Pools

 

If hammering is not feasible, don’t be afraid of blasting.  Light blasting with small holes is not that big a deal.  If you don’t have too far to go and not too large an area, a blaster can use hand sinker drills to drill out a 3 ft pattern in a couple of days, load about 1/2 to 1 stick of 1-1/4×8 in each hole, and get it all done at once.  Let’s say you have a 20×25 ft area.  That is about 50 1.5-in.-diameter holes which, if not more than about 5 ft deep, can be drilled by a 4-man crew operating two drills in about 2 days. This is the least expensive way to drill a job like that — mobilizing and operating a tracked rig in a small space is a mess and the holes will be too large.  

 

A good start of the drilling will not guarantee a properly located hole because the inherent structure of the rock itself may cause deviation of the hole. However, there are various means to compensate for deviations caused by the rock structure

 

The diameter of the blast holes is normally smaller which provides better distribution of the explosive in the rock and avoids excessive over break outside the theoretical contour.