new prowall manual

ProWall

developed by Blast Dynamics, Inc.

ProWall - Operation Guide

ProWall v10.5 by Blast Dynamics, Inc. ©1/05

Introduction

The ProWall software is designed to assist with the development of blast designs that minimize slope damage. Blast plans can be developed, evaluated and compared to achieve optimum explosives and cost performance. The software can be used to:

• create a database of explosives commonly used

• easily develop relatively complex designs

• plot a cross sectional and plan view of the design

• perform a complete drilling, loading and blasting cost evaluation of the design

• store the design in a database for future reference

• compare plans in terms of design parameters, performance and cost

Installing the ProWall software

Follow the procedure below to install and use ProWall

1) Install Microsoft Excel v5.0 or greater on your computer

2) Create a folder (or directory) called ProWall on your hard drive

3) Copy the workbook ProWall from the CD provided to the ProWall folder. Remove the CD and store it in a safe place.

Using the ProWall software

1) Start ProWall by double clicking its icon. The initial worksheet that will open will be the Design sheet.

2) To make ProWall easy to use there are “buttons” that perform specialized tasks. The buttons on the Design sheet are shown below.


The function of each of these buttons will be covered in the description of each sheet.

Introduction

Using the ProWall software (cont.)

3) The ProWall worksheets will allow you to enter values only in cells that are outlined and have BLUE text. This will prevent you from changing a formula or label cell by mistake. If you enter a value into a protected cell and press enter the program will not accept the entry.

4) After you have entered your data, check the calculations by scrolling through the worksheet using the scroll bar. If any cell displays #DIV/0 or Error then

one or more of the variable cells may not have numerical data in them. Be sure not to enter text or blank spaces into cells that require number values. If any cell shows ###### the value in the cell is too long to display. This can usually be corrected by checking the variable cells for proper input or reducing the estimated volume or mass to be shot.

5) At the bottom of the screen there are tabs for the other worksheets.

You can activate the worksheet by pressing its tab. Each worksheet will be discussed in detail in the following sections.


Explosive Worksheet

Purpose:

The Explosive worksheet is a database that allows you to enter the characteristics of over 200 explosives. Once entered, this information can then be used by the Design worksheet. By entering explosives into the database you will save time and reduce entry mistakes when designing blasts.

Instructions:

Start the ProWall program and select the Explosive tab item from the bottom of the screen. The Explosive worksheet will be opened and the screen will look similar to the illustration shown here.

ProWall - Explosive DatabaseExplosive Database Enter the explosives data under the appropriate title.Explosive Dia. Den. Ener Velo. RBS to Cost Company CommentsName (in) g/cc cal/g ft/s ANFO $/lbNone

1" presplit 1 1.20 880 14,000 139% $2.0000 continuous presplit

1 1/4" presplit 1.25 1.20 880 14,000 139% $1.8000 continuous presplit



2" presplit 2 1.20 880 14,000 139% $1.6000 continuous presplit

ANFO 7.875 0.82 890 13,700 96% $0.1400

20/80 HANFO 1.10 840 15,500 122% $0.1500 20% Emulsion - 80% ANFO Blend



Emulsion 1.25 750 17,500 124% $0.1750 Straight Emulsion - Pumped

Low Density 0.60 890 10,000 71% $0.1400


Explosive Worksheet

Instructions (cont.):

All of the ProWall worksheets share a common user interface for ease of use. Included in the common features are “action” buttons and

unprotected data entry cells. The “action” buttons perform tasks automatically when pushed.

The Explosive worksheet includes the following “action” buttons:

Clear All – clears all of the explosive information from the database. When the button is pressed the following dialog box is displayed:

Press the Yes button to clear all explosive information

Imperial – changes the entry parameters from metric to imperial units. Note when the Imperial button is selected its label changes to Metric. To change the parameters from imperial back to metric press the Metric button.

Clear One – allows you to delete the parameters of just one explosive from the database. To remove the parameters select the name of the explosive that you wish to delete and then press the Clear One button.

All of the data entry cells in ProWall are outlined and have blue text.


Slope Calculations Worksheet

Purpose:

The Slope Calculations worksheet provides a simple way to determine catch bench widths and calculate inter ramp slope angles. A graphical representation of the design is produced by the worksheet.

Instructions:

Start the ProWall program and select the Slope Calculations tab item from the bottom of the screen. The Explosive worksheet will be opened and the screen will look similar to the illustration shown here.

The Slope Calculations worksheet includes the following “action” buttons:

Update From Design – updates the data entry fields with information from the design sheet and plots the current design


Goto Design – opens the Design worksheet

Plot Slope – refreshes the slope graphic with the current design

Print – prints the information displayed on the screen

Slope Calculations Worksheet

Instructions (cont.):

A Slope Calculations data entry box is displayed the left side of the screen.

Slope Calculations Enter 1 for Metric, 2 for Imperial Units 2

Operation: Modified or Trim BlastDesign: Average Conditions

Desired Bench Height: 40 ftModified Ritchie Criteria

Bench Height Multiplier: 0.2 ft typically .16 to .20Width Factor: 15 ft typically 14 to 15 ft

Minimum Bench Width: 23 ft

Desired Catch Bench Width: 23 ft

Desired Face Angle: 65 deg

Presplit Hole Angle

Face Angle

Hole Length

Toe Offset

Inter-Ramp Angle

25 65 44.1 18.6 43.8

0 90 40.0 0.0 60.15 85 40.2 3.5 56.510 80 40.6 7.1 53.115 75 41.4 10.7 49.920 70 42.6 14.6 46.8

25 65 44.1 18.6 43.830 60 46.2 23.1 41.035 55 48.8 28.0 38.1

The minimum catch bench width is calculated using the Modified Ritchie formula. In the example shown above the minimum allowable bench width is 23 ft for a 40 ft bench height. The Bench Height multiplier typically ranges from .16 to .20 depending on the structural conditions of the rockmass and the anticipated blast damage. Higher Bench Height multiplier values will increase the minimum allowable bench width. The width factor normally ranges between 14 and 15 ft depending on the required “carry” capacity of the bench.

