Rock Excavation Info Needed 3

[jnemesh]

Can anyone point me in the direction of some useful info on unit costs and production rates for bedrock excavation/grading?

The site is in upstate new york with limestone bedrock. The project is to rough grade the bedrock over approximately 16 acres at thickness ranging from a few feet to 15-20 feet (400,000 CY).

Given the size and extent of the rock, does it make any sense not to blast (assuming vibration, noise, etc. are not an issue)?

As a side question, how accurate, in terms of depth, can you get with blasting? For a target 15 ft rock removal, would you end up blasting deeper?

 

[BigH]

Your best bet would be to get hold of a general contractor in the area. I used to find them quite useful in gaining a "estimate" of costs. They would know the usual way to handle the excavation, haulage, etc.

 

[concretemasonry]

Costs and production rates vary wildly depending on the characteristics of the rock especially if it is fractured. Fractured rock, if not able to be ripped, can require a lot of drilling and explosives because the fractures absorb so much energy and can be erratic and require a wider range of protection from "fliers"

Fairly sound rock (usually deeper) is much more predictable and less drilling (wider pattern) and explosives are required.

A local contractor will be the best source of information when it comes to costs and production rates.

On on project I was responsible for, a local contractor was about 20% below (planned quantities for volumes) the big contractors (MK, Kiewit)on a 2,000,000 yard rock rough excavation and finished well ahead of schedule and it was a total winner and secured him many future jobs (rock, dirt, compacted fill & excavation)on the over-all plant project.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[msucog]

bigh and concretemasonry are some of the best sources here. be aware that blasting is an art...sometimes the blasts do crazy things. i've seen it go 20 deeper than planned...was ugly. i've also seen blasting contractors say they plan to blast to say 20' deep...then once i point out that i'm there to quantify depths and that they get paid for 'neat' volumes, they suddenly change that to 12' deep.

for that depth of rock removal, it sounds like someone will spend a hell of a lot of time with rock hammers. makes sense to blast. if the owner is worried about blast litigation, then suggest beefing up their blast monitoring to mitigate litigation.

 

[cvg]

before you can estimate the costs, you will need a blasting plan. In general, the contractor should be required to submit one and you should verify the qualifications and experience of the blaster. You also need a geologist to characterize the site, otherwise it will be difficult for the blaster to plan the work.

Costs will depend on types and pattern of drilling, amount of explosives needed, quality of the rock, bedding angles etc. Also, there could be a big cost involved with processing the rock. Will it come out in small fragments, or large boulders. How fast can it be loaded and moved? Where is it being hauled to and can it be used on site or elsewhere? How long will the drilling and blasting crew have to sit around while the rock is being hauled off? What kind of permits are required? Will it require traffic control? Is there any nearby roads that would need to be shut down during blasting?

I suggest if you want a good estimate, sit down with your geologist, blaster and contractor and work through the issues.

 

[Dozerman56]

If you've got a geotechnical report and a grading plan I'm sure you can get a local heavy/highway contractor to give you pricing.If the abutting properties are developed,any information available would be handy. Different areas have different requirements regarding proximity of blasting to existing structures.

What are you going to do with the shot rock? If you're going to re-use it as fill, it'll probably need to be crushed. Crushing isn't free but neither is loading it into trucks and hauling it off.

 

[msucog]

one last passing thought: sometimes the contractor can mobilize a very large piece of equipment capable of digging rock depending on the rock type, bedding plane, hardness, etc. while it is expensive, it may alleviate some of the other concerns.

 

[miningman]

Msucog's post is true , but i've always been of the opinion that explosives are an extremely cheap form of energy. But then Im one of those individuals who use the stuff on a daily basis and the practicalities of dealing with nervous customers / engineers/ neighbours etc etc dont intimidate me