Wells – Processes – With explosion or breaking container to implode
Reexamination Certificate
1999-07-23
2001-04-10
Schoeppel, Roger (Department: 3672)
Wells
Processes
With explosion or breaking container to implode
C299S013000, C299S022000, C102S304000, C102S313000, C102S322000, C102S333000
Reexamination Certificate
active
06213212
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
“Not Applicable”.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
“Not Applicable”.
BACKGROUND OF THE INVENTION
The present invention relates generally to a method of shattering earth formations by drilling boreholes in the formation and placing explosives therein which are detonated. More particularly, the invention relates to a method of plugging a borehole at any desired position in order to improve the performance of the explosives, and reduce the danger of fly rock and stemming ejection.
A conventional method of shattering earth formations in mining or excavation operations includes the steps of drilling a plurality of boreholes in the formation in a predetermined array, placing a predetermined amount of explosives in the boreholes, and detonating the explosives in a conventional sequence. Typically, the boreholes are not completely filled with explosives, but are plugged at the top by a stemming material such as crushed rock. In addition, the stemming at the tops of the boreholes may be spaced from the explosives by an air deck and/or other additional layers of air, explosives and stemming or plugging material.
Regardless of the number and arrangement of materials and decks in the boreholes, the upper layer of stemming is intended to plug the top of the borehole and confine the blast for a few extra milliseconds than would otherwise be the case in order to improve the cratering produced by the explosives and the fragmentation of material being shattered and to reduce dangerous fly rock and stemming ejection. As such, it is considered an important step in known processes to provide the stemming layer at the upper ends of the boreholes.
Although crushed rock is preferably used as the stemming material in mining and excavation operations, it is not always readily available, and must sometimes be shipped to the mining site for use. Because mining and site preparation is often conducted in urban locations, fly rock and stemming ejection can be dangerous. As such, there is a need for a stemming plug construction capable of use with readily available materials to prevent such dangerous conditions. Unfortunately, drill cuttings are much smaller than crushed rock, usually on the order of 6 mesh down to 200 mesh in size, and are easily blown from the boreholes upon detonation of the explosives. As such, very little confinement of the blast results, reducing the amount of cratering and fragmentation relative to that achieved when crushed rock is employed as the stemming material. The stemming plug in conjunction with crushed rock provides extra safety in confined areas where stemming ejection and fly rock can be dangerous.
BRIEF SUMMARY OF INVENTION
It is an object of the present invention to solve the technical problems left unaddressed by the prior art, and to provide a method of plugging boreholes in mining and excavation operations that employs readily available material without adversely affecting the amount of cratering and fragmentation and prevents dangerous conditions.
In accordance with these and other objects evident from the following description of a preferred embodiment of the invention, a method of plugging a borehole comprises the steps of placing a first layer of stemming in the borehole, placing a spherical body in the borehole on top of the stemming, and placing a second layer of stemming in the borehole over the body. The body includes a hard sphere and a diameter slightly smaller than the diameter of the borehole, and is preferably formed of a hard synthetic resin material such as ultra-high molecular weight polyethylene, or any material of similar minim hardness or a hard shell filled with a fluid, sand or other relatively hard material. The stemming preferably includes crushed rock but may include drill cuttings such as those produced during formation of the boreholes, ranging in size from about 6 mesh down to 200 mesh in size. However, gravel or other conventional stemming materials may also be employed in the method.
The borehole plug of the present invention preferably includes a first layer of stemming material adapted to be placed in the borehole, a second layer of stemming material adapted to be placed in the borehole above the first layer of stemming material, and a spherical body positioned between the first and second layers of stemming material, wherein the body is relatively hard and incompressible, and includes a diameter slightly smaller than that of the borehole in which the plug is to be used.
By providing a method and/or apparatus in accordance with the present invention, numerous advantages are realized. For example, by providing a method in which a pair of layers of stemming material are placed in a borehole with a relatively hard spherical body, a plug is defined in which the spherical body cooperates with the stemming material to prevent the stemming material from being ejected along the borehole during blasting. As such, the performance of the explosive material is comparable or better than with arrangements in which the stemming material is employed without the plug body.
REFERENCES:
patent: 4637312 (1987-01-01), Adams et al.
patent: 4796533 (1989-01-01), Yunan
“Rocklock”®, date unkown.
Jenkins Thomas S.
Jenkins, Jr. Sanford S.
Schoeppel Roger
Shook Hardy & Bacon L.L.P.
Stemlock, Incorporated
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