Chapter13_Solutions.pdf

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C H A P T E R

13

BL STING ROCK

SOLUTIONS

13.1 According to the OSHA standard, what is the no smoking and no open flame zonefor an explosives and detonator storage magazine?

According to the OSHA standard 1926.904, smoking and open flames shall not

be permitted within 50 feetof an explosives and detonator storage magazine.

13.2 The detonation velocity of ANFO place in a 3-in. diameter column or a 9-in.diameter column is roughly the same. Is this a true statement? What is theexpected detonation velocity of poured ANFO in a 3-in. diameter column?

This is not a truestatement as column diameter effects detonation velocity ofANFO. 3-in. diameter 10,000 to 11,000 fps

13.3 To function properly, the stemming material should be angular and should havewhat average diameter in relation to the hole diameter?

To function properly, the stemming material should have an average diameter

0.05 times the diameter of the hole and it should be angular.

13.4 A contractor will use a packaged emulsion having a specific gravity of 1.2 andrelative bulk strength of 135, to open an excavation in granite rock, sp. Gr. 2.6.The drilling equipment available will drill a 4-in. blasthole. The explosive comepackaged in 3-in. diameter sticks. What is the recommended burden distancefor the first trial shot? Round the calculated burden distance to the nearest foot.(Burden 9 ft)

Use equ. 13.2:

B=0.67 3.5 362

135.

= 8.7 ft

Therefore recommend 9 ft burden distance.

PROPRIETARY MATERIAL. 2007 The McGraw-Hill Companies, Inc. All rights reserved. No partof this Manual may be displayed, reproduced or distributed in any form or by any means, without the priorwritten permission of the publisher, or used beyond the limited distribution to teachers and educators

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Chapter 13 BLASTING ROCK 13-2

PROPRIETARY MATERIAL

13.5 A contractor plans to use bulk ANFO, specific gravity 0.83, to open an excavationin sandstone. The drilling equipment available will drill a 3-in. blasthole. Whatis the recommended burden distance for the first trial shot? Round the calculated

burden distance to the nearest one-half foot.From Table 13-1, specific gravity of sandstone 2.0 to 2.8, use average 2.4 andequ. 13.1:

B=

+

1.5

2.4

0.8323.5 = 7.7 ft

Therefore, recommend a 7.5 ft burden distance.

. 2007 The McGraw-Hill Companies, Inc. All rights reserved. No part

13.6 A project in shale will have an average bench height of 28 ft. An emulsionrelative bulk strength 118, specific gravity 0.90, will be the explosive used on the

project. Dynamite sticks 8 in. long having a specific gravity of 1.3 and a diameterexactly equal to the De of the emulsion will be used as a detonator. Thecontractors equipment can easily drill 3-in.-diameter holes. It is assumed thatsingle rows of no more than ten holes will be detonated instantaneously. Theexcavation site has structures within 1,500 ft. The local regulatory agencyspecifies a Scaled distance factor of no less than 55. Develop a blast design for theproject. Round design dimensions to the nearest foot.

Specific gravity of shale 2.4 - 2.8, Table 13.1. Use 2.6.

Using equation 13.2 and an explosive diameter of 3 inches.

B= 0.67 3 32.6118 8.4

Evaluate stiffness ratio: L/B =8

283.5 Table 13.3: Good

Use 8 ft for burden distance in order to have good fragmentation.

Stemming depth, equation 13.4.

T = 0.7 8 = 5.6 ft

Use 6 ft for stemming.

Subdrilling depth, equation 13.5.

J = 0.3 8 = 2.4 ft

Use 2 ft for subdrilling.

Spacing, stiffness ratio greater than 1 but less than 4 and instantaneous initiation,equation 13.6.

of this Manual may be displayed, reproduced or distributed in any form or by any means, without the prior

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S =3

2(8)82 += 14.6 ft

14.6 15%: The range for S is 12.5 to 16.9 ft

As a first try use a 8

16 pattern.Powder column: 28 + 2 (subdrill) - 6 (stemming) = 24 ft

Table 13.4: emulsion, Sp. G. 0.9, column 3 inch; 3.75 lb/ft

dynamite, Sp. G. 1.3, column 3 inch; 5.42 lb/ft

(24 -0.67)ft 3.75 lb/ft = 87.5 lb per hole

0.67 ft 5.42 lb/ft = 3.6 lb per hole

Total 91.1 lb per hole

Total explosive per shot: 10 holes 91.1 lb per hole = 911 lb

Scaled distance factor, equation 13.12.

