other layers. Hence, it produces an optimized system where failure is equally likely to occur at any point within the reinforced soil mass. The developed framework enables one to decide the required strength of the connection between the reinforcement and the facing. Extensive parametric studies were carried out to evaluate the effect of the each component comprising the system. The parametric studies consider the wall geometry, the quality of backfill, the length and spacing of reinforcement, the effects of intermediate layers, the pullout resistance, the coverage ratio, the toe resistance, and the impact of seismic loading. Verification of the analytical framework was conducted through comparison with some records of full-scale and centrifuge experiments. Design implications are presented through some examples.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1183. Adviser: Timothy D. Stark. Includes bibliographical references (leaves 206-214) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4672. Adviser: Youssef M. A. Hashash. Includes supplementary digital materials. Includes bibliographical references (leaves 206-213) Available on microfilm from Pro Quest Information and Learning.