Stability, Failure, and Measurements of Boreholes and Other Circular Openings (1993) / Chapter Skim
Currently Skimming:
1 Excavation, Maintenance, and Performance
1 Excavation, Maintenance, and Performance
Pages 5-12
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 5... ...
Once the circular opening reaches the fractured rock mass, collapse can occur due to severe weakening. In the more favorable cases, a pattern of steeply inclined fi actures can be observed along the was of the opening.
|
From page 6... ...
It is usually accepted that for hole sections further An three hole diameters from the face, this three-dimensiona1 supporting effect disappears. However, this rather short period of time can be sufficient to provide the wall with the temporary additional support necessary to compensate for the stress redistribution which occurs instantaneously.
|
From page 7... ...
A high-energy excavation process will not only confute the rock, but also damage the formation ;m~nediately around the opening, affecting its load-carr~ring capabilities. On the other Handel, the use of a very gentle breakage process in a highly stressed zone can be detrimental, as the intact rock has to support the full stress concentration.
|
From page 8... ...
· Delayed volume changes. Shale swelling, rock shrinkage due to dehydration, and time-dependent theological effects can cause substantial delayed deformations.
|
From page 9... ...
Decrease in Support Capacity Decreases in support capacity occur primarily in tunneling where the support might yield and lose its strength if excessive deformation of the hole had to be contained. Actions that could damage the efficiency of the mud cake can also decrease support capacity such as backflow during production or gas kick, mechanical action of the Ding assembly on the cake, and slug circulation.
|
From page 10... ...
Excessive creep associated with particular formations such as salt and potash is also known to be the origin of serious casing deformations. Insufficient Bonding Although an excavation can be completed without a major collapse or even without mayor problems during drilling, local instabilities can cause delayed problems; if good bonding is not achieved between the formation and the support.
|
From page 11... ...
The determination of such pertinent parameters such ~ the proper equation of state is a problem in itself as minor parametric variations lead to large consequences over long period of time.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.