ASTM D4015 is tricky, what's it mean 1

[techmaximus]

Anybody ever performed the ASTM D4015 Standard Test Methods for Modulus and Damping of Soils by the Resonant-Column Method which covers the determination of shear
modulus, shear damping, rod modulus (commonly referred to
as Young’s modulus), and rod damping for solid cylindrical
specimens of soil in the undisturbed and remolded conditions by vibration using the resonant column? And if so WHY? Is there a referenance other than the ASTM standard that explains this proceedure in terms that can actually be understood?

SCET - Techmaximus

 

[bb5dad]

Whoa. Haven't heard this one in quite a while. While employed as lab manager for a So Calif geotech consulting firm in the the late 70's - early 80's, I ran this test on maybe a dozen or so projects. It's used to determine the stress-strain properties of soils at relatively low strain levels, where the soil is still mostly elastic. The data obtained from the test is used in dynamic (earthquake) computer response analyses, such as soil-structure FEM programs, and dynamic soil analyses, such as SHAKE or FLUSH, programs of the type that were developed by Profs. Harry Seed and John Lysmer (both now deceased) at UC Berkeley. Stress-strain properties at higher strain levels are obtained from dynamic triaxial loadings. The computer analyses I mentioned are non-linear, meaning they iterate on soil properties until they get a convergent solution.

The equipment I used at the time was developed by Bobby Hardin and was referred to by us as a Hardin Oscillator. I don't remember the specifics of the ASTM spec, and I didn't look at the spec before posting this response, but we used instructions provided by Hardin. Baseically you confine the sample in a triaxial-type chamber under pressure to simulate field conditions, and apply a low-frequency sinusoidal torsional driving force using a signal generator and a small electric motor. Our setup used a 1.4" sample size. We used a storage oscilloscope to capture the hysteresis loops of the sample, from transducers on the sample, as it oscillated at resonance.

I remember that we had some difficulty understanding the test at first, but it wasn't that difficult and once understood was a pretty easy test to run. Because the test is run at low strain levels and is non-destructive, we would reuse the same sample at different confining pressures, without removing it from the chamber.

Good luck, post again if you actually get into running this test.