W

dDs W =

55

1,500

W = 744 lb91.1

744= 8.2 or 8 holes max instantaneously

Only 8 holescan be fired at one time (Ds= 55.6 > 55 ok).

13.7 The blasting in Problem 13.6 must be conducted so as to limit overbreakage.

Develop a presplitting blast plan.

Assume the same drill will be used, therefore, 3 inch holes.

Using equations 13.10 and 13.11:

dec = 35

280 44

2.. lb / ft

Sp = 10 3.5 = 35 inches

Bottom load should be: 3 0.44 = 1.32 lb

If 8 holes will be fired in the main shot will need to presplit a minimum distanceof 119 ft (17 ft spacing 7 spaces between 8 holes).

(119 ft 12 in/ft) 35 in = 41 presplit holes

Presplitting, no subdrilling: PC = 28

(28 ft 0.44 lb/ft) + 1.32 lb = 13.64 lb/hole

41 holes 13.64 lb/hole = 559 lb < 744 lb, vib. ok






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13.8 A project in limestone will have an average bench height of 20 ft. ANFO,specific gravity 0.90, will be the explosive used on the project. Dynamite,specific gravity 1.4 will be the primer explosives used. The dynamite comes in 8-

in.-long 1-in.-diameter sticks. The contractors equipment can easily drill 3-

in.-diameter holes. It is assumed that single rows of no more than ten holes willbe detonated instantaneously. The excavation site has structures within 900 ft.The holes will be lined. The thickness of the lining material is in. Calculate anappropriate burden distance for the blast design. To ease the fieldwork all designdimensions should be in integer numbers (ft).

Specific gravity limestone, 2.4 - 2.9, Table 13.1. Use average 2.65.

Using equation 13.1 and an explosives diameter of 3 inches (3-[2])

B =

5.165.2

90.023 = 6.54 ft

Evaluate stiffness ratio: L/B = 20/6.54 3.1 Good


Evaluate stiffness ratio: L/B = 20/6 3.3 Good

Use 6.0 ft for burden distance.

13.9 A project in dolomite will have an average bench height of 18 ft. An emulsionrelative bulk strength 105, specific gravity 0.8, will be the explosive used on theproject. Dynamite sticks 8 in. long having a specific gravity of 1.3 and a diameterexactly equal to the De of the emulsion will be used as a detonator. Thecontractors equipment can easily drill 3-in.-diameter holes. It is assumed thatsingle rows of no more than 10 holes will be detonated instantaneously. Theexcavation site has structures within 600 ft. The local regulatory agency specifiesa scaled distance factor of no less than 55. Develop a blast design for the project

using the maximum permissible integer spacing. (Burden 6 ft., stemming 4 ft.,

subdrilling 2 ft., 6 11 pattern, explosives 40.2 lb per hole, only 3 holes can befired at one time.)

Specific gravity of dolomite 2.8 - 2.9, Table 13-1. Use 2.9.

Using equation 13-2 and an explosive diameter of 3 inches.

B= 0 67 3 1052 9

6 73..

.


6 727

..= Table 13-3: Fair

Use 6 ft for burden distance in order to have a SR of 3.






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6 3= Stiffness ratio is good.

Stemming depth, equation 13-4.

T = 0.7 6 = 4.2 ft


Subdrilling depth, equation 13-5.

J = 0.3 6 = 1.8 ft


Spacing, stiffness ratio greater than 1 but less than 4 and instantaneous initiation,equation 13-6.

S f= +

=18 2 6

3 10

( )t

10 15%: The range for S is 8.5 to 11.5 ft

As a first try use a 6 11 pattern.

Powder column: 18 + 2 (subdrill) - 4.0 (stemming) = 16 ft

Table 13-4: emulsion, Sp. G. 0.8, column 3 inch; 2.45 lb/ft

dynamite, Sp. G. 1.3, column 3 inch; 3.98 lb/ft

(16 -0.67)ft 2.45 lb/ft = 37.6 lb per hole

0.67 ft 3.98 lb/ft = 2.7 lb per hole

Total 40.2 lb per hole

Total explosive per shot: 10 holes 40.21 lb per hole = 402 lb

Scaled distance factor, equation 13-12.

D d

W Ws =

60055=

W = 119.0 lb119 0

40 230

.

..= holes

Only 3 holes (Ds= 54.6 > 55 ok) can be fired at one time.






