Claims
- 1. A method for forming a fragmented permeable mass of formation particles in an underground cavity in a subterranean formation, the underground cavity having top, bottom, and side boundaries of unfragmented formation, comprising the steps of:
- (a) excavating at least one limited void within the cavity boundaries in the subterranean formation while leaving at least one zone of unfragmented formation within the cavity boundaries adjacent such a limited void;
- (b) forming a plurality of spaced apart central blastholes in such a zone of unfragmented formation remote from the cavity side boundaries;
- (c) forming a plurality of spaced apart outer blastholes in the zone of unfragmented formation surrounding the central blastholes and adjacent the cavity side boundaries, the distance between adjacent outer blastholes being less than the distance between adjacent central blastholes;
- (d) loading explosive into the central blastholes for forming a central explosive charge in each such central blasthole;
- (e) loading explosive into the outer blastholes for forming an outer explosive charge in each such outer blasthole, such an outer explosive charge substantially filling the entire cross-sectional area of such an outer blasthole, the energy per unit length of such an outer explosive charge being less than the energy per unit length of such a central explosive charge; and
- (f) detonating the central and outer explosive charges for explosively expanding the zone of unfragmented formation toward the limited void for forming the fragmented permeable mass of formation particles in the underground cavity.
- 2. The method according to claim 1 wherein the actual depth of burial of each such central explosive charge is about equal to the actual depth of burial of each such outer explosive charge.
- 3. The method according to claim 1 wherein the distance between adjacent outer blastholes is at least about one-half the distance between adjacent central blastholes.
- 4. The method according to claim 1 wherein the ratio of the distance between adjacent outer blastholes to the amount of explosive in each outer blasthole is about equal to the ratio of the distance between adjacent central blastholes to the amount of explosive in each central blasthole.
- 5. The method according to claim 1 wherein the column length of each such outer explosive charge is about equal to the column length of each such central explosive charge.
- 6. The method according to claim 1 wherein such a zone of unfragmented formation comprises a free face adjacent the limited void and the central and outer blastholes are substantially perpendicular to the free face.
- 7. The method according to claim 1 wherein such a limited void extends generally horizontally in the subterranean formation, such a zone of unfragmented formation comprises a substantially horizontally extending free face adjacent the void, and the central and outer blastholes are substantially perpendicular to the free face.
- 8. The method according to claim 1 wherein the central and outer explosive charges are detonated in a single round.
- 9. The method according to claim 1 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the time delay between separate detonations in the sequence is sufficiently short so that proper interaction is achieved between all of the charges.
- 10. The method according to claim 1 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is less than about 3 milliseconds per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 11. The method according to claim 1 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is about 1 millisecond per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 12. A method for forming a fragmented permeable means of formation particles in an underground cavity in a subterranean formation, the underground cavity having top, bottom, and side boundaries of unfragmented formation, comprising the steps of:
- (a) excavating at least one limited void within the cavity boundaries in the subterranean formation while leaving at least one zone of unfragmented formation within the cavity boundaries adjacent such a limited void;
- (b) forming a plurality of spaced apart central blastholes in such a zone of unfragmented formation;
- (c) forming a plurality of spaced apart outer blastholes in the zone of unfragmented formation surrounding the central blastholes and adjacent such a retort side boundary, the distance between at least a first portion of adjacent outer blastholes being less than the distance between adjacent central blastholes, wherein the first portion of adjacent outer blastholes is nearer to objects sensitive to damage by seismic shock than the remainder of the outer blastholes;
- (d) loading explosive into the central blastholes for forming a central explosive charge in each central blasthole;
- (e) loading explosive into the outer blastholes for forming an explosive charge in each outer blasthole, such an outer explosive charge substantially filling the entire cross-sectional area of such an outer blasthole, the actual depth of burial of each such outer explosive charge being about equal to the actual depth of burial of each such central explosive charge while the energy per unit length of such an outer explosive charge in the first portion of adjacent outer blastholes is less than the energy per unit length of such a central explosive charge; and
- (f) detonating the central and outer explosive charges for explosively expanding the formation toward the limited void for forming the fragmented permeable mass of formation particles in the underground cavity.
- 13. The method according to claim 12 wherein such a zone of unfragmented formation comprises a free face adjacent the limited void and the central and outer blastholes are generally perpendicular to the free face.