Once the Minimum Bench Width has been calculated, enter the desired bench width and face angle in the appropriate fields. The table will then be updated to show calculated inter ramp angle for the given data as well as the resultant inter-ramp angle


for other bench face angles. In the example shown above the calculated inter-ramp angle is 43.8 degrees. If a bench face angle of 70 degrees can be achieved, the resultant inter-ramp angle would be 46.8 degrees.

Press the Plot Slope button to see a graphical representation of the current design.

Design Worksheet

Purpose:

The Design worksheet allows you to easily develop relatively complex wall control blast designs. Once the design is entered the worksheet calculates the presplit, energy and powder factors for each row. In addition the total required drill production is also calculated.

Start up:

Start the ProWall program and select the Design tab item from the bottom of the screen. The worksheet will be opened and the screen will look similar to the one shown here.

The Design worksheet includes the following buttons:

Clear All – clears all of the explosive information from the database

Goto Database – opens the blast design database

Imperial – changes the entry parameters from metric to imperial units. Note when the Imperial button is selected its label changes to Metric. To change the parameters from imperial back to metric press the Metric button.


Plot Design – plots and displays the current design.

Save – saves the design to the data base.

Print All – prints the design data, a plot of the design, the cost parameters and a timing design sheet.

Design Worksheet

Start up (cont.):

The Design worksheet is divided into four main sections; slope design, explosive loading, pattern design and summary data.

Each of these sections will be discussed in detail on the following pages.

To help with the learning process we will load a sample blast design into the Design worksheet. Press the Goto Database button. The screen should look similar to the one shown below.

Select the Sample Wall Design cell from the Operation column and press the Plot Design button. The program will load the Sample Wall Design into the Design worksheet and plot the design in the Design Plot worksheet. Your screen should resemble the illustration shown below:


Design Worksheet

Start up (cont.):

Press the Goto Design button to return to the Design worksheet. Your screen should now look like the one shown below:


ProWall - Design Data

Operation: Current Date: 10-May-05Location: Designed On: 9-May-05

Slope Design

Bench Height (ft): 40.0 Rock Density (g/cc): 2.60

Catch Bench Width (ft): 23.0 Rock Structure: blocky

Face Angle (deg): 65.0 Compressive Strength (psi): 12,000

Inter-Ramp Slope Angle (deg): 43.9 Water Conditions: dry

Blast Length (ft): 1,000 Face Height (ft): 40

Staggered Pattern (y or n): y Blast Adjacent To Catch Bench? (y or n) y

Explosive Loading Toe or Presplit Inner Outer Crest or ModifiedRow Buffer Row Buffer Row Prod. Row

Toe Charge Type: None None None None

Charge Diameter (in):

Density (g/cc):

Abs. Wt. Strength cal/g):

Detonation Velocity (ft/sec):Desired Bot. Charge (lb):

Charge Length (ft):

Column Charge Type: ANFO ANFO ANFO ANFO

Charge Diameter (in): 9.875 9.875 9.875 9.875

Density (g/cc): 0.82 0.82 0.82 0.82

Abs. Wt. Strength (cal/g): 890 890 890 890

Detonation Velocity (ft/sec): 13,700 13,700 13,700 13,700

Desired Col. Charge (lb): 680.0 750.0 750.0 750.0

Charge Length (ft): 25.0 27.5 27.5 27.5

Pattern Design Toe or Presplit Inner Outer Crest or Modified

Row Buffer Row Buffer Row Production Row

Blasthole Diameter (in): 9.875 9.875 9.875 9.875

TC Borehole Pressure (psi):

CC Borehole Pressure (psi): 260,101 260,101 260,101 260,101

Blasthole Angle (deg):

Drill Offset at Toe (ft):

Top Overbreak (ft): 24 Top Face Burden (ft): 5.0

Bottom Overbreak (ft): 5 Offset From Slope Bot. Face Burden (ft): 24.0Batter Angle (deg): 65 29.0 Face Angle (deg): 65

Burden (ft): 24 24 24 14.5Bench Top Width (ft): 101.0 s/b ratio s/b ratio s/b ratio

Bench Bottom Width (ft): 96.0 1.0 1.0 1.7

Spacing (ft): 24 24 24 24

Airdeck (ft):

Subdrill or Standoff (ft): 6 6 6

Stemming (ft): 15.0 18.5 18.5 18.5

Scaled Depth Of Burial: 1.45 1.74 1.74 1.74

Blasthole Length (ft): 40.0 46.0 46.0 46.0

Presplit Factor (lb/ft^2): 0.71 note:initial presplit factor should be around 0.1Powder Factor (lb/ton): 0.23 0.40 0.40 0.66

Energy Factor (kcal/ton): 92 162 162 268

Summary Data Total Mass Shot (tons): 327,725

Face Energy Ratio at Top 0.62 Required Drill Production (ft): 7,417

Face Energy Ratio at Bot. 1.08 Overall PF (lb/ton): 0.37

Overall Energy Factor (kcal/ton): 151

Post Blast Performance: typical modified production blast with free face

Modified or Trim BlastAverage Conditions

Design Worksheet

Design Parameters:

The Slope Design section of the Design worksheet is shown below:


Slope Design



Face Angle (deg): 65.0 Compressive Strength (psi): 12,000


Blast Length (ft): 1,000 Face Height (ft): 40

Staggered Pattern (y or n): y Blast Adjacent To Catch Bench? (y or n) y

The following graphic illustrates some of the entry data required.

batter orbench face angle

catch bench width

benchheight

desired bench face

crest

toe

Design Worksheet

Design Parameters (cont.):

The slope angle is calculated from the bench height, catch bench width and batter angle parameters. The information required by the rest of the Slope Design parameters is as follows:


Blast Length (ft) – enter the length of the wall to be shot (such as the perimeter of the pit) or simply the length of an individual blast. This number will be used to calculate the drilling, loading and explosive requirements of the design and the associated costs.

