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Construction & Contractors/Rock blasting Vs Mechanical excavtion


Respected Sir
I have the opportunity to go through your reply to a question on 30/06/2008 on the subject I am interested. I am working on preparing a presentation on comparison of various excavation methods and their cost used, at construction site. I would be very thankful if you could suggest some recent references particularly application of green break technology & mechanical excavation method used at construction site

Thanks & Regards

By "green break technology" I presume you are referring to the use of expansive grouts, like Da-Mite or Dexpan, or the use of hydraulic splitters?

I don't know of any nice discussion you can use without doing any research on your own.  You will need to do some work.

The first question to be answered is whether the material is amenable to mechanical excavation.  For that, I would suggest the Caterpillar Handbook which gives criteria for mechanical ripping based on seismic velocity.  The Caterpillar people also  have information on hydraulic hammer productivity and ripping productivity for different rock types.  Often the decision on mechanical excavation is based on cost limitations or production quotas (calendar time).  

There are references in the literature that you should be aware of regarding modifications to rippability criteria that take the fracturing and ripping direction into account.  For example, heavily-calcareous soils (caliche) can be very difficult to rip because of the lack of fracturing and because they are not brittle, even though they are not dense and the seismic velocity is not that high.

For applications of green break technology, you need to consult the manufacturers.  There are many differences in the application of different expansive grouts; you need to account for differences in material type and ambient temperature.  A grout that works well in one place will not work as well in another.

The main difficulty you are going to have is in costs.  You will quickly find that there is no comparability in the presentation of unit costs for excavation using these different methods, even if you can find information.  For example, what if you find out that blasting costs $2.00/cu m and ripping costs $5/cu m?  Which is cheaper?  Well, if you only have 1,000 cu m to do and it takes 2 months to get permits and mobilize a blasting crew, perhaps ripping is actually cheaper.  What if it's the reverse $2.00 to rip and $5 to blast?  In that case ripping may be more expensive if your daily production requirements are more than you can produce by ripping.  My advice would be to decide on a daily cost of construction (men and equipment dedicated to the excavation) and then look at the differences in cost on a productivity basis, then adjust for the size of the plant and equipment from there.

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Robert Cummings, P.E.


I can answer questions related to rock blasting, rock and soil excavation (such as tunnels and highway cuts), stability of such excavations, and foundations in rock and soil. I can also answer questions related to geology and mining.


30+ years as a geotechnical engineer and minerals engineer. Active consulting practice in rock blasting, geotechnical engineering, and rock mechanics for mining and heavy construction.

Society of Mining Engineers, Deep Foundations Institute, Association of Engineering Geologists, and International Society of Explosives Engineers.

Mining Engineering, AEG Bulletin.

BS and MS Geological Engineering

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