- 14. The method according to claim 13 comprising detonating the central and outer explosive charges in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is less than about 3 milliseconds per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 15. A method for forming a fragmented permeable mass of formation particles in an underground cavity in a subterranean formation containing oil shale, the underground cavity having top, bottom, and side boundaries of unfragmented formation comprising the steps of:
- (a) excavating at least one void within the cavity boundaries in the subterranean formation, while leaving at least one zone of unfragmented formation within the cavity boundaries adjacent such a void;
- (b) forming a plurality of spaced apart central blastholes in such a zone of unfragmented formation remote from the cavity side boundaries;
- (c) forming a plurality of spaced apart outer blastholes in the zone of unfragmented formation surrounding the central blastholes and adjacent the cavity side boundaries, the distance between adjacent outer blastholes being less than the distance between adjacent central blastholes;
- (d) loading explosive into the central blastholes for forming a central explosive charge in each such central blasthole;
- (e) loading explosive into the outer blastholes for forming an outer explosive charge in each such outer blasthole, such as outer explosive charge substantially filling the entire cross-sectional area of such an outer blasthole, the actual depth of burial of each such outer explosive charge being about equal to the actual depth of burial of each such central explosive charge while the energy per unit length of such an outer explosive charge is less than the energy per unit length of such a central explosive charge; and
- (f) detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round comprising a sequence of separate detonations for explosively expanding the zone of unfragmented formation toward the void for forming the fragmented permeable mass of formation particles in the underground cavity, the time delay between detonations in the sequence being sufficiently short so that proper interaction is achieved between all of the charges.
- 16. The method according to claim 15 wherein the magnitude of such a time delay between detonations in the sequence is less than about 3 milliseconds per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 17. The method according to claim 16 wherein the magnitude of such a time delay between detonations is about 1 millisecond per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 18. A method for forming a fragmented permeable mass of formation particles in an in situ retort in a subterranean formation, the in situ retort having top, bottom, and side boundaries of unfragmented formation, comprising the steps of:
- (a) excavating at least one limited void within the retort boundaries in the subterranean formation, while leaving at least one zone of unfragmented formation within the retort boundaries adjacent such a limited void;
- (b) forming an array of blastholes in such a zone of unfragmented formation comprising at least one row of spaced apart central blastholes remote from the side boundaries of the retort;
- (c) forming a row of outer blastholes in such a zone of unfragmented formation adjacent at least one side boundary of the retort, the distance between adjacent outer blastholes being less than the distance between adjacent central blastholes;
- (d) loading explosive into the blastholes comprising such a row of central blastholes for forming a row of spaced apart central explosive charges in the zone of unfragmented formation;
- (e) loading explosive into the blastholes comprising such a row of outer blastholes adjacent such a side boundary of the retort for forming a row of spaced apart outer explosive charges in the zone of unfragmented formation, each outer explosive charge substantially filling the entire cross-sectional area of each outer blasthole, the scaled depth of burial of each such outer explosive charge being greater than the scaled depth of burial of each such central explosive charge; and
- (f) detonating the central and outer explosive charges for explosively expanding such a zone of unfragmented formation toward the limited void for forming a fragmented permeable mass of formation particles in the in situ retort.
- 19. The method according to claim 18 wherein the actual depth of burial of each outer explosive charge is about equal to the actual depth of burial of each central explosive charge.
- 20. The method according to claim 18 wherein the distance between adjacent outer blastholes is at least about one-half the distance between adjacent central blastholes.
- 21. The method according to claim 18 wherein the scaled depth of burial of such a row of outer explosive charges is about equal to the scaled depth of burial of such a row of central explosive charges.
- 22. The method according to claim 18 wherein such a limited void is a generally horizontally extending limited void and the central and outer explosive charges are substantially vertical columnar explosive charges.
- 23. The method according to claim 18 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the time delay between separate detonations in the sequence is sufficiently short so that proper interaction is achieved between all of the charges.
