The maximum depth that can be tested using Pile Integrity Test depends on many factors, and it is normally linked to the slenderness ratio L/D. 

Preferred slenderness ratio L/D for pile integrity is around 30, but in some cases this ratio may exceed 30 (hard soils), even reaching 60 (very soft soils).

However, this ratio can be sometimes lower and sometimes higher than 30, as pile integrity check depends a lot on several factors:

• Skin friction: very high soil resistance can reduce the maximum length
• End bearing: very rigid soil or rock may result in an unclear toe reflection. To have a good reflection wave the soil stiffness should be considerably weaker than the foundation
• Very long large diameter piles: the attenuation of the wave due to the soil resistance may create difficulties detecting the toe reflection

Also, the type and size of the hammer to be used is important. For very long piles, we recommend to use a bigger hammer than the one we offer in our kit.