رساله دکتری با عنوان: Fracturing of layered reservoir rocks
دانشگاه : The University of Oklahoma
استاد راهنما: Dr. Ze’ev Reches
پژوهشگر: Seth Busetti
سال 2009
فرمت فایل: PDF و شامل 272 صفحه
چکیده:
The development of fractures in rock layers reflects a history of complex, non-linear, time-dependent mechanical processes. The processes strongly depend on the rock rheology, particularly the behavior during progressive deformation, layering effects such as the mechanical stratigraphy, and the local stress conditions. In the past, the complex mechanics associated with fracture initiation and propagation contributed to the application of simplified models based on linear rheology and using quasi-static solutions. While this approach is effective in solving infinitesimal strain problems, it provides no explanation for strain localization, damage accumulation and rock failure, and it oversimplifies fracture propagation. The objective of the present work is to contribute to the understanding of these processes.
The approach of this study is as follows. (Chapter 1) Theoretical advancements on fracturing and the concept of continuum damage mechanics are compared with rock mechanics experiments to understand progressive deformation, failure, and fracture propagation for rock. It is demonstrated that non-local (away from the crack-tip) yielding behavior must be considered to understand complex fracturing. (Chapter 2) A numerical rheology based on the elastic-plastic-damage properties of Berea sandstone is developed and calibrated to experimental rock mechanics data. A method for translating the stress-strain curve and acoustic emissions data into a material model included in the commercial finite element code Abaqus is presented. Two rock mechanics experiments are simulated in 3-D to test the rheology model. (Chapter 3) The rheology is implemented into finite element models based on classical hydraulic fracturing configurations. The explicit dynamic finite element method is used to simulate damage and transient propagation of a hydrofracture segment. It is shown that the complexity of fracturing depends on the local stress-strain response, which is controlled by the evolving damage pattern. The dynamical characteristics of arrest, rupture, branching, and segmentation of the fracture are described in terms of damage evolution. (Chapter 4) An analytical model for natural fracture reactivation is paired with the finite element simulations to understand the development of complex hydraulic fracture networks in the subsurface. The models' predictions are compared with data from hydraulically stimulated wells in the Barnett Shale. Recommendations are made for optimizing hydrofracture operations in wells for different states of stress (Chapter 5). The occurrence of zones of anomalously high fracture density is characterized in a carbonate sequence near Cedar Mountain Utah, and in Jackfork Group sandstone layers in Oklahoma and Arkansas. The results indicate that fracture density should be examined as a function of the evolving rock properties of the host layer in addition to the layer thickness.
The investigation contributes to understanding the process of damage and fracturing during the deformation of rock layers. The results describe the development of mechanical inhomogeneity in fractured rock layers and can be applied to explain the formation of complex hydraulic fractures in unconventional reservoirs.
مشاهده آنلاین و دریافت فایل نمونه:
https://drive.google.com/file/d/0B3BBM5yT_t4ZcmpQUjBiZmR3WW8
** توجه: خواهشمندیم در صورت هرگونه مشکل در روند خرید و دریافت فایل از طریق بخش پشتیبانی در سایت مشکل خود را گزارش دهید. **
پایان نامه کارشناسی ارشد با عنوان: Downstream hydraulic transients in combined free-surface, pressurized flow pipelines
دانشگاه : California State University, Long Beach
استاد راهنما: Antonella Sciortino
پژوهشگر: Nathan Faber
سال 2009
فرمت فایل: PDF و شامل 125 صفحه
چکیده:
The purpose of this research was to evaluate hydraulic transients in a combined free-surface, pressurized flow system with free-surface supercritical flow. This research focused on cases in which hydraulic transients are generated from the movement of a valve in the pressurized region of the system. A numerical model was developed to predict the hydraulic transients and the model was applied to simulate the hydraulic transients in a water transmission pipeline. The numerical model uses the Method of Characteristics for pressurized flow and supercritical, open-channel hydraulics to simulate the free-surface flow. Hydraulic transients in free-surface flow were not modeled as part of this research. Data analysis on hydraulic transient propagation and interaction with the pressurized/free-surface transition are presented.
