Hydraulic Impact Hammer
Feasibility & Performance

How do impact hammers (hoe-rams) work? 

There are two types of breakage to consider, namely:

1. Primary breakage and

2. Secondary breakage.

Primary breakage in rock excavation by hydraulic impact hammer is rare.  Primary breakage is only possible in weak intact rock containing extensive latent weaknesses such as fissility, bedding planes, or other surfaces of considerable weakness that will surely fracture and separate under hydraulic impact hammer loading or during rock intact property testing.

Secondary breakage is most common in rock, relying on discontinuities (actual breaks and in most cases, separations in the rock).  As such, the RQD may be used to predict performance.  However, the use of discontinuity spacing below the top of rock and a function of depth promises to be a much more reliable method for determining hydraulic impact hammer feasibility.

How to predict performance? ..... Power Point Presentation

What geotechnical parameters determine hydraulic impact hammer performance?

There are two categories of rock properties to consider, namely:

1. Intact rock properties and

2. Mass rock properties.

What geotechnical parameters determine hydraulic impact hammer feasibility?

The most effective method for predicting impact hammer performance is to use RQD, sonic, and seismic velocity by depth below the top of rock.