- 24. The method according to claim 18 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is less than about 3 milliseconds per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 25. The method according to claim 18 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is about 1 millisecond per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 26. A method for forming a fragmented permeable mass of formation particles in an in situ retort in a subterranean formation, the in situ retort having top, bottom, and side boundaries of unfragmented formation, comprising the steps of:
- (a) excavating at least one generally horizontally extending limited void within the retort boundaries in the subterranean formation, while leaving at least one zone of unfragmented formation within the retort boundaries having a substantially horizontally extending free face adjacent such a limited void;
- (b) forming an array of generally vertical blastholes in such a zone of unfragmented formation comprising at least one row of horizontally spaced apart central blastholes remote from the side boundaries of the retort;
- (c) forming a row of generally vertical outer blastholes in such a zone of unfragmented formation adjacent at least one side boundary of the retort, the distance between adjacent outer blastholes being less than the distance between adjacent central blastholes;
- (d) loading explosive into the blastholes comprising such a row of central blastholes for forming a row of horizontally spaced apart columnar central explosive charges in the zone of unfragmented formation, the columnar central charges being about perpendicular to the horizontally extending free face;
- (e) loading explosive into the blastholes comprising such a row of outer blastholes adjacent such a side boundary of the retort for forming a row of horizontally spaced apart columnar outer explosive charges in the zone of unfragmented formation, the columnar outer charges being about perpendicular to the horizontally extending free face, each outer explosive charge substantially filling the entire cross-sectional area of each outer blasthole, the scaled depth of burial of each such outer explosive charge being greater than the scaled depth of burial of each such central explosive charge; and
- (f) detonating the central and outer explosive charges for explosively expanding such a zone of unfragmented formation toward the limited void for forming a fragmented permeable mass of formation particles in the in situ retort.
- 27. The method according to claim 26 wherein the actual depth of burial of each outer explosive charge is about equal to the actual depth of burial of each central explosive charge.
- 28. The method according to claim 26 wherein the ratio of the distance between adjacent outer blastholes to the amount of explosive in each outer blasthole is about equal to the ratio of the distance between adjacent central blastholes to the amount of explosive in each central blasthole.
- 29. The method according to claim 26 wherein the ratio of the total amount of explosive in such a row of central explosive charges to the length of the row of central explosive charges is about equal to a ratio of the total amount of explosive in such a row of outer explosive charges to the length of the row of outer explosive charges.
- 30. The method according to claim 26 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the time delay between separate detonations in the sequence is sufficiently short so that proper interaction is achieved between all of the charges.
- 31. The method according to claim 26 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is less than about 3 milliseconds per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 32. The method according to claim 26 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is about 1 millisecond per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 33. A method for forming a fragmented permeable mass of formation particles in an in situ oil shale retort in a subterranean formation containing oil shale, the in situ oil shale retort having top, bottom, and side boundaries of unfragmented formation, comprising the steps of:
- (a) excavating at least one generally horizontally extending limited void within the retort boundaries in the subterranean formation, while leaving zones of unfragmented formation above and below such a limited void;
- (b) forming a plurality of spaced apart substantially vertical central blastholes in such a zone of unfragmented formation remote from the side boundaries of the retort;
- (c) forming a plurality of spaced apart substantially vertical outer blastholes in such a zone of unfragmented formation adjacent the side boundaries of the retort, the spacing distance between at least a first portion of such outer blastholes being less than the spacing distance between the central blastholes, wherein the distance from an outer blasthole comprising the first portion of outer blastholes to objects sensitive to damage by seismic shock is less than the distance from remaining outer blastholes to such objects;
- (d) loading explosive into the central blastholes for forming a central explosive charge in each central blasthole;
- (e) loading explosive into the outer blastholes for forming an outer explosive charge in each outer blasthole, such an outer explosive charge substantially filling the entire cross-sectional area of such an outer blasthole, the scaled depth of burial of each outer explosive charge in each outer blasthole of the first portion of outer blastholes being greater than the scaled depth of burial of such a central explosive charge; and
- (f) detonating the central and outer explosive charges for explosively expanding such a zone of unfragmented formation toward the limited void for forming a fragmented permeable mass of formation particles in the in situ oil shale retort.
- 34. The method according to claim 33 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is less than about 3 milliseconds per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 35. The method according to claim 33 wherein the actual depth of burial of each of the outer explosive charges is about the same as the actual depth of burial of each of the central explosive charges.
- 36. The method according to claim 33 wherein the spacing distance between the blastholes comprising the first portion of outer blastholes is at least about one-half the spacing distance between the central blastholes.
- 37. A method for forming a fragmented permeable mass of formation particles in an in situ oil shale retort in a subterranean formation containing oil shale, the in situ oil shale retort having top, bottom, and side boundaries of unfragmented formation, comprising the steps of:
- (a) excavating at least one limited void within the retort boundaries in the subterranean formation, while leaving at least one zone of unfragmented formation within the retort boundaries adjacent such a limited void;
- (b) forming an array of blastholes in such a zone of unfragmented formation comprising at least one row of spaced apart central blastholes remote from the side boundaries of the retort;
- (c) forming a plurality of spaced apart outer blastholes in such a zone of unfragmented formation adjacent the side boundaries of the retort, the distance between adjacent first outer blastholes being less than the distance between adjacent central blastholes, wherein the distance from such a first outer blasthole to objects sensitive to damage by seismic shock is less than the distance from remaining outer blastholes to such objects;
- (d) loading explosive into the central blastholes for forming a central explosive charge in each central blasthole;
- (e) loading explosive into the outer blastholes for forming an outer explosive charge in each outer blasthole, such as outer explosive charge substantially filling the entire cross-sectional area of such an outer blasthole, the actual depth of burial of each such outer explosive charge being about equal to the actual depth of burial of each such central explosive charge while the energy per unit length of the outer explosive charge formed in a first outer blasthole is less than the energy per unit length of such a central explosive charge; and
- (f) detonating the central and outer explosive charges for explosively expanding the zone of unfragmented formation toward the limited void for forming a fragmented permeable mass of formation particles in the in situ oil shale retort.