مشاهده آنلاین و دریافت فایل نمونه:
https://drive.google.com/file/d/0B3BBM5yT_t4ZdWF5bFFfWlZzaTg
** توجه: خواهشمندیم در صورت هرگونه مشکل در روند خرید و دریافت فایل از طریق بخش پشتیبانی در سایت مشکل خود را گزارش دهید. **
رساله دکتری با عنوان: The lack of a clearly defined retention strategy and the impact of the retention of civil engineers
دانشگاه : Capella University
استاد راهنما: Tony Pizur
پژوهشگر: Aaron E. Forsythe
سال 2008
فرمت فایل: PDF و شامل 115 صفحه
چکیده:
Developing retention strategies for retaining professional employees has the potential of providing large cost savings to an organization associated with employee turnover. However, determining the needs of select groups of professional employees can be difficult to determine in today's markets. Through a quantitative fixed research design, this research used a survey to investigate the impact of a non-articulated retention strategy and the retention of civil engineering professionals. The responses from 361 participants indicated that there is statistical support that there is a root cause as to the low retention rate experienced by the organization. However, there does not appear to be a correlation between the root cause and the satisfaction of the civil engineers.
مشاهده آنلاین و دریافت فایل نمونه:
https://drive.google.com/file/d/0B3BBM5yT_t4ZUU1xS2UzMTNGSHc
** توجه: خواهشمندیم در صورت هرگونه مشکل در روند خرید و دریافت فایل از طریق بخش پشتیبانی در سایت مشکل خود را گزارش دهید. **
رساله دکتری با عنوان: Damage-free seismic-resistant self-centering concentrically-braced frames
دانشگاه : Lehigh University
استاد راهنما: Dr. James Ricles و Dr. Richard Sause
پژوهشگر: David Alan Roke
سال 2010
فرمت فایل: PDF و شامل 734 صفحه
چکیده:
A self-centering concentrically-braced frame (SC-CBF) system was developed to resist earthquake loading without structural damage or residual drift. An SC-CBF is a concentrically-braced frame with column base details that permit column uplift at a specified level of lateral force. This column uplift and the subsequent rocking of the SC-CBF soften the lateral force-lateral drift behavior of the system. Vertically-oriented post-tensioning bars provide restoring force and self-centering behavior that reduces the potential for residual drift. The SC-CBF members are designed to remain elastic under the design basis earthquake. Energy dissipation elements can be used to reduce the response of the SC-CBF system.
The scope of this study includes the development of a design procedure for SC-CBF systems, a parametric study of different SC-CBF configurations, analytical and experimental studies of a large-scale SC-CBF test structure, and evaluation of the performance of the SC-CBF test structure.
A performance-based design procedure and the associated design criteria were developed for SC-CBF systems. Nonlinear dynamic analyses of several 6-story prototype buildings with different SC-CBF configurations were performed to establish the lateral force behavior of the system and to study the influence of several design parameters on this behavior. An analytical model was developed to predict the earthquake response of SC-CBF systems. Hybrid simulations of the earthquake response of a large-scale SC-CBF test structure were performed to validate the analytical model. The seismic performance of the SC-CBF test structure was evaluated with respect to the performance-based design approach and criteria.
The results of this study indicate that the SC-CBF system performs very well under earthquake loading, and that the SC-CBF is a viable alternative to conventional CBF systems. The softening of the lateral force-lateral drift response of the system was due exclusively to the column uplift behavior; the beams, columns, and braces of the SC-CBF remained elastic. The performance of the SC-CBF test structure satisfied the performance-based design objectives and criteria.
The analytical and experimental results presented in this dissertation show that the performance of the SC-CBF systems can be designed to achieve reliable damage-free performance under the design basis earthquake. The probability of structural damage and residual drift under the design basis earthquake is low. The proposed performance-based design procedure and associated design criteria provide conservative estimates of design demands and provide excellent overall performance. The analytical model developed by this research provides accurate estimates of the earthquake response of SC-CBF systems.
مشاهده آنلاین و دریافت فایل نمونه:
https://drive.google.com/file/d/0B3BBM5yT_t4ZRUFlRGVVV19Xb1U
** توجه: خواهشمندیم در صورت هرگونه مشکل در روند خرید و دریافت فایل از طریق بخش پشتیبانی در سایت مشکل خود را گزارش دهید. **