Staggered Pattern (y or n) – enter y if the drill pattern will be staggered and n if the pattern is not staggered. Note: staggered patterns are typically used.

Rock Density (g/cc) – enter the rock density in grams per cubic centimetre. This number is used to calculate the tonnes of material in the blast.

Rock Structure – enter fabric or structure of the rockmass (i.e. blocky, open joints, massive, etc.). This information is used to help define the zone that the blast will be used in. No actual calculations will be based on this data.

Compressive Strength (psi) –enter the rocks compressive strength in pounds per square inch. This information is used to help document the material that the blast will be used in. No actual calculations will be based on this data.

Design Worksheet



staggered pattern

square pattern

Water Conditions – enter the anticipated water conditions that the design will be used in. No calculations will be based on this data.

Face Height - enter the height of the final bench face. For example, if double benching is used the face height would be 80 ft.

Blast Adjacent To Catch Bench - enter y or n depending on if the design will be used directly above the catch bench. If double benching is used and the design is for the top flitch enter n.

The Explosives Loading section of the Design sheet is shown below:

Explosive Loading Toe or Presplit Inner Outer Crest or ModifiedRow Buffer Row Buffer Row Prod. Row


Charge Diameter (in):

Density (g/cc):

Abs. Wt. Strength cal/g):

Detonation Velocity (ft/sec):Desired Bot. Charge (lb):

Charge Length (ft):



Density (g/cc): 0.82 0.82 0.82 0.82

Abs. Wt. Strength (cal/g): 890 890 890 890

Detonation Velocity (ft/sec): 13,700 13,700 13,700 13,700

Desired Col. Charge (lb): 680.0 750.0 750.0 750.0

Charge Length (ft): 25.0 27.5 27.5 27.5

Note that the design sheet can accommodate up to four rows of blastholes. Each row can have a toe and a column charge. If only one charge is placed in the hole then that charge should be entered into the column charge section. Explosives that are in the explosive database can automatically be loaded into the design sheet by pressing the GET button.Be sure to enter the desired explosive charge diameter and weight so the sheet can calculate the charge length.

Design Worksheet


When continuous presplit explosives are used it is common practice to double over the charge in the bottom of the hole to help define the toe of the bench. The Toe Charge


Calculations data entry box calculates the effective weight and diameter of the doubled column charge.

Column Charge Type: 1 1/4" presplit

Charge Diameter (in): 1.25

Density (g/cc): 1.2

Abs. Wt. Strength (cal/g): 880

Detonation Velocity (ft/sec): 14,000

Desired Col. Charge (lb): 22.0

Charge Length (ft): 34.5

Length: 5.0

Weight: 6.6

Doubled Presplit Diameter: 1.8

Toe Charge Calculations

In the example shown above, a doubled 5 ft length of 1 ¼” continuous presplit explosive would weigh 6.6 lb and have a effective diameter of 1.8 inches. Those values should be entered as shown below along with the explosive data in the Toe Charge fields.

Toe Charge Type: 1" presplit

Charge Diameter (in): 1.8

Density (g/cc): 1.2

Abs. Wt. Strength cal/g): 880

Detonation Velocity (ft/sec): 14,000Desired Bot. Charge (lb): 6.6

Design Worksheet



The row designations are shown in the next illustration.

Note: the Parameters worksheet includes this same information.

All blast designs must have information entered into at least the toe and modified production rows. This allows the worksheet to calculate the back and the face of the blast. In other words, the worksheet can calculate designs for two three or four row blasts.

Design Worksheet


Slope Design Parameters

batter angle

slope angle

catch bench width

inne

r b

uffer

ro

w

oute

r b

uffer

ro

w

mod

ified

pr

oduc

tion

row

toe

or

pr

espl

it r

ow

benchheight


The Pattern Design section of the Design worksheet is shown below.

Pattern Design Toe or Presplit Inner Outer Crest or Modified


Blasthole Diameter (in): 9.875 9.875 9.875 9.875

TC Borehole Pressure (psi): 4,756

CC Borehole Pressure (psi): 1,843 260,101 260,101 260,101

Blasthole Angle (deg):

Drill Offset at Toe (ft):

Top Overbreak (ft): 24 Top Face Burden (ft): 5.0

Bottom Overbreak (ft): 5 Offset From Slope Bot. Face Burden (ft): 24.0Batter Angle (deg): 65 29.0 Face Angle (deg): 65

Burden (ft): 24 24 24 14.5Bench Top Width (ft): 101.0 s/b ratio s/b ratio s/b ratio

Bench Bottom Width (ft): 96.0 1.0 1.0 1.7

Spacing (ft): 24 24 24 24

Airdeck (ft):

Subdrill or Standoff (ft): 6 6 6

Stemming (ft): 0.6 18.5 18.5 18.5

Scaled Depth Of Burial: 0.39 1.74 1.74 1.74

Blasthole Length (ft): 40.0 46.0 46.0 46.0

Presplit Factor (lb/ft^2): 0.03 note:initial presplit factor should be around 0.1Powder Factor (lb/ton): 0.01 0.40 0.40 0.66

Energy Factor (kcal/ton): 4 162 162 268


Design Worksheet


In the Pattern Design section the following information is required or calculated:

Blasthole Diameter – enter the blasthole diameter drilled.

TC Borehole Pressure – this calculated value represents the borehole pressure of the top charge.

CC Borehole Pressure – this calculated value represents the borehole pressure of the column charge. When presplit techniques are used the borehole pressure should be below the compressive strength of the rock.

Blasthole Angle (deg) – enter the angle the blasthole is drilled in degrees, 0 degress is vertical.

Drill Offset at Toe – this calculated value represents the horizontal distance from the collar of the blasthole to the bottom of the blasthole. It is calculated using the hole angle and bench height.