- 38. The method according to claim 37 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the time delay between separate detonations in the sequence is sufficiently short so that proper interaction is achieved between all of the charges.
- 39. The method according to claim 37 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is less than about 3 milliseconds per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 40. The method according to claim 37 wherein the distance between adjacent first outer blastholes is at least about one-half the distance between adjacent central blastholes.
- 41. A method for forming a fragmented permeable mass of formation particles in an in situ oil shale retort in a subterranean formation containing oil shale, the in situ oil shale retort having top, bottom, and side boundaries of unfragmented formation, comprising the steps of:
- (a) excavating at least one limited void within the retort boundaries in the subterranean formation, leaving at least one zone of unfragmented formation within the retort boundaries adjacent such a limited void;
- (b) forming an array of blastholes in such a zone of unfragmented formation comprising at least one row of spaced apart central blastholes remote from the side boundaries of the retort;
- (c) forming a row of outer blastholes in such a zone of unfragmented formation adjacent at least one side boundary of the retort, the distance between adjacent outer blastholes being less than the distance between adjacent central blastholes;
- (d) loading explosive into the blastholes comprising such a row of central blastholes for forming a row of spaced apart central explosive charges in the zone of unfragmented formation;
- (e) loading explosive into the blastholes comprising such a row of outer blastholes adjacent such a side boundary of the retort for forming a row of spaced apart outer explosive charges in the zone of unfragmented formation, each outer explosive charge substantially filling the entire cross-sectional area of each outer blasthole, the actual depth of burial of each such outer explosive charge being about equal to the actual depth of burial of each such central explosive charge while the energy per unit length of each such outer explosive charge is less than the energy per unit length of each such central explosive charge; and
- (f) detonating the central and outer explosive charges for explosively expanding such a zone of unfragmented formation toward the limited void for forming a fragmented permeable mass of formation particles in the in situ oil shale retort.
- 42. The method according to claim 41 wherein the distance between adjacent outer blastholes is at least about one-half the distance between adjacent central blastholes.
- 43. The method according to claim 41 wherein a row of outer blastholes is formed adjacent each side boundary of the retort.
- 44. The method according to claim 41 wherein the scaled depth of burial of such a row of outer explosive charges is about equal to the scaled depth of burial of such a row of central explosive charges.
- 45. The method according to claim 41 wherein the ratio of the distance between adjacent outer blastholes to the amount of explosive in each outer blasthole is about equal to the ratio of the distance between adjacent central blastholes to the amount of explosive in each central blasthole.
- 46. The method according to claim 41 wherein the ratio of the total amount of explosive in such a row of central explosive charges to the length of the row of central explosive charges is about equal to the ratio of the total amount of explosive in such a row of outer explosive charges to the length of the row of outer explosive charges.
- 47. The method according to claim 41 wherein the ratio of explosive energy per unit length of an outer charge to the distance between adjacent outer blastholes is about equal to the ratio of explosive energy per unit length of a central explosive charge to the distance between adjacent central blastholes.
- 48. The method according to claim 41 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the time delay between separate detonations in the sequence is sufficiently short so that proper interaction is achieved between all of the charges.
