Dial Penetrometer

[lcruzz01]

I'm interested in buying a pocket penetrometer so I've been searching the web and found a dial penetrometer with the following description: "...used to evaluate the angle of internal friction “j” of sandy soil and the cohesion “c” in clay soils." I thought penetrometers were used only to obtain the unconfined compressive strength of clayey soils. Anybody has experience with this type of penetrometer and how reliable are the angle of friction values? The dial one if 6 times more expensive than the pocket one. Is it worth paying more?

 

[oldestguy]

Sounds like a "gimmick". A larger diameter cone device may be a better investment for sands.

 

[EireChch]

I have never heard of a penetrometer that assess phi and cohesion. Penetrometers are dodgy in cohesive soils and can give unrealistically high results due to skin friction on the rod shaft. We use a hand held shear vane which gives us an undrained shear strength for clays and silts. For sandy soils we use a scala penetrometer, pretty standard. Count the amount of blows per 100mm. 2 blows per 100mm = 200kpa ult, 5 blows per 100mm = 300kpa ult.