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Tutorial of I-Blast software

User’s Guide 2 : Seismic Analysis

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I-Blast 4 – Tutorial

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User’s guide 2 : Seismic Analysis

Tutorial of I-Blast software 2/98















Sommaire

I. Import a seismic record 6

A. Import 6

a) Auto import 6

b) Manual import of a record 40

B. Filtrage d’un signal 50

a) Low Pass Filter 52

b) Band Reject Filter 56

c) Band Pass Filter 60

d) High Pass Filter 62

C. Compare maximum vibration levels 66

a) Compare with standards 68

b) Compare to perception thresholds 74

II. Determining a delay minimizing vibration 76

A. Case 1 : Delay between holes of a same row 78

a) The case of 2 holes 80

b) Case of n holes 84

c) Case involving several seismic acquisition stations 88

B. Case 2 : Delay between multiple identical rows 96






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I. Import a seismic record

A. Import

a) Auto import

In « Records » click on « Seismic », the « Seismic records » window appears (A),

Click on to create a new record

Default, type of a new record is defined as « Full blast », there is no information in the fields « Zone » and « Info » and all data on the right equal 0.00.






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Now, you have to define all the parameters of you’re blast record

1. Indicate the « Reference Distance » (distance between, blast center and zone center) and the « Reference Charge » for the selected record.

2. Valid each field content by typing on the enter key.

3. Type : Choose between « Full blast » and « Single hole » on the « Type » drop-down menu..

In this example we will take a reference charge of 24,0 kg and a reference distance of 400,0 m. In a full blast case, reference distance will be automatically calculated by I-Blast.

When you import a record, it can be the seismic record of a full blast (several holes for the most

simple ones) or the seismic record of a single hole (also named Elementary Seismic Signature).

This different types of record are used in some calculations but not in all of them, so I-Blast will

not display the “full blast” ones when they can’t be used. That is why you must define them with

accuracy when you add these seismic records. If you don’t know what type of record is it you

can choose the “?” as type.

- Full blast : Seismic record of a full blast

- Single hole : Seismic record of only one hole

- ? : Seismic record you don’t know the type of






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4. Zone : Choose the zone with the drop-down menu. For this example we choose the “Zone A”. Like that, the record will be assimilated to the center of the chosen zone for the calculation.

Be Careful: Before you can select a zone you have to create one. To create a zone please report to the concerned section in “User’s Guide 1: Design your blast”






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5. Info : Add here some information as you which. It can be the date, the identification number of the blast or any other information. Keep in mind that these information will make your futures research easier.

Creation of the record line is only the first step of the import of a seismic record. You now have to import the seismic signal from your personal files. To do that, there are several possibilities dependent of the type of file you actually use.






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i. Import from a text file (ASCII coding)

1. To import a seismic signal click on

Seismic records have different format depend on the type of equipment used to acquire them. Conversion software of these records has been developed by the enterprises that create these equipments. You can find these software on the website of these enterprise. If you have any problem with the conversion of your files in ASCII Coding, please report to the user’s guide “Seismic record conversion” in the case you used equipment from NOMIS, White Industrial Seismology, or Instantel. In the other cases please contact your provider.






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2. Click on the field Files to browse your folders and select your record file.

3. A window allow you to browse your folders will appear. Select your file and click on

open.

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4. Click on one of these buttons according the type of record file you wish import.

These buttons allow you to automatically archive all the data that are not related to the signal, i.e.

the header and if there is the footer. Each of these buttons can process these signals files if they

were made with the originals settings (indeed, it is possible to add or remove certain information

from the header from conversion software which it was discussed in the previous section).

The buttons on the right side of this window allow manual application of this method we will see in the next section on page 44.






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5. I-Blast load the data and put them in the right format to show you a preview of your

signal.

The S channel located in the bottom frame is the audio channel. All the seismic acquisition stations are not equipped with microphone. In this example there is no sound data. In section “ii”, page 30 of the present user’s guide, you will see another example with a record including sound.






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6. In one of the three graphics L, T, or V zoom in by creating a simple frame around the

part of the signal you want to conserve. Proceed by using the mouse and making sure to

stay within the graph.

Warning : Once you’ve created your frame, when you realese the left mouse button, zoom will

be performed on the time interval so defined and this in all channels L, T, and V.






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7. You can repeat if necessary, and return to the original view by pressing CTRL + 0.