- 49. The method according to claim 41 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is less than about 3 milliseconds per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 50. The method according to claim 41 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is about 1 millisecond per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 51. A method for forming a fragmented permeable mass of formation particles in an in situ oil shale retort in a retort site in a subterranean formation containing oil shale, comprising the steps of:
- (a) excavating at least one limited void in the subterranean formation within the retort site, leaving at least one zone of unfragmented formation adjacent such a limited void;
- (b) forming an array of spaced apart central blastholes in such a zone of unfragmented formation;
- (c) forming a band of spaced apart outer blastholes in such a zone of unfragmented formation surrounding the array of central blastholes, the spacing distance between a plurality of first outer blastholes being less than the spacing distance between such central blastholes, such a first outer blasthole being smaller in diameter than such a central blasthole, wherein the distance from such a first outer blasthole to objects sensitive to damage by seismic shock is less than the distance from remaining outer explosive charges to such objects;
- (d) loading explosive into the central blastholes for forming a central explosive charge in each central blasthole;
- (e) loading explosive into the outer blastholes for forming an outer explosive charge in each outer blasthole, such an outer explosive charge in each first outer blasthole substantially filling the entire cross-sectional area of such a first outer blasthole, the actual depth of burial of each such outer explosive charge being about equal to the actual depth of burial of each such central explosive charge; and
- (f) detonating the central and outer explosive charges for explosively expanding such a zone of unfragmented formation toward the limited void for forming a fragmented permeable mass of formation particles in the in situ oil shale retort.
- 52. The method according to claim 51 wherein the spacing distance between the plurality of first outer blastholes is at least about one-half the spacing distance between the central blastholes.
- 53. The method according to claim 51 wherein the ratio of the spacing distance between the first outer blastholes to the amount of explosive in each first outer blasthole is about equal to the ratio of the spacing distance between the central blastholes to the amount of explosive in each central blasthole.
- 54. The method according to claim 51 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the time delay between separate detonations in the sequence is sufficiently short so that proper interaction is achieved between all of the charges.
- 55. The method according to claim 51 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is less than about 3 milliseconds per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 56. The method according to claim 51 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is about 1 millisecond per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 57. A method for forming a fragmented permeable mass of formation particles in an in situ oil shale retort in a subterranean formation containing oil shale, the in situ oil shale retort having top, bottom, and side boundaries of unfragmented formation comprising the steps of:
- (a) excavating at least one limited void within the retort boundaries in the subterranean formation, leaving at least one zone of unfragmented formation within the retort boundaries adjacent such a limited void;
- (b) forming an array of blastholes in such a zone of unfragmented formation comprising at least one row of spaced apart central blastholes remote from the side boundaries of the retort;
- (c) forming a row of outer blastholes in such a zone of unfragmented formation adjacent at least one side boundary of the retort, the distance between adjacent outer blastholes being less than the distance between adjacent central blastholes, wherein such outer blastholes are smaller in diameter than such central blastholes;
- (d) loading explosive into the blastholes comprising such a row of central blastholes for forming a row of spaced apart central explosive charges in the zone of unfragmented formation;
- (e) loading explosive into the blastholes comprising such a row of outer blastholes adjacent such a side boundary of the retort for forming a row of spaced apart outer explosive charges in the zone of unfragmented formation, each outer explosive charge substantially filling the entire cross-sectional area of such an outer blasthole, the actual depth of burial of each such outer explosive charge being about equal to the actual depth of burial of each such central explosive charge; and
- (f) detonating the central and outer explosive charges for explosively expanding such a zone of unfragmented formation toward the limited void for forming a fragmented permeable mass of formation particles in the in situ oil shale retort.
- 58. The method according to claim 57 wherein the distance between adjacent outer blastholes is at least about one-half the distance between adjacent central blastholes.
- 59. The method according to claim 57 wherein the scaled depth of burial of such a row of outer explosive charges is about equal to the scaled depth of burial of such a row of central explosive charges.
- 60. The method according to claim 57 wherein a row of outer explosive charges is formed adjacent each side boundary of the retort.
- 61. The method according to claim 57 wherein the ratio of the distance between adjacent outer blastholes to the amount of explosive in each outer blasthole is about equal to the ratio of the distance between adjacent central blastholes to the amount of explosive in each central blasthole.
- 62. The method according to claim 57 wherein the ratio of the total amount of explosive in such a row of central explosive charges to the length of the row of central explosive charges is about equal to the ratio of the total amount of explosive in such a row of outer explosive charges to the length of the row of outer explosive charges.
- 63. The method according to claim 57 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the time delay between separate detonations in the sequence is sufficiently short so that proper interaction is achieved between all of the charges.
- 64. The method according to claim 57 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is less than about 3 milliseconds per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
- 65. The method according to claim 57 comprising detonating the central and outer explosive charges in such a zone of unfragmented formation in a single round of sequential detonations wherein the length of the time delay between separate detonations in the sequence is about 1 millisecond per foot of spacing between an explosive charge in one delay and an adjacent explosive charge in the next delay in the sequence.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of application Ser. No. 183,144 filed Sept. 2, 1980, now abandoned, which is incorporated herein by this reference.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
4333684 |
Ricketts et al. |
Jun 1982 |
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Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
183144 |
Sep 1980 |
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