Equipment damage during SPT

[benjaman]

Hi,
we are doing Standard penetration Test for a depth of 35. The rope controlling the hammer gave away after reaching a depth of 22m.

My question is can we still continue with the same bore hole for the remaining depth after the equipment is repaired?

 

[Ron]

Yes. The rope is just a means to lift the hammer. It shouldn't impede its free fall. The driller will have to adjust his technique slightly to accommodate the new rope, but they do that routinely. A new rope has increased friction on the cathead, so the hammer will be easier to lift, initially. This will cause a tendency to overlift the hammer.

If you have questions, do a stress-wave energy test on the rig using ASTM D4633. This can be used to compare different drill rigs and operators.

 

[BigH]

And, watch the number of turns the driller has on his cathead. Should be 1-1/2 if my memory serves me right.

 

[Ron]

BigH...that's right...no more than 2-1/4. (per ASTM D1586, anyway)

 

[YannisChasiotis]

I don't get it...Why did you think you needed a new borehole?

Also, I do not trust SPT results after a depth of 30m or so...