Trench excavation in rock

Question

Trench excavation in rock

starray (Civil/Environmental)

(OP)

9 May 14 13:52

I am bidding an 8" sewer line project in granite bedrock. The average depth is 10' with a slope of 1:1. I plan on using a 100,000 lb. excavator (cat 349)with a rock bucket. Does anyone have an idea of production rates or a resource I could find them?

Thanks for your help.

cvg (Civil/Environmental) · Answer 1 · 2014-05-09 14:29:11

why would you assume 1:1 in bedrock? even with blasting or decomposed granite you can get near vertical. without a geologist report, no way to estimate your production rate though

rather than a bucket, recommend you use a rock saw trencher

http://www.trencherq.com/Vermeer-Trencher.php

oldestguy (Geotechnical) · Answer 2 · 2014-05-09 15:16:16

How about drilling and blasting and ordinary equipment thereafter?

miningman (Mining) · Answer 3 · 2014-05-10 14:13:57

Oh yeah, if it really is competent non weathered granite, no way will you excavate without drilling and blasting. Now if its weathered and in general "rotten rock" you may well get down to 8 feet or so with ripping and heavy excavators but that last two feet or so will destroy your economics unless you've made some really heavy allowances for tuff rock conditions. And yes with explosives I can easily get something close to vertical excavation walls but with ripping etc, you'll be at 3:1 or less. Once again tho, productivities are impossible to estimate without detailed drawings.

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Trench excavation in rock