Data processing: structural design – modeling – simulation – and em – Simulating nonelectrical device or system – Fluid
Reexamination Certificate
1999-09-08
2004-08-03
Jones, Hugh (Department: 2128)
Data processing: structural design, modeling, simulation, and em
Simulating nonelectrical device or system
Fluid
C703S002000, C703S005000, C175S002000, C102S311000, C102S312000
Reexamination Certificate
active
06772105
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains to bench blasting methods and, in particular, to a method of selecting the placement of boreholes along a drill line.
In modern bench blasting, vertical or near vertical holes are drilled adjacent to a rock face and are loaded with explosive charges that are then detonated. The detonation fractures the rock mass between the borehole and the rock face and displaces the resulting fractured rock. The resulting broken rock, known as “muck”, is removed and a new free rock face is thus exposed. If the muck contains a desired product, it can be gathered and processed. Otherwise, it may simply be removed from the blasting site to permit further blasting or other activities.
2. Related Art
U.S. Pat. No. 3,377,909 to Grant et al, issued Apr. 16, 1968, discloses the use of a “powder factor” (cubic yards of earth per pound of explosive) to characterize a borehole pattern in a coal field strip mine and discloses a “normal” spacing for ANFO (see col. 7, lines 70-71 and 6, lines 63-68).
U.S. Pat. No. 3,848,927 to Livingston, dated Nov. 19, 1974, discloses a trial and error method of determining the optimum and critical depths of a small charge, and teaches the scaling-up of this information for larger charges based on cube root scaling (see col. 7, lines 6-45). This patent suggests matching the charge to the desired size of debris.
U.S. Pat. No. 4,273,049 to Edwards et al, dated Jun. 16, 1981, suggests over-coming the dampening effect of water in a borehole by using water-resistant explosive in the water-containing portions of the borehole and conventional explosives above those portions.
U.S. Pat. No. 4,440,447 to Ricketts et al, dated Apr. 3, 1984, teaches that, in a borehole array for the formation of a retort in oil shale, outer boreholes can be closely spaced and made smaller in diameter to maintain the powder factor (see col. 8, lines 40-53), which is defined as the ratio of energy or explosive used per unit volume of formation explosively expanded in pounds ANFO equivalent per ton of oil shale formation expanded (see column 10, lines 13-17). No explanation of the term “ANFO equivalent” is given.
International Patent Application PCT/GB90/00567, which is incorporated herein by reference or background information, discloses a laser rangefinder device referred to by the trademark QUARRYMAN that can be used to survey a rock face and, when given a borehole pattern by the user, to calculate the burden associated with each borehole. This patent application also discloses a borehole analyzer referred to by the trademark BORETRAK that allows the user to determine the configuration of a borehole as actually drilled.
Prior art methods for assessing the rock hole burden associated with a given borehole or, alternatively, for predicting the optimum positions for boreholes along a rock face, made use only of gross approximations of the burdens associated with the boreholes. Typically, the volume of explosive material in the borehole is calculated and a known conversion factor corresponding to the powder factor disclosed in U.S. Pat. No. 3,377,909 (discussed above) is used to project a volume of rock to be associated with the explosive material in the borehole, i.e., the rock burden. The rock burden is then expressed as a roughly rectangular block, one dimension of which corresponds to the length of the column of explosive material in the borehole, another to the distance of the borehole to the rock face. The projected hole spacing along the drill line can then be derived as the third dimension of the rectangular block. This calculation method is highly inefficient because it does not take into account significant variations in the configuration of the rock face that can occur within the dimensions of the rectangular block associated with the borehole.
SUMMARY OF THE INVENTION
One broad aspect of the present invention pertains to a method for establishing a drill pattern for a plurality of boreholes of predetermined diameter for use with a specified explosive material along a drill line along a bench of rock having a known density and a rock face. The method comprises (a) defining a drill line having a start point and an end point; (b) determining a target rock burden B
T
for a hypothetical borehole having the predetermined diameter at the start point; (c) defining along the drill line a progression of successive layers of rock, each layer defining an incremental burden, and determining the cumulative burden B
cum
of the successive layers and revising B
T
with each successive layer until B
cum
accounts for one-half of B
T
; (d) setting and indicating a position for the borehole on the drill line in the most distant layer from the start point; (e) defining additional successive layers of rock until the total of the incremental burdens of the layers defined in steps (c) and (e) accounts for B
T
; (f) setting and indicating a location for a distant boundary of the rock burden for the borehole; and (g) using the distant boundary as the start point for an additional borehole and repeating steps (b), (c) (d), (e) and (f) for each additional borehole until a layer coincides with the end point.
In one example, such a method may comprise the foregoing steps (a) and (b) and then (c) defining along the drill line a progression of successive intermediate layers of rock each having a mass less than the target rock burden B
T
and being bounded by an intermediate boundary plane and a distant boundary plane and for each intermediate layer (i) calculating a revised B
T
based on a hypothetical borehole on the last defined boundary plane, and (ii) determining the cumulative burden B
cum
of the defined incremental intermediate layers until B
cum
accounts for one-half of B
T
and then setting and indicating the location of a borehole on the drill line in the last defined layer (referred to as the “central layer”); (d) defining along the drill line a progression of successive distant layers of rock, and accumulating the rock burdens of the layers until the total rock burden accumulated in steps (c) and (d) accounts for B
T
; (e) setting and indicating a location for a distant boundary of the rock burden for the borehole; and (f) using the distant boundary as a start point and returning to steps (b)-(e) until an incremental layer coincides with the end point.
Optionally, the position of the borehole may be set between the planar boundaries of the central layer by interpolation or on one of the boundaries.
Another aspect of this invention relates to a method for proposing a drill pattern comprising positions for boreholes of predetermined diameter for use with a specified explosive material along a drill line along a bench of rock having a known density and rock face. The method comprises (a) defining a drill line having a start point and an end point; (b) determining a target rock burden (B
T
) for a hypothetical borehole having a height corresponding to the start point; (c) defining along the drill line a progression of successive layers of rock each having a mass less than B
T
and each being bounded by planar cross sections of the bench and having an intermediate boundary plane and a distant boundary plane, determining the cumulative burden B
cum
of the defined layers, and calculating an average height of the layers with each successive layer; (d) using the average height to calculate a revised B
T
for the hypothetical borehole; and (e) repeating steps (c) and (d) until B
cum
accounts for B
T
and then indicating the location of a borehole on the drill line between the start point and the most distant layer, and using the distant boundary of the most distant layer as a start point and returning to step (b) until a layer coincides with the end point.
According to one aspect of the invention, calculating the average height of the incremental layers may comprise defining spaced parallel planes that define layer boundaries and taking the average height of the planes.
According to another aspect of the invention, the rock mass of a laye
Ferris Fred
Jones Hugh
Live Oak Ministries
Myers Kurt S.
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