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13.10 A project in sandstone, having a specific gravity of 2.0, will have an averagebench height of 23 ft. An emulsion relative bulk strength 105, specific gravity0.8, will be the explosive used on the project. Dynamite sticks 1 ft long having aspecific gravity of 1.3 and a diameter exactly equal to the Deof the emulsion willbe used as a detonator. The contractors equipment can easily drill 4-in.-diameter

holes. It is assumed that single rows of no more than 30 holes will be detonatedinstantaneously. The closest structures to the excavation site are one-half mileaway. The local regulatory agency specifies a scaled distance factor of no lessthan 60. Even though an emulsion is being used because of expected wetconditions the holes will be lined. The thickness of the lining material is in.Develop the blast design spacing, subdrilling and stemming dimensions for theproject. How many holes can be fired instantaneously? The superintendent hastold you that good fragmentation will be acceptable.

Specific gravity sandstone, given 2.0


Burden = 0.67 3.5 302

105

.= 8.8 ft

Evaluate stiffness ratio: L/B = 23/8.8 2.6

Table 13.3: fair

Must reduce hole size:

Try drilling 3.5-inch holes. Therefore, 3 in. explosive diameter

Burden = .067

3.03

02

105

. = 7.5 ft

Evaluate stiffness ratio: L/B = 23/7.5 3.1 Good



T = 0.7 7.5= 5.3 ft



J = 0.3

7.5 = 2.3 ftUse 2 ft for subdrilling.

Spacing, stiffness ratio greater than 1 but less than 4 and instantaneousinitiation, equation 13.6.

S23 2(7.5 )

312.7 ft=

+






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As a first try use a 7.5 12 pattern. (7.511, 7.513, or 7.514 also acceptable)

Powder column: 23 + 2(subdrill) - 5(stemming) = 20 ft

Table 13-4: Emulsion Sp. G. 0.8, column 3 inch; 2.45 lb/ft

Dynamite Sp. G. 1.3, 3 inch sticks; 3.98 lb/ft

Emulsion (20 ft - 1ft dynamite)2.45 lb/ft = 46.6 lb per hole

Dynamite 1 ft 3.98 lb/ft = 4.0 lb per hole

Total explosive per hole 50.5 lb

Dd

Ws = Equ. 13.12

one-half mile = 5,280/2 = 2,640 ft

60 2640=W

W = 1936 lb

1936/50.5 = 38 Therefore all 30 holescan be fired instantaneously.

13.11 A project in limestone will have an average bench height of 18 ft. ANFO,specific gravity 0.84, will be the explosive used on the project. Dynamite, specificgravity 1.3 will be the primer explosives used. The dynamite sticks are 8-in. longby 1-in. in diameter. The contractors equipment can easily drill 3-in.-diameterholes. It is assumed that single rows of no more than 10 holes will be detonated

instantaneously. The excavation site has structures within 900 ft. The localregulatory agency specifies a scaled distance factor of no less than 60. The holeswill be lined. The thickness of the lining material is in. Develop a blast designfor the project.

Specific gravity limestone, 2.4 - 2.9, Table 13.1. Use average 2.65.


B =

+

51

652

8402.

.

.3 = 6.4 ft




Stemming depth, equation 13-4.

T = 0.7 6.0 = 4.2 ft







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J = 0.3 6.0 = 1.8 ft


Spacing, stiffness ratio greater than 1 but less than 4 and instantaneous initiation,equation 13.6.

S =3

)2(6.018+= 10.0 ft


As a first try use a 6 9 pattern. (610, or 611 also acceptable)

Powder column: 18 + 2(subdrill) - 4(stemming) = 16 ft

Table 13.4: ANFO Sp. G. 0.84, column 3 inch; 2.57 lb/ftDynamite Sp. G. 1.3, 1.75-inch sticks; 1.36 lb/ft

ANFO 15.33 ft 2.57 lb/ft = 39.5 lb per hole

Dynamite 0.67 ft 1.36 lb/ft = 0.9 lb per hole


Dd

Ws = Equ. 13.12 60

900=

W W = 225 lb

225/40.4 = 5.6 Therefore 5 holescan be fired instantaneously.

13.12 The blasting in Problem 13.11 must be conducted so as to limit overbreakage

develop a presplitting blast plan.

Assume the same drill will be used, therefore, 3 inch holes.

Using equations 13.10 and 13.11:

dec = 35

280 44

2.. lb / ft

Sp = 10 3.5 = 35 inches

Bottom load should be: 3 0.44 = 1.32 lb

If 5 holes will be fired in the main shot will need to presplit a minimum distanceof 36 ft (9 ft spacing 4 spaces between 5 holes).

