Blasting Bedrock Next to Existing Structure
Blasting Bedrock Next to Existing Structure
(OP)
I have an existing medium-rise building with a one level basement. This building is founded on bedrock just below the basement slab.
The owner wants to put a new structure right next to the existing, with a two level basement.
Now, this will require the removal of bedrock, wether by blasting or chipping. I think that this rock removal will fracture the bedrock under the existing building, possibly causing undermining the foundation. I want to have the owner pull his new structure away from existing X amount of feet.
Does anyone know of any problems associated with removing bedrock 13' down from face of existing structure founded on rock? And what is a safe distance to move the new rock cut away from existing structure?
The owner wants to put a new structure right next to the existing, with a two level basement.
Now, this will require the removal of bedrock, wether by blasting or chipping. I think that this rock removal will fracture the bedrock under the existing building, possibly causing undermining the foundation. I want to have the owner pull his new structure away from existing X amount of feet.
Does anyone know of any problems associated with removing bedrock 13' down from face of existing structure founded on rock? And what is a safe distance to move the new rock cut away from existing structure?






RE: Blasting Bedrock Next to Existing Structure
Upon excavation, the released of restraint adjacent rock sometimes expands -what by the way affects a little the adjacent building- and it may be then interesting to delay construction of the wall or allow 100 mm or more of compressible material in-between of our new basement walls and rock.
Although not extense in the subject, you can give a look to
Rock Engineering Applications
Franklin and Dusseault
Mc Graw Hill
RE: Blasting Bedrock Next to Existing Structure
RE: Blasting Bedrock Next to Existing Structure
RE: Blasting Bedrock Next to Existing Structure
Someone told me of a procedure like blasting - The rock is drilled (like blasting), but instead of using explosives, the drill holes are pressure injected with water, and when the pressure is high enough the rock fractures. Anyone hear of this? Doesn't seem that possible, because what about fissures and such in the rock?
RE: Blasting Bedrock Next to Existing Structure
RE: Blasting Bedrock Next to Existing Structure
RE: Blasting Bedrock Next to Existing Structure
blasting and reduces the amount of shock waves produced.
RE: Blasting Bedrock Next to Existing Structure
I agree with Visitor, use delays and above all do a crack survey of all surrounding buildings, the claims for cracks will come in thick and fast at the sound of the first charge.
A Geotech shoould be consulted to ensure that joints and faults dont provide any unpleasant surprises and monitor all blasting with seismic apparatus just for records.
RE: Blasting Bedrock Next to Existing Structure
You may want to try the International Society of Explosives Engineers - I think they are at www.isee.org - to find a blasting specialist in your area.
RE: Blasting Bedrock Next to Existing Structure
Production blasts should advance to the third line from the line drill holes.
If the rock dips toward the face the rock may have to be pinned or rock boltsd to prevent slippage in the rock that supports the adjacent building.
References:
ISEE,"Blasters Handbook", 17th Edition,International Society of Explosive Engineers, 1998,http://www.isee.org.See Chapter 31, pages 479 -506,Controled Blasting.
Berta,"Explosives: An Engineering Tool",Italesplosivi-Milano Italia 1990, Chapter 3, Pages 77-108
Konya & Walter,"Surface Blast Design",Prentice-Hall,1990,Chapter 10,Controlled Blasting, pages 217-238
Persson,Holmberg & Lee,"Rock Blasting and Explosive Engineering",CRC,1994,Chapter 9,Contour Blasting,pages 265-285.