Top Overbreak – enter the amount of anticipated back break at the top of the hole.

Bottom Overbreak – enter the amount of anticipated over break at the bottom of the hole.

Batter Angle – this value represents the angle of the bench face based on the angle of the blasthole and the top and bottom overbreak dimensions.

Offset From Slope – the distance the inner buffer row is away from the toe of the bench face

Often the Crest or Modified Production Row face burden is larger at the toe that at the crest. This is typically the result of the overbreak from the previous blast or the excavation technique used. However, this distance is critical to the success of the blast design. The top and bottom face burdens must be defined as part of the design process.


Design Worksheet


Top Face Burden – enter the distance from the collar of the Crest or Modified Production Row and the crest.

Bottom Face Burden – enter the distance from the bottom of the Crest or Modified Production Row and the toe.

The distance between the free face (assuming a straight face) and the top and bottom of the modified production row is shown in the face confinement box.

Feet Charge Dia.

Top 13.8 16.8Bottom 24.0 29.2

Face Confinement

Ideally, face burden should be between 18 and 26 charge diameters to provided adequate relief without excessive flyrock.

Free Face Angle – the angle of the free face is calculated using the top and bottom face burdens and the blasthole angle.

Burden – enter the horizontal distance between rows of blastholes measured at the collar.

Bench Top Width – this calculated value represents the horizontal distance from the top overbreak to the crest. It is calculated using the burden dimensions of each row and the top overbreak dimension.

Bench Botttom Width – this calculated value represents the horizontal distance from the bottom overbreak to the toe. It is calculated using the burden dimensions of each row and the bottom overbreak dimension.

Spacing – enter the horizontal distance between holes in a row.


Design Worksheet


Airdeck – air decks are commonly used to reduce the charge weight and borehole pressure in the blasthole. Enter the length of the blasthole that is unloaded and unstemmed.

Deck Diameter (in) 5.5

Deck Length (ft) 4

Deck Cost ($/ea.) $2.00

Deck Compression (%)

Number of Decks per Hole 1

Effective Deck Length (ft) 1.24

% Charge Reduction 5%Deck Cost ($/per hole) $2.00

Air Deck Calculation*

The Air Deck Calculation can be used to calculate the effective deck length and % charge reduction for various sizes of air decks. This is helpful when the air deck diameter is less that the hole diameter.

Subdrill or Standoff – for subdrill enter the distance that the blasthole is drilled below floor level. If the blasthole is backfilled or not drilled to grade enter the distance that the hole is above grade as a negative number.

Stemming – the stemming length is calculated.

Scaled Depth of Burial – this calculated value represents the relative confinement of the column charge. If flyrock, venting or airblast is a concern this value should typically be greater than 1.4.

Blasthole Length – the blasthole length is calculated using the bench height, blasthole angle and the subdrill or standoff dimension.

Presplit Factor – the factor is calculated for the toe or presplit row only. Normally presplit rows are loaded lightly to reduce damage to the wall. When presplitting techniques are used the presplit factor should be around .5 to prevent damage. Higher presplit factors may be required in unfavorable conditions.

Powder Factor (lb/ton) – the powder factor for each row is calculated


independently.

Design Worksheet


Energy Factor (kcal/tonne) – the energy factor for each row is calculated independently.

In the Summary Data section of the Design worksheet the following information is provided:

Summary Data Total Mass Shot (tons): 327,725

Face Energy Ratio at Top 0.62 Required Drill Production (ft): 7,417

Face Energy Ratio at Bot. 1.08 Overall PF (lb/ton): 0.37

Overall Energy Factor (kcal/ton): 151

Post Blast Performance: typical modified production blast with free face

Face Energy Ratio at Top – this is the calculated burden to explosive energy ratio for the burden at the top of the charge of the crest row. This number indicates how confined the face explosives are. If the confinement is excessive the potential for wall damage will increase. If not enough confinement exists then the potential for excessive flyrock increases. The energy ratios needed to provide proper confinement typically range from .65 to .90.

Face Energy Ratio at Bot. – this is the calculated burden to explosive energy ratio for the burden at the bottom of the charge of the crest row. The typical range is .65 to .90. In the example provided the bottom energy ratio is 1.08 which indicates that the toe will be over confined.

Total Mass Shot – this value represents the total tons produced with the current design and blast length.

Required Drill Production – this value represents the total drill production required for the current design and blast length.

Overall Powder Factor – this value represents the overall powder factor produced with the current design and blast length.

Overall Energy Factor – this value represents the overall energy factor produced with the current design and blast length. Wall control blast designers should be careful not to reduce the explosive energy level too far below the normal level required for good breakage. Low energy levels can “bottle up” the explosive gases which can lead to increased block heaving. Energy levels typically should average around 180 kcal/t for normal confinement.


Post Blast Performance – enter comments about the performance of the design here (clean wall, flyrock, backbreak, etc.).

Design Plot Worksheet

Purpose:

The Design Plot worksheet plots a cross sectional and plan view of the current blast design. It is possible to spot design flaws at this stage of the design process.

Operation:

Once the blast design has been entered press the Plot Design button on the Design worksheet.


ProWall - Design Plot

Modified or Trim Blast - Average Conditions 9-May-05

Near Field Ground Vibration

Attenuation Constant (K): 190

Distance Constant (b): 0.90

Charge Weight (lb): 680

Distance Away (ft): 35

Estimated PPV (ips): 18.3

Displacement Analysis

Estimated Face Velocity

Top of Charge (ft/s): 52

Bottom of Charge (ft/s): 27

Estimated Face Displacement *

Displacement Correction: 100%

Top of Charge (ft): 101

Bottom of Charge (ft): 20

* Note: The estimated displacement doesnot consider the "rolling" of thematerial once it hits the ground.This rolling can extend the muckpile well beyond the estimated displacement.

