MRM,
Even if you did dry the sample in the oven at a lower temp (60c) you would still have hygroscopic moisture in clay. Clay has bound water that makes up part of its structure. If you cook the bound water out of the clay at a higher temp (110c) the size of the clay particle will change, hence...
Ashayeri
We use a vacuum to presaturate (deair the system and sample) prior to back pressure saturation. Fat clay has never been a problem for us, even though the vacuum is the least effective on a stiff clay. As Focht3 pointed out, filter paper strips have to be used. Many times an...
Rickos
If pore pressure is measured the effective stress can be determined. The difference as you probably already know is that the TX-CU-PP test is an undrained test. You can of course plot the effective stress path (pq) but the values may be different from a drained test due to the fact that...
I know the measurements of the brass liners or rings that are used in the mod cal sampler. The typical liner is brass or steel and the OD is 2.5" ID 2.42 (thin wall) ID 2.375" (thick wall). The thin wall is the most used and the OD is consistent while the ID ranges from 2.4 to...
Focht3:
Are you trying to dazzle me with brilliance or baffle me with bullshit?! I think the latter. I am not even going to address what you said. Rather I will stick with some logic. The secondary consolidation has nothing to do with the Pc. The Pc is determined on the X axis. The secondary...
Focht3:
Wow! I got you going. I will try to answer your questions sequentially:
I realize that apperant cohesion can be caused by things other than negative pore pressure caused by dilation or partial saturation or cementation. I also know that I have allot to learn!
1)You should know what...
cmorgh:
Remolding samples are never the best or representative approach. If you are working with granular materials that don't really have a structure then remolding to the same moisture and density may be usefull. You have to be sure to make the diameter of your remolded sample at least 6...
Focht3 & JDMM,
Thanks for the response guys. I see where Focht3 is going with the differences due to secondary compression in one test but not the other. Same thing with the total vs effective stress path. I don't think that is an issue since what we are trying to acheive in both methods is an...
Focht3:
I think I get the idea of a uniform clay particle orientation from running torsional ring shear to determine residual strengths. The clay particles have to be aligned.
A while back I ran some stress path testing. The method was to take a triaxial sized sample (min. height = area x...
cmorgh:
I forgot to mention that there are 6" diameter shelby or pither tubes if you have to have undisturbed samples. We have those come in the door but usually just on litigation testing jobs with lawyers from both sides watching every move we make. I finally figured out how to get rid...
cmorgh:
Gravel always complicates things in the lab. What we do is run a gradation to find out how big and how much of the big stuff we have. We then batch the sample and remold. What I mean by batching is to fabricate the sample to the exact gradation of the as received material. If we run...
Way back when I used to do field density testing we used to calibrate both inside and outside of the trench then apply a correction. I can't remember what the correction was. We would also take moisture samples back to the lab to check against the meter mc. It was the moisture that was affected...
I have noticed that the constant rate of strain consolidation test will typically show a higher Pc or max past pressure than the incremental. Can the standard construction typically used for the incremental consol be used for the CRS? I have had clients mention to me that the CRS tests showed...
I have heard that the smaller the diameter the higher the strength will be. I have not researched this as it is not that important to me. I wouldn't suggest using anything under a 2.5 inch diameter for strength testing or 3 inch for consolidation testing unless a piston sampler is used. I have...
