Unconfined Compression Strength Correlation with Shear Wave Velocity
Unconfined Compression Strength Correlation with Shear Wave Velocity
(OP)
Do any of you have references for or know of any correlations between unconfined compression strength and shear wave velocity? Specifically for hard rock?





RE: Unconfined Compression Strength Correlation with Shear Wave Velocity
In the interest of full disclosure, however, I should tell you that my knowledge of rock mechanics literature ends about 1983, when I finished my MS thesis "Undrained Behavior of Rock Joints Under Dynamic Loading."
RE: Unconfined Compression Strength Correlation with Shear Wave Velocity
http://su
If you're after references or more details get hold of any of Marcus Matthews papers or try Gerhard Heymann & Sebastiano Foti.
Am currently trying to finish my MSc project looking at shallow surface waves so have tons of papers if you need details!
RE: Unconfined Compression Strength Correlation with Shear Wave Velocity
Maybe RQD would be a better predictor than unconfined, if RQD is available.
RE: Unconfined Compression Strength Correlation with Shear Wave Velocity
Go = p*Vs2
Where p = Bulk density, Vs = Shear wave velocity
As dgillette says this could be misleading depending on how fractured/jointed the rock is as failure is often due to weakest plane rather than in-situ strength.
RE: Unconfined Compression Strength Correlation with Shear Wave Velocity
Go = p*Vs2"
That's not what the original post is looking for. He is looking for a correlation between unconfined compressive strength and SWV.
RE: Unconfined Compression Strength Correlation with Shear Wave Velocity
The rock was noted at the bottom of several hollow stem auger boring that were conducted. The shear wave velocity was 5600, and 5900 ft/s. This seems somewhat low for most of the granitics I have seen before, but it is high enough to make me think it will still act in as a fairly hard rock would. I am specifically thinking about end bearing for piles, and bearing capcity of spread footings.
I have asked our geologist to give me an estimation of what he thinks RQD would be from his experience, but we do not have actual core to get it from, or I would have just goten the unconfined from that.
I have tried to use the path that Rockmynci was suggesting to correlate with the elastic modulus and back into the strenght that way, however the units are not right.
If you use Go = P*Vs^2 and substitue into the E = 2*G*[((2+nu)*(1+nu))/nu] for transformation between shear modulus and elatic modulus you will get units of lb/(ft*sec^2). For that matter you would get those some units for Go.
Did I miss my units along the way somewhere?
RE: Unconfined Compression Strength Correlation with Shear Wave Velocity
[150 slug ft/s^2/ft^3] / 32.2 ft/s^2 = 4.66 slug/ft^3
Yuck. Why the didn't we ever go to the metric system?
My cheat sheet shows 5000 ft/s as typical for shale, siltstone, soft limestone, and schist, and maybe even some denser tills. 5000 ft/s -> G ~800,000 psi.
RE: Unconfined Compression Strength Correlation with Shear Wave Velocity
Using the general form of the transformation between shear moduli and elastic moduli E = 2(1+v)*G
(I was mixing up my moduli earlier too)
would give about 3000 psi unconfined compression for rock at 165 pcf and 5,900 ft/s, and assuming poissons of 0.2 and limiting strain to 0.001.
That seams more reasonable.
RE: Unconfined Compression Strength Correlation with Shear Wave Velocity
Chapter 2.8 gives values of shear wave velocities for different minerals.
RE: Unconfined Compression Strength Correlation with Shear Wave Velocity
Are you analyzing the ReMi data yourself or is someone else? What is your equipment setup (phone freq, takeout dist, recording length and sample rate)? What depths are you dealing with? The book BigHarvey mentions is good place to get lots of data. I have profiled deep tunnel alignments and correlated to RQD with "good" results (as geophysical data goes) and may be able to help. Gut feeling says the velocities are a bit too low.
Shoot me a g mail message if you prefer.
RE: Unconfined Compression Strength Correlation with Shear Wave Velocity
How well can you work up RQD from the shear velocity? That would help me some if it is possible? I was kind of assuming a moderate amount of jointing and weathering from the low velocity number, but the rock itself from the contact looked decent. So it was hard for me to judge.