24 ft 24 ft24 ft 24 ft 5 ft

24 ft

24 ft

24 ft

24 ft

24 ft

13.8 ft

Design Plot Worksheet

Operation (cont.):

The Near Field Ground Vibration box calculates the estimated peak particle velocity based on site specific attenuation and distance constants and the charge weight and distance away.


Near Field Ground Vibration

Attenuation Constant (K): 190

Distance Constant (b): 0.90

Charge Weight (lb): 680

Distance Away (ft): 35

Estimated PPV (ips): 18.3

The Displacement Analysis estimates the face velocity and displacement of the face adjacent to the top and bottom of the charge.

Displacement Analysis

Estimated Face Velocity

Top of Charge (ft/s): 52

Bottom of Charge (ft/s): 27

Estimated Face Displacement *

Displacement Correction: 100%

Top of Charge (ft): 101

Bottom of Charge (ft): 20

The estimated displacement does not include the “rolling” of the material once it hits the ground. This rolling can extend the edge of the muckpile to well beyond the predicted range. The displacement prediction can be fine tuned by quantifying the face burdens prior to blasting and measuring the displacement range of the muckpile. By entering the actual field information into the Design worksheet and plotting the design the displacement range can be predicted more accurately.

If the material actually exceeded the predicted range then the Displacement Correction value should be increased until the displacement measured and the maximum predicted displacement match. This Displacement Correction value can then be used to estimate the displacement of future designs.

Cost Worksheet

Purpose:

The Cost Worksheet allows the cost of the design to be calculated.

Operation:


Once the blast design has been entered and the design plot reviewed press the Goto Cost button to open the Cost Worksheet. The screen will look similar to the one shown below.

ProWall - Cost Analysis

Modified or Trim Blast - Average Conditions Designed on: 9-May-05

Slope Design



Batter Angle (deg): 65.0 Compressive Strength (psi): 12,000


Blast Length (ft): 1,000 Batter Slope Height: 40

Staggered Pattern (y or n): y Blast Adjacent To Berm? (y or n) y

Drilling Costs Toe or Presplit Inner Outer Crest or Modified



Holes Required: 42 42 42 42

Production Required (ft): 1,667 1,917 1,917 1,917

Drilling Cost (ft): $1.25 $1.25 $1.25 $1.25

Drilling Cost ($/row): $2,083 $2,396 $2,396 $2,396

Total Drilling Cost ($): $9,271

Total Drilling Cost ($/lft): $9

Explosives Costs Toe or Presplit Inner Outer Crest or Modified



Toe Charge Weight (lb/hole):

Toe Charge Cost ($/lb):

Toe Charge Cost ($/hole):

Total Toe Charge Cost ($):


Column Charge Weight (lb/hole): 680 750 750 750

Column Charge Cost ($/lb): $0.140 $0.140 $0.140 $0.140

Column Charge Cost ($/hole): $95.20 $105.00 $105.00 $105.00

Tot. Column Charge Cost ($): $3,967 $4,375 $4,375 $4,375

Initiation System Type: Nonel Nonel Nonel Nonel

Units per hole: 1 1 1 1

Cost ($ per unit): $7.00 $7.00 $7.00 $7.00

Primer Type: 1 lb 1 lb 1 lb 1 lb

Units per hole: 1 1 1 1

Cost ($ per unit): $3.00 $3.00 $3.00 $3.00

Total Initiation Cost ($): $417 $417 $417 $417

Explosive Cost ($/row): $4,383 $4,792 $4,792 $4,792

Total Explosives Cost ($): $18,758

Total Explosives Cost ($/lft): $18.76

Labor Costs Toe or Presplit Inner Outer Crest or Modified


Labor Cost ($/hole): $10.00 $10.00 $10.00 $10.00

Labor Cost ($/row): $417 $417 $417 $417

Total Labor Cost ($): $1,667

Total Labor Cost ($/lft): $1.67

Cost Worksheet

Operation (cont.):

Enter the cost information for the design in the appropriate fields. Once the design has been entered the Cost worksheet calculates the overall cost of the design, the total cost per metre of wall and the total cost per tonne of rock.


In addition the costs for drilling, explosives and labor are broken down into percentages of the overall cost as shown below.

Summary - Cost Data Total Cost ($) Total Cost ($/lft) Total Cost ($/ton) % of Overall Cost

Drilling Cost $9,271 $9.27 $0.028 31%

Explosives Cost $18,758 $18.76 $0.057 63%

Labor Cost $1,667 $1.67 $0.005 6%

Miscellaneous Cost:

Overall Cost $29,696 $30 $0.091

After the cost information has been entered press the Save button to save the design and cost information in the database.

Timing Worksheet

Purpose:

The purpose of the timing worksheet is to plot the hole pattern of the design. This plot can then be printed out to assist with the development of the initiation sequence. No data entry is required for this worksheet.

Database Worksheet

Purpose:

The Database worksheet is used to store blast designs for future reference. Blast designs in the database can be compared to other designs and re-entered to evaluate the design.

Operation:

The Database worksheet can be opened by pressing the Goto Database buttons in the Design or Design Plot worksheets or by selecting the Database tab at the bottom of the screen. When the worksheet is opened it will look like the illustration on the following page.

Database Worksheet

Operation (cont.):


The following buttons are included with the Database workbook.

Clear All – when this button is selected all of the data will be cleared out of the database. Warning – this is not undoable!!

Load for 1st Comparison – this button is used to load a design into the Design Comparison worksheet. To load a design, select the operation field of the design you want to compare and press the Load for 1st Comparison button.

Load for 2nd Comparison – this button is used to load a second design into the Design Comparison worksheet. To load a second design, select the operation field of the design you want to compare and press the Load for 2nd Comparison button.

Plot Design – used to load and plot an existing design from the database. First select the operation that you want to plot then press the Plot Design button.

Clear One – select the operation that you wish to delete then press the Clear One button. Warning – this is not undoable!!

Parameters Worksheet

Purpose:


To provide an illustration of the variables in the Design worksheet. There is no user entry required for the Parameters worksheet.