8. Once the signal is framed click on to import.

Why reframe the signal on a time interval shorter ?

When you are scanning one or more records I-Blast software performs a calculation for each point of your registration. By reducing this interval of time you reduce the number of issues. Thus, keeping only the useful signal can perform calculations faster.

In this example the time interval of registration has increased from nearly 6 seconds about 2 seconds which allows for the analysis of this recording at least 3 times faster than if it had been imported into its initial state.











9. Repeat to add more seismic signals






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10. In this example we have 4 records in the same shot, one for each station.






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ii. Importing from a native file NOMIS

In the case of a seismic recording made using a seismograph Nomis it is possible to import the

record from the file directly from the seismic station without having to convert it to ASCII (. Txt

format).

1- To do this click on the icon






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2. You will see a window with a field « file », click in this field to access your Windows

Explorer and select the NOMIS file of the record you want to import. (It may be a .nsz file

for example)

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The contents of your file appears in the frame « File Contents »

3. Click on « Pre-view and Import file » to see the seismic signal and import it

In this frame you can see the data in the textual form that make up the file. The header and shape vary with the type of recording. The data contained in the header provide such number of registration, frequency, date and time of recording, recording time ...






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4. You can crop your signal as explained on pages 21-24 of this document) or import it full

5. Click on to add the record to your shot

Warning: As long as you do not click on your record is not saved as a

record of the shooting and is only a preview






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6. Your registration is now part of the blast you want to associate

Data previously integrated « type » and the associated « zone » are indicated. After importing,

you can directly consult the maximum vibration levels for each channel of any imported record.

In the boxes below you can see the signals on the different channels.






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b) Manual import of a record

In some cases, the signal on its textual format comes from a file with a specific format whose

treatment has not been automated or a known format that has been modified. It should then be

necessary to import it manually.

1. Add an entry in the list, specify the “type” and “zone” etc. (as explained on pages 7 to 12

of this document) and click on






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2. In the window that appears, click in the « File » field to access your File Explorer and

select the folder and record file (.txt or .csv format). You should sse information similar to

the following screenshot.

These information, in the header, about the signal before the signal data itself. Part of this information is displayed on the screenshot.






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3. Under the box « Leave to this zone the lines to import » you must archive or delete all

the text information independent of the signal (whicih would prevent the import of the

signal) .aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

4. Then click on « Select field for each column » to continue the importation of your record.

Different buttons allow you to process these data lines :

- The arrow to the side of the frame « Move to this zone the header lines that

you don’t want to import » can transfer the top line of the central frame in the top

frame. This line will not be reflected in the record.

- The arrow makes the opposite effect when it applied.

- The arrow allow you transfer in the upper box all the lines which are selected

in the centre box with the mouse.

- The arrows a allow you to move the lower lines located in the central

box in the “Move to this zone the footer lines that you don’t want to import” box.

Note: The calibration of the blast and the text at the end of some recording signals are not a problem for the integration of the seismic record. (use the elevator cursor on the right to get to the end of the text file)






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5. You should see a screen similar to the one located on opposite side of this page

6. Use the drop-down menus to specify the nature of data within the visible columns : in

this cas it’s « Time Way », « Way T », « Way V » and « Way S »

At the top of this tab you can see several options: they should be defined properly

- Initially set the decimal separator in choosing either a « . » or a « , »

- Then select the appropriate column separator and automatic mode « Auto » checked

by default if it does not have good data

Once the columns you can see in the main frame to match your seismic record you can proceed

to the selection of field types.

Below this menu selection of field types are other options that are set automatically, but can be

changed if they are wrong.

These are the sampling frequency, the vibration unit (ie mm/s or in/s) and unit of air pressure (ie

PA, millibars or dB).






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7. Once all these settings set you can go to the last tab « Seismic trace preview ».

8. Now you can treat your signal as usually (as explained in pages 21 to 24 of this

document.






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B. Filtrage d’un signal

1- By default, I-Blast software will select the current blast and the first seismic record in the

list

2- In the seismic analysis window, open the FFT – FILTERING tab

Usefulness of the module : Clean signal noise that can affect the quality of analysis to be

carried out thereafter.






