pentrometer/shear vane

Hi,

I am an emergency worker and am currently preparing for a trench rescue course. In the course material mention is made of a pocket pentrometer and a shear vane. It is mentioned in the course material that both are used to determine "unconfined compressive strength of the soil sample". I have no idea what either of these pieces of equipment looks like or how they are operated. I would really apreciate it if someone can help me.

Thanks in advance

Regards

 

[Ginger]

These pieces of equipment measure the undrained shear strength of the soil.

The hand shear vane is a steel rod with 4 "fins" on the bottom which form a cross. The top of the rod is connected to a spring loaded disc which has a calibrated scale on it. You insert the rod into the ground and then rotate the disc slowly by hand to put torsion into the rod. This torsion is resisted by the fins buried in the soil. Eventually, the torque generated will be too great and the soil around the fins will fail in shear and the fins will spin in the ground. The torque at which the failure occurs can be read on the disc and directly correlated to the shear strength of the soil.

The pocket penetrometer is a small circular rod housed in a larger tube with a calibrated spring at the rear end. The rod is inserted into the soil to a predetermined mark on its length. The force required to do this will cause the spring to be squashed a certain amount which gives a direct shear strength reading. Andy Machon

 

Thanks

 

[dirtman]

The vane shear tester is far superior to the pocket penetrometer. Both are only applicable for saturated, at least moderately plastic clays. It is inappropriate to run the tests on unsaturated clays or soils with plasticity indices less than about 10. The best vane shear tester in my opinion is made by Geonor. Look for it on a web search engine such as google.