Design Data Worksheet

Purpose:

The Design Data worksheet is a protected, internal calculation worksheet. No user information is contained on this sheet and it should not be altered.

Initial Blast Design

Begin the blast design process by filling out the information in the Slope


Design section. Next decide if the design will have two, three or four rows. If the blast has only two rows enter the information into the Toe or Presplit Row and the Crest or Modified Production Row. If the design has three rows fill in the Inner Buffer Row data along with the two rows mentioned above.

Design Considerations

Introduction

Efficient wall control blast design can be defined as achieving a safe and stable slope for the lowest cost possible. Basically the time and effort spent in developing and implementing efficient designs is insurance against future wall failures. The question is, “How much insurance do you need”? The answer to this question is not always clear, but is related to site factors that include:

geology and water conditions slope design life of slope (1 year, 5 years, forever?) value of the excavation

From a production viewpoint the goal of wall control blasting is to make the transition from a well fragmented rock mass to an undamaged slope in as short as distance as possible. This can be quite challenging due to the many factors that influence wall damage. To develop efficient designs one must have a basic understanding of wall failure mechanisms as well as the limitations of the various wall control procedures. In addition, it is imperative that the design be precisely implemented, evaluated and refined on a continuous basis.

Factors That Influence Wall Stability

There are four major factors that control wall stability. They are: geology slope design blast design operational control over the implementation of the design

Obviously, the geology of the site will influence both the slope and blast designs. It is important that close attention be paid to the geological conditions of the wall at the blast site to develop blasts that will limit damage. The key geological influences are the rockmass structure and strength.



Factors That Influence Wall Stability:

When evaluating the structural integrity of the rockmass the type, size, persistence, orientation (strike and dip), in-fill and fracture frequency of the defects must be taken into account.

The strength of the rockmass under shear, tensile and compressional loading will also dictate the overall stability of the slope.

In most cases the final slope design is modified during the excavation process as the site conditions become more understood. In addition, mine plan changes can alter the slope design. The key slope design parameters are; overall height, bench height, batter angle and berm width (which defines the overall slope) and top loading or surcharge.

Several blast design factors influence the stability of the wall including:

• horizontal relief away from the wall• energy concentration adjacent to the wall• blast size and duration

The last major factor that controls wall stability is the field implementation of the mine plan. Even well conceived damage control programs will not perform properly if there is no commitment to quality. Quality, in this case, refers to proper face clean-up, accurate drilling and precise charging of the blastholes.



Blast Induced Damage Mechanisms:

The damage caused by blasting can be grouped into the following three categories:

• stress failure (compressive, tensile and shear)• gas penetration and block heaving• release of load damage

Stress failure occurs when the stress intensity is greater than the strength of the rock. Three generic types of blast induced breakage are compressional, tensile, and shear stress failure. Compressional failure typically is caused immediately around the charge when the rock is crushed by extremely high borehole pressures. During tensile failure the rock is ripped apart by reflecting stress waves. Since rock masses are typically ten times weaker in tension the damage envelope caused by tensile failure can be much greater than compressional failure. Shear failure is controlled by the shear strength of the rockmass, blast duration and blast induced vibration levels. It should be noted that repetitive blasting can reduce the shear strength of the slope to the point of failure.

Another major cause of wall damage is gas driven crack extension and block heaving. As the explosives adjacent to the slope detonate, high pressure gases wedge into structural defects and cause them to expand. The damage done by this wedging action is determined by the strength of the rock and the duration of the pressure pulse. Wedge ProWall v10.5 by Blast Dynamics, Inc. ©1/05

failure can occur as blocks of rock are isolated by intersecting cracks.


Blast Induced Damage Mechanisms (cont.):

Block heaving is another pressure related damage mechanism. Basically, block heaving occurs when the explosive pressure adjacent to the slope is poorly relieved away from the wall. This results in cratering beyond the desired pit limit. Block heaving is also a major factor in damage along weak fault contacts.

During the detonation of explosives adjacent to the slope the rockmass is “loaded” or under compression. When this load is released the rockmass bounces back and can cause separation along planes of weak discontinuity. This type of damage has been observed in excess of 30 metres (100 ft) beyond the perimeter of the blast. Overconfinement of the explosives adjacent to the slope will increase release of load damage.

Wall Control Blast Design:

It is typically not practical or cost efficient to use one type of wall control procedure for every area of the excavation. Instead, the sensitivity and importance of each blast site should be evaluated to assist with the development of the most appropriate design. This evaluation should include:

rockmass strength (compressive, tensile, shear) rockmass structure (defect type, size, persistence, gap, roughness, in-

fill, orientation, and frequency) slope factor of safety water conditions wall importance (final or interim wall) production constraints operational economics drill size, capability, productivity and availability

Once the zones have been determined specific plans can be developed to address the conditions of each blast site. The designs should be continuously refined based on the analysis of each blast’s performance. Ideally the initial blasts should be evaluated in non-critical areas so the design can be refined to match the existing conditions.

There are basically three keys to achieving efficient wall control blast performance. In sensitive zones, each of these keys must be in balance with the others to efficiently protect the wall. These three keys are illustrated on the following page.



Wall Control Blast Design (cont.):

Energy C

onfinement

Energy Level

Ene

rgy

Dis

tribu

tion

OptimumBlast

Perform ance

The distribution of the explosive energy will be based on the charge diameter and blasthole pattern used. Excessive charge diameters can increase slope damage due to uneven energy distribution. In many cases it is necessary to airdeck such holes to improve the distribution of energy and reduce damage.

In wall control blasting the degree of confinement of the explosive energy adjacent to the slope will play a major role in the amount of damage produced. The blast designer should always provide the explosive energy with a path of least resistance away from the wall.

The goal of wall control blasting is to make the transition from a well fragmented rock mass to an undamaged slope in as short as distance as possible. This can be a difficult process that can give blast designers the false notion that to limit blast damage the explosive energy must be minimized, which can adversely effect excavator productivity. In reality, the designer should be developing (for the most part) designs that direct the explosive energy away from the wall while providing satisfactory fragmentation.