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3- Select by ticking the boxes, routes the signal you want to filter

4- There are 4 different filters :

- Low pass : To eliminate low frequency

- Band reject : To eliminate a frequency range

- Band pass : To keep a specific frequency range

- High pass : To eliminate high frequencies

a) Low Pass Filter

1. Click on the chip corresponding to the low pass filter in the filter shape

The filtering of a signal is done by selecting a type of filter and placing the cursor at the

corresponding frequencies.






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2. To apply this filter, move the right slider cursor until the frequencies you want to remove

appear in gray

3. Then click on , you will see your filtered signal on the right of

your original signal.

4. Click on to save the filtered signal.






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5- This signal will bear the name of the original signal argued with additional information

indicating the type of filter used and the cutoff frequency set used

b) Band Reject Filter

1. Click on the chip corresponding to the band reject filter in the filter shape

2. To apply this filter, move the left and right slider cursor until the frequencies you want to

remove appear in gray






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c) Band Pass Filter

1. Click on the chip corresponding to the band pass filter in the filter shape.

2. To apply this filter, move the left and right slider cursors until the frequencies you want to

remove appear in gray









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d) High Pass Filter

1. Click on the chip corresponding to the band pass filter in the filter shape.

2. To apply this filter, move the left slider cursor until the frequencies you want to remove

appear in gray






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C. Compare maximum vibration levels

When you select one or multiple records in seismic analysis, you can compare maximum vibration

levels to various existing standards and different thresholds of perception.

1- Once your signal(s) selected, go to the tab COMPLIANCE

2- The points you can see in the chart correspond to the maximum vibrations levels of the

main frequencies for the three different channels.

- Blue for the Longitudinal channel

- Red for the Transversal channel

- Green for the Vertical channel











a) Compare with standards

Many standards are provisions in this tab

Standard USBM Structural

Standard USBM cosmétique











Standard DIN Haute

Standard DIN Moyenne











Standard DIN Basse

Standard France (10 mm/s)











b) Compare to perception thresholds

Various perception degrees have benne implemented in this module; you can select one or several

Human Response(s) thresholds to display











II. Determining a delay minimizing vibration

This optimization is based on the Single Hole Signature (SH). These SH are the records made in

one or several seismic stations for the blasting of a single representative hole (to increase the

analysis possibilities, it’s recommended to make several holes signatures). These SH can also be

recovered from the deconvolution of a full blast signal. .

The principle used in the analysis described subsequently considers that we are working in far field

simulations using linear superposition. On the other hand, we equate the SH as the seismic

signature of each of the holes that compose the blast we want to optimize the time sequence.

In the menu « Analyze » click on « Seismic »to get the next window,






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Several configurations can be applied to the seismic analysis. The two parameters that we

consider are the number of holes and the analysis type performed between the absolute and the

relative one.

A. Case 1 : Delay between holes of a same row

When you open the seismic analysis window you are ine the « Recording » tab

1- Begin by selecting a single record signature hole and go to the Standard SH analysis tab

to conduct the seismic analysis

You will access the analysis screen

2- The range of delays (in ms) is used to define the maximum delay analysis

3- The number of holes you want to simulate

4- The relative option is useful in analyzing several records at the same time, we’ll see how

it works later in this tutorial L’

In this tab you can access all of your blasts (red frame) and, for the selected blast, you can

access all the linked records (the ones you have import and the filtered ones you have save

previously) (blue frame)

Until you have done any analysis, no information appears on the screen, you can change the

parameters of the analysis you want to perform.






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a) The case of 2 holes

At first it’s necessary to analyze the delay between two holes. This analysis is done by linear

superposition of signature hole records (SH)

1- Once the parameters cited previously defined, click on

2- The graph that appears in the left frame corresponds to the maximum vibration level

simulated for each delay tested.

3- By default the cursor is set at the delay providing the lowest maximum vibration level. In

the case there two delay provide the same maximum vibration level, I-Blast software will

select the lowest of these delay You can select any delay by clicking directly on the

graph.

4- Below the graphic appear different information including the virtual unit load and the

vibration level corresponding to the selected delay.

5- The reference charge, the optimal delay and corresponding vibration level.

6- In the right frame appears a graph corresponding to the different records processed.

When a single record has been treated, there the same result on both graphs. We’ll see

the utility of this graphic in the case we process several records at the same time.

7- Finally the table at bottom right indicates the maximum vibration level of the processed

records for the currently selected delay.