(36 ft 12 in/ft) 35 in = 13 presplit holes

Presplitting, no subdrilling: PC = 18

(18 ft 0.44 lb/ft) + 1.32 lb = 9.24 lb/hole

13 holes 9.24 lb/hole = 120.1 lb < 225 lb, vib. ok






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13.13 A materials company is opening a new quarry in a limestone formation. Testshave shown that the specific gravity of this formation is 2.7. The initial miningplan envisions an average bench height of 24 ft. based on the loading and haulingequipment capabilities. Bulk ANFO, specific gravity 0.8, and a primer, specificgravity 1.5, will be the explosives used. The contractors equipment can drill 6-

in.-diameter holes. Delayed initiation will be utilized. Develop a blasting planfor a conservative cost estimate. (Burden 8 ft, stemming 6 ft, subdrilling 2 ft,spacing conservative 9 ft)

Specific gravity of the limestone is 2.7

Using equation 13.1 and an explosives diameter of 6 inches because of bulkANFO.

B =

+

51

72

802.

.

.6 = 12.6 ft

Evaluate stiffness ratio: L/B = 24 12.6 = 1.9 Table 13.3: Fair

This would most likely cause problems with excessive oversize material. Need toimprove the ratio.

Try drilling 4 inch blastholes and loading 4 inches.

B f=

+

=

2 08

2 715 4 0 8 4

.

.. . . t





T = 0.7 8.0= 5.6 ft



J = 0.3 8.0 = 2.4 ft


Spacing, stiffness ratio greater than 1 but less than 4 and delayed initiation,

equ.13.8.

S =8

)7(8.0+24= 10 ft

10 15%: The range for S is 8.5 to 11.5 ft

For a conservative cost estimate use an 8 9 pattern.






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13.14 An investigation of a highway project revealed a sandstone formation withsteeply dipping bedding into the face. Many weak joints were identified. Ananalysis of the plan and profile sheets, and the cross-sections showed that theaverage bench height will be about 15 ft. Bulk ANFO, specific gravity 0.8, andprimer, specific gravity 1.3 will be the explosives used on the project. The primer

comes in 8-in.-long 1-in.-diameter sticks. The contractors equipment caneasily drill 6-in.-diameter holes. It is assumed that delayed initiation will beutilized.

(a) Develop a blast design for the project.

Specific gravity sandstone, 2.0 2.8 use average 2.4

Using equation 13.1 and an explosives diameter of 2.5 inches

B=

+

=

2 08

2 415 2 5 54

.

.. . . ftTherefore 5 ft burden distance.


Burden corrected for rock deposition and structure. Table13.2

Bcorrected 0.95 1.3 5 = 6.2 ft



T = 0.7 6.0 = 4.2 ft



J = 0.3 6.0 = 1.8 ft


Spacing, stiffness ratio greater than 1 but less than 4 and instantaneousinitiation, equation 13.6.

S =3

)2(6.01 +5= 9.0 ft


As a first try use a 6

8 pattern. (6

8, 6

9 or 6

10 acceptable)Powder column: 15 + 2(subdrill) - 4(stemming) = 13 ft

Table 13.4: ANFO Sp. G. 0.8, column 2.5 inch; 1.70 lb/ft

Dynamite Sp. G. 1.3, 1.75 inch sticks; 1.36 lb/ft

ANFO 12.33 ft 1.70 lb/ft = 21.0 lb per holeDynamite 0.67 ft 1.36 lb/ft = 0.9 lb per hole






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(b) If the burden distance is held constant at 5 ft but the hole spacing is varied in1-ft increments across the range of Sdeveloped in part (a), what is the cost

per cubic of rock if the ANFO is $0.166 per lb, and dynamite $1.272 per lb?Try 6 8, 6 9, and 6 10, bench is 15 ft.

6 8 (48 ft sq 15 ft) 27 cu ft/cu yd = 26.7 cu yd



(10 ft - 8/12 ft) 1.09 lb/ft = 10.17 lb per hole

(8 in 12 in/ft) 1.36 lb/ft = 0.91 lb per hole

ANFO 21.0 lb $0.166 per lb = $3.480

Dynamite 0.9 lb $1.272 per lb = $1.153

Total $4.634 per hole

6 8 $4.634 26.7 cu yd = $0.174 per cu yd

6 9 $4.634 30.3 cu yd = $0.154 per cu yd

6 10 $4.634 33.3 cu yd = $0.139 per cu yd



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Chapter13_Solutions.pdf