Rock Blasting vs. Breaking

[LJDub]

I am involved in a project that is required to remove two dozen large sandstone boulders from a location that is about 100 meters downstream from a major dam. These boulders are approx. 10m x 5m x 3m in size. Would it be better to remove the rocks by breaking them into smaller sizes using blasting or rock breaking methods? Additional considerations/concerns are seismic activity on the embankment dam, economics, length of project, etc. Any thoughts would be helpful.

Thanks in advance.

 

[cvg]

you should have no problem with the dam, blast away. however, before blasting get qualified blasters and approve the blasting plan which should include PPV monitoring.

just finished with blasting on a dam spillway less than 10 meters from the top of an existing dam with lake full to the spillway crest. no problems encountered.

 

[LJDub]

Blast away it is. Thanks cvg for the help.

 

[cvg]

another suggestion, if you are not the dam owner - then as a courtesy and to reduce liability, notify the dam owner of your plans well in advance of your blasting. they may wish to review your blasting plan or provide additional seismic monitoring on the dam

 

[dik]

And also do a pre-blasting review of the existing conditions.

Dik

 

[cvg]

if you are concerned with any structures within the blasting vicinity that could be damaged or claims may be made that you damaged them, conduct a video / photo inspection with the owner present and give them a copy prior to blasting. this should focus on any existing cracks, settlement etc that could later be blamed on your blasting

 

[racookpe1978]

Your blasting plan should include position of the charges with respect to the different sized boulders: It seems obvious, but consider the difference in affect of the blast on the nearby dam if (1) you place the charge next to the side of the boulder (near its "equator", for example) or inside a hole in the rock and blasting the energy sideways into the rock and soil; compared to drilling underneath the boulder's mass and placing the charge so more of the energy goes "up": lifting the rock's mass upwards as it breaks it into pieces.

The surrounding dirt around the charge reflects energy both cases, but blowing the debris "up" reduces the total energy into the surrounding soil ...and the dam.

(Blowing "up" requires you plan on retaining the debris however.)

You may also consider drilling a row of holes in the larger boulders before the blast to encourage cracking into manageable sized chunks rather than random crack parts.

 

[LJDub]

Thanks for all of your thoughts. There are still a lot of items we are taking into consideration, including setting up seismic monitoring equipment at the dam, any necessary traffic control (major road 150 meters away), alternative methods of demolition, environmental concerns (located near a water way), blasting permit requirements, and ..... So all of your input definitely helps.

 

[BigHarvey]

If you have problems with blasting , you can use alternative methods such as :

- expansive cement ( Bristar, S-mite, etc )
- Nonex, Boulder buster or Pyroc products ( heat gives very high pressure which will break the rock, no vibrations ).