You have to be careful with production rates units: 2 hours/M3 or 2 M3/hour? In the first case: 500M3*2hours/M3=1000hours Those are crew-hours or man-hours, depending on how the production rate is stated. 1000 crew hours can be acomplished by 1 crew in 1000 hours or by 1000 crews in 1 hour. But there's a phisical and practical limit to the number of crews you can assign to a particular job: the 500M3 pour in question. That's where you need experience and common sense to determine the right number of units (crews) to assign. This logic has it's limits. Somebody once said that if all thing where like this, then you could acomplish an activity called pregnancy assingning 9 women for a month instead of one woman for 9 months.

I don't think you can estimate the number of resources per activity per se because resources depends largely on the type of activity. Ex. if you want to estimate a concreting activity your resources would be cement, sand, labor, mason etc. but if your activity is getting a construction permit your resources would be the laison officer only who would follow up this permit. When you're talking of construction activities, I advised you to pick some estimating books or for comprehensive use get a copy of RS Means. These references would give you an idea what are the resources needed for a specific activity. Hope this would help.