Four methods are generally used for wall control blasting. The methods are:

modified production blasts


trim blasts pre or mid splitting line drilling



Modified production blasting is most successful in competent rockmasses or on slopes designed with a high factor of safety. The primary disadvantage of modified production blasting is that the wall is not protected from crack dilation, gas penetration and block heaving. In modified production blasting the energy level is decreased adjacent to the wall to reduce overbreak.

This is often achieved by simply reducing the charge weight (30 to 60%) in the row nearest the slope as shown here (included in the database as Modified Production Blast – Favorable Conditions).

However, most rock types require additional design modifications to minimize damage. These modifications can include air decking, reducing the burden and spacing dimensions (by 25%), minimizing subdrill and increasing the delay interval between the last two rows of blastholes. These potential design changes are shown below (Modified Production Blast, Unfavorable Conditions).




When modified production designs are used the excavator digs beyond the last row of blastholes. As a result one of the key elements in the success of modified production blasting is standoff of the last row of holes. The blasthole standoff is the distance from the last row of holes to the final slope. This offset controls both the wall stability and ease of excavation of the toe. The optimum standoff distance will depend on the strength and structure of the rockmass and should be determined by carefully analyzing blast performance.

The following guidelines are for initial modified production designs:

locate the modified production row 1 metre out from toe of the slope reduce production charge weight by 50% in the last row use air decks and minimize the stemming length in the last row minimize subdrill when drilling adjacent to the next catch bench reduce the burden and spacing of the last row by 25% increase the timing between the last two rows of holes

These guidelines were developed for a wide range of rock type and structural considerations. The performance of this initial modified production design should be evaluated in terms of overbreak, diggability and cost. In some cases it may not be necessary to apply all of the recommended design modifications to achieve good results.

While modified production blasting generally provides the best excavator productivity of the wall control methods, it is unlikely that it will be suitable for all of the rock types and structures within the excavation. In most modified production blasts the explosive energy in the last rows of blastholes is overconfined and will damage weak or sensitive walls.

The second method for wall control is trim blasting. Trim blasts are generally used for rockmasses that are too sensitive for modified production blasting. Three types of blast holes are used; trim, buffer and modified production holes. In order for trim blasting to perform as designed a free face must be established to fragment and displace the rock horizontally away from the wall. If the free face does not exist the explosive energy’s path of least resistance will be uncontrolled and wall damage can be excessive. A typical trim blast for favorable conditions is shown on the next page. This design is included in the database as Trim Blast, Favorable Conditions.




It is advisable to use air decking in at least the trim row to improve energy distribution and reduce backbreak. Air decks may also be required in the other rows to compensate for the reduced burden and spacing dimensions.

The graphic below shows the type of modifications that may be required for trim blasts in unfavorable conditions.

The critical design elements for trim blasting are:• standoff of trim row from toe of slope (dictated by rock strength)• catch bench width (dictates buffer row locations)• subdrill depth (particularly important adjacent to the bench crest)• trim row spacing is typically less than the burden dimension • face burden (horizontal relief)• bench width to height ratio (should be less than 2)• timing configuration• overall energy level (depends on rock strength)• energy distribution (trim row may require airdecking)

trimrow

innerbufferrow

outerbufferrow

face anglearound70 deg

typicalproduction burden

reduced chargein trim andouter buffer rows

stemming

plug

air deck

no subdrillunless the rockis very hard


The following table illustrates initial trim row design parameters:

Blasthole Diameter mm (inch)

Loading Densitykg/m (lb./ft)

Burden m (ft)

Spacing m (ft)

76 (3”) .5 (.35) 1.5 (5) 1.2 (4.0) 89 (3.5”) .7 (.45) 1.7 (5.5) 1.4 (4.5) 102 (4”) .9 (.60) 2.0 (6.5) 1.7 (5.5) 127 (5”) 1.3 (.90) 2.4 (8.0) 2.0 (6.5) 152 (6”) 1.9 (1.3) 2.9 (9.5) 2.4 (8.0) 171 (6.75”) 2.5 (1.7) 3.4 (11.0) 2.7 (9.0) 200 (7.87”) 3.4 (2.3) 3.8 (12.5) 3.2 (10.5) 229 (9”) 4.9 (3.3) 4.4 (14.5) 3.7 (12.0) 251 (9.87”) 5.9 (4.0) 4.7 (15.5) 4.0 (13.0) 267 (10.62”) 6.8 (4.6) 5.0 (16.5) 4.3 (14.0) 311 (12.25”) 8.1 (5.5) 5.5 (18.0) 4.6 (15.0)

The table on the previous page was used to develop the following trim blast design. If a 200 mm (7.87 inch) blasthole is used on a 15 m (49 ft) bench the trim row would contain 51 kg (113 lb.) of explosives and would have a burden of 3.8 m (12.5 ft) and a spacing of 3.2 m (10.5 ft). Due to the relief provided by the free face trim blasting should perform better than modified production blasting in unfavorable conditions. However, since the trim row is detonated last gas penetration and crack extension may still cause excessive damage. The next design option is presplit blasting.

Presplitting blasting consists of a row of lightly charged, closely spaced holes adjacent to the final slope that is fired prior to the detonation of the other holes. This creates a breakage plane to vent explosive gases and reduce crack propagation. A typical presplit blast in favorable rock is shown here.


outer bufferrow

modifiedproduction row

angle drillledpresplit

70 degface angle

no subdrill on benchunless rock is very hard

standoffdistance

inner bufferrow

15 - 30 deg

In most rock types the presplit blasthole should be angled to achieve a more stable wall. The angle selected should be based on the slope design, rock structure, drill type and charging requirements of the blastholes.