8- Two other tabs provide information on Seismic Analysis, the « Data » tab provides

details of context and vibration levels in response to delays in tabular form. The

usefulness of this framework is that you can copy data from it and paste it into a

spreadsheet to perform your own process as you wish.






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9- The signal tab allows viewing of the simulated signal resulting from linear superposition,

this signal is the linear superposition of many sets of signals and the selected delay.

10- This signal can be save as a new one to be reused in subsequent analysis as discussed

in the section devoted to it later in this tutorial

It is calculated by I-Blast, function of the SH used for analysis and of the selected delay

in the left graph.

To register this signal, enter the name you want to give it in the box at bottom right below

the button and then click on this button.

11- A series of dialog box will follow on the screen confirming your signal is saved

12- and the smooth running of the record file.

To access these data it’s essential to have checked he option « Show Signal » on the default

tab of « Standard SH Analysis »

On the other hand, this option is available only in cases where a single record is selected and

treated.






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b) Case of n holes

1- To perform an analysis taking into account n holes, we just set the desired number of

holes and perform analsis in the same manner as for two holes.

2- After which you’ll see te corresponding data for the analysis of delays on these n holes

(12 holes in the present case)

3- As for the analysis of the 2 holes you can see the chart data in tabular form.

Processing and analysis of data always consist in a linear superposition applies in distant fields

and doesn’t take into account the placement of the holes relative to each other.






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4- And the simulated signal

5- and you can save it by clicking on






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c) Case involving several seismic acquisition stations

You can also perform a seismic analysis to optimize the delay according to several records of the

same blast, made at different stations.

To do this you must select multiple signals using the CTRL ans Shift key on your keyboard.

1- Maintaining the CTRL key to select multiple distinct records one by one.

2- Keeping the Shift key to select a data set one after the other by clicking on the last of

these records.

3- Then open the « Standard SH Aalysis » tab and set your settings as you wish

When you are scanning many records you can choose to perform this analysis in either

absolute or relative mode as we shall see in the following two cases.






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i. Relative mode

1- To analyze this in mind you should first check the « Relative » chip on the right side of

the field used to set the number of holes to be taken into account.

2- Then click on

Several differences can be observed when dealing with multiple signals simultaneously:

3- The maximum amplitude of seismic traces is normalized to 1

4- All the processed signals are shown separately in the right graph

5- In the table showing the maximum levels for the selected delay is obtained the data from

each seismic station (each record)

The analysis with the « relative » enabled will get the optimal delay to reduce maximum

vibration level in all analyzed records. In this case we don’t seek to achieve the maximum

vibration level as for the blast but to reduce vibration at each station.






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ii. Absolute mode

1- To use the mode analysis « absolute » don’t check the box « Relative » on the right of

hole’s number (note : by default this box is NOT checked).

2- Then click on

3- The vibration levels that are observable with this method are the absolute levels, the

maximum for each seismic stations with the selected delay also appear in the table at the

bottom right of the window.

The analysis in absolute values (option « relative » not ticked) will get the optimal delay to have

the lowest maximum vibration level, all records processed, that is to say the whole blast on the

whole seismic station.






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4- You can always access the complete picture corresponding to the graphs of each of the

analyzed records.

5- This type of analysis ca be applied to n holes






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B. Case 2 : Delay between multiple identical rows

We have seen before (A- b) of this part) that we can record any signal simulated from the linear

superposition of a Single Hole Signature (SH), for a manually defined number of holes.

This signal would the correspond to a row of holes signal.

We also saw that we could save this simulated signal and use it to a new analysis like a new SH.

This analysis will provide the optimal delay between 2 to n identical rows.

1- Select the row’s records that you backed up from the holes as seen in the A- b) of the

the part

2- Instead of the hole number, indicate te number of rows that make up your blast. These

rows must be identical (same number of holes and even loading)

3- Start the analysis by clicking on






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4- This analysis, like all those that involved multiple signals, can be made in absolute mode

in order to obtain the maximum vibration levels as low as possible on all the seismic stations.

5- You can also perform this analysis on how to reduce the maximum vibration level

reaches at each station.

6- In the same manner as in the previous analysis you can access the data table by

clicking on the tab « Data ».

Documents

I-Blast 4 Tutorial - dna-blast.com€¦ · Bureaux : 35 Av. Sainte Marguerite, Les roses d’azur B3 – 06200 Nice Tel : +33 (0)950 44 55 43 – Fax : +33 (0)955 44 55 43 Email :