Zhou, Yaneng
(2013)
Numerical Modeling of Rock Drilling With Finite Elements.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Rock drilling is the process employed to retrieve both the conventional and the unconventional resources, such as gas and oil buried deep under the ground. This study attempts to improve the understanding of the interaction between the drilling bit and rock by investigating the mechanics involved. In terms of achieving such a goal, a numerical modeling, if successful, can provide insights that are not possible through either field tests or laboratory experiments.
When the cutting depth progresses from shallow to deep, there is a failure mode transition from ductile to brittle, and a critical depth that governs this transition. This study introduced Bažant’s simple size effect law into interpreting the transition process of rock cutting. By treating the cutting depth as a measure of size, the law was found applied well to rock cutting based upon the data available in the literature, and the Finite Element Method (FEM) modeling results. By introducing the concept of characteristic length, this study also reinterpreted the previous understanding of the critical depth in rock cutting, by introducing the concept of characteristic length, and obtained the influence of characteristic length on critical depth through numerical modeling.
The Mechanical Specific Energy (MSE) and the Rate of Penetration (ROP) are two key factors for evaluating the efficiency of a drilling process and together they form a good base for strategizing a desirable drilling operation. In the absence of cutter wear rate, a relationship between MSE and ROP for a rectangular cutter has previously been suggested. This study presented a simple model for a circular cutter that includes the wear progression, which could explain the laboratory result of cutting high strength rock under high pressure.
The operation of a drilling bit in the field is mainly achieved through circular cutting action. This study extended the previous efforts and modeled first the circular cutting of a single disc cutter. This effort then formed the basis of a full drilling bit modeling presented at the end.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
|
| Date: |
28 June 2013 |
| Date Type: |
Publication |
| Defense Date: |
21 March 2013 |
| Approval Date: |
28 June 2013 |
| Submission Date: |
25 March 2013 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
171 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Civil and Environmental Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Rock cutting, Numerical modeling, Finite Element Method, Size effect, Ductile brittle transition |
| Additional Information: |
This version is updated based on reviewer's comments. |
| Date Deposited: |
28 Jun 2013 19:34 |
| Last Modified: |
15 Nov 2016 14:10 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/17904 |
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