The key factors that control the success of presplitting are:

• drill accuracy• geological structure, hardness• presplit spacing• presplit charging• standoff distance of inner buffer row• face burden (horizontal relief)• bench width to height ratio (should be less than 2)• timing configuration• overall energy level

As conditions become more challenging the presplit design will have to be modified to produce satisfactory results. In hard rock masses a short “stab” hole is often required between the inner buffer and the presplit to achieve adequate fragmentation. Subdrilling may be required to establish the proper bench grade when the rock is hard. If the rockmass is highly structured and relatively weak, air decks may need to be used in the buffer rows. The following illustration outlines some of the modifications required for presplit blast design in unfavorable conditions.

Figure 10. Presplit design in unfavorable conditions

One of the key elements of presplit blast design is the charging of the presplit row. Normally the charge is decoupled to reduce the borehole pressure to well below the compressive strength of the rock. This can be achieved by air decking or using a


charge diameter that is smaller than the blasthole diameter.

Air decking is the least expensive method and is appropriate when the rockmass is relatively massive. It typically consists of placing a small bulk charge in the bottom of the hole and leaving the remaining hole open to achieve decoupling. As the rock becomes more structured better explosive energy distribution is required. To improve the energy distribution multiple small explosive decks, continuous small diameter packaged explosive, or in some cases detonating cord can be used. While continuous explosive is the most expensive option for presplitting it also provides the best performance in unfavorable conditions. Unless airblast is a concern, the presplit holes should be left open to reduce borehole pressures and protect the crest region of the hole.


increasing performance in unfavorable conditions

singlebulk deck

multiplebulk decks

multipledecoupled

decks

continuoslow densityexplosive

continuosdecoupledexplosive

airdeck

airdeck

airdeck

chargeplug charge

chargechargecharge

charge charge

The suggested initial presplit design parameters are as follows:

Presplitting can be the most expensive and labor intensive of the wall control methods. However, the long-term benefits can outweigh the costs if a maximum slope angle is required. If the wall is so weak that even well designed presplit techniques cause damage the next wall control consideration should be line drilling.


Line drilling consists of a row of closely spaced holes drilled along the perimeter of the excavation. These holes are left open and not loaded with explosives. The stress waves of the blast create a plane of breakage between the holes. Typically, line drilling is used in very soft material. In hard rock, the hole spacing required is so small that presplitting becomes more cost efficient. Line drilling can be used in conjunction with modified production or trim blast designs. The line drilled row is normally placed between 50 and 100% of the normal production burden from the trim or production row.

Design Implementation

Wall control programs should be established and implemented in a consistent and long term basis. Since it is difficult to analyze the cost/benefit relationship of controlled blasting techniques they are often viewed as an expensive luxury. As a result, many operations fail to implement procedures until the walls start to fail, which results in higher overall costs.

Optimum blast performance can only be achieved with a group effort, as shown below.

Figure 13. Group approach to achieving optimum blast performance

If one individual does not perform their job properly it will effect every individual that follows in the process. In addition, if the design is not implemented accurately it will be


difficult to refine the plan based on its performance.

The keys in implementing this group approach to blast optimization are:

• provide means for open communication between operations• establish performance goals for each operation• establish and document quality control procedures for the design and

implementation process

• train each group in the appropriate quality control procedures and their role in achieving optimum blast performance

• test for comprehension and conduct field audits to promote consistency in design implementation

• provide feedback forms for each operation to be used for blast refinement

• establish weekly planning meetings for representatives of each group • approve blast plans as a group• monitor each blast (video tape, seismograph)• maintain accurate blast records on a shot by shot basis

Damage Assessment and Performance Analysis

Wall control blasting is a process of continuous improvement. The following factors should be evaluated to thoroughly evaluate the performance of the design:

• overbreak• ground vibration levels• drill production requirements• ease of excavation• cost

Overbreak can be defined as blast induced damage to the bench, crest and slope of the wall. Often this damage can be observed by reviewing the video recording of the blast. Ideally no surface swelling will exist beyond the pit limit and the blast will horizontally displace material away from the wall at a rate that is two to three times greater that vertical movement. The damage to the slope should also be determined by documenting any crack extension and heaving beyond the designed excavation limit.

Excessive ground vibration levels can damage the structural integrity of the wall. It is recommended that a vibration monitoring program be developed to evaluate the intensity, frequency and duration of blast induced vibrations. This program should include a number of seismographs to determine the relationship between distance and the nature of the vibrations produced. If the slope is saturated with water it may be appropriate to include pore pressure gauges to quantify the influence that blast vibrations have on in-situ pressures.


Drilling and excavator productivity must be considered during blast performance analysis. Often the use of wall control techniques will adversely effect production levels. This is due to the additional time required to prepare the face prior to blasting, drill the blastholes, excavate the oversize produced by low blast energy levels and to carefully dig to the pit limit. Production requirements will influence the selection of the wall control method used.

It is suggested that a database be used to track the performance factors of each blast. Included in the records should be the costs for bench preparation, drilling, loading and excavating each blast. Once the cost relationships have been defined for each design option an accurate cost benefit analysis can be performed. This analysis will help to select the most appropriate design for future blasts.

Conclusion

The short and long term profitability of any surface excavation relies on slope stability. This stability can be achieved by establishing a wall control program that includes the following:

• conduct a detailed geological/geotechnical analysis of the excavation • divide the excavation into zones that have various levels of sensitivity• define the “value” of each zone or wall adjacent to each blast site• develop a series of designs to match the conditions of the excavation• draft and document specific procedures for implementing the design • train all related personnel in the application of the procedures and test

for comprehension• audit field procedures • keep accurate blast reports• perform comprehensive blast performance evaluations • establish a database of blast performance data• refine the design based on the performance evaluation• consider the wall control process to be one of continuous improvement

There is no magic involved in developing efficient wall control designs, just careful design development, implementation and refinement.


new prowall manual

Documents

prowall worksheets

prowall program

prowall folder

workbook prowall

prowall softwarefollow

prowall easy

design worksheet

design sheet