What type of triaxial tests,cd?cu?uu?
What type of triaxial tests,cd?cu?uu?
(OP)
hello everyone, if an earth dam is to be constructed. The soil on the site is clay. The initial water level is at the ground surface. During the construction, the water level has to be lowered in a short time, so that construction can proceed. This condition is commonly known as "sudden drawdown". What type of triaxial tests would you recommend to carry out, and why?





RE: What type of triaxial tests,cd?cu?uu?
The term "sudden drawdown" is usually reserved for rapid lowering of a reservoir after the dam is in operation, rather than dewatering for an exc. Clay generally does not allow for sudden dewatering.
It would make it easier to give good advice if you would explain a little bit more about the site and what you intend to analyze. In geotechnical engineering, even the easy questions are complicated by issues that are specific to the site and what is being sought.
RE: What type of triaxial tests,cd?cu?uu?
RE: What type of triaxial tests,cd?cu?uu?
If you want the immediate strength that governs the strength of the foundation for stability during construction, you could use UU triax tests, but I very well might put my money into cone penetrometer tests, field vane shear tests, and oedometer consolidation tests instead (depending on details of the situation, which you have not provided).
RE: What type of triaxial tests,cd?cu?uu?
moreover,if in first priority just focus on traxial test. i think result can found from both types of triaxial test, but except the time & money concerning, would you mind telling me the reason & difference on your decision, also, what 's the different on the result of triaxial test, cone penetrometer tests, field vane shear tests?
RE: What type of triaxial tests,cd?cu?uu?
VST: Still requires empirical adjustment, but regarded by many as more reliable than CPT. Gives sensitivity of clay directly. Not as fast or cheap as CPT, but still much cheaper than undisturbed samples and triaxial tests. The strength results can be used to verify or calibrate the CPT strength results. In each drill hole, VST can be alternated with undisturbed samples for oedometer tests and index properties, or for a few triaxial tests if still needed.
Oedometer tests: Usually need them because preconsolidation pressure governs almost everything with clay behavior, and you generally need to know whether the strengths you measure by CPT and VST are from over-consolidated clays. Besides, you need oedometers to estimate settlement of the embankment.
This is as much time as I will put into this discussion. Like most of the people who use eng-tips, I am happy to help with specific questions, but this is a very general discussion of a complicated topic. Before any further discussion, you should read C.C. Ladd's Terzaghi Lecture on clay strengths, which appeared in the ASCE Journal of Geotechnical Engineering in August of 1991.
RE: What type of triaxial tests,cd?cu?uu?
RE: What type of triaxial tests,cd?cu?uu?
RE: What type of triaxial tests,cd?cu?uu?
However, there are some additional factors to consider including moisture conditions in the clay during and after rapid drawdown which will affect undrained shear strength and whether to rely on negative pore pressures in overconsolidated clays.
I think a reasonable approach may be to adopt a effective stress/total stress envelope for low confining stress zones of the dam/foundation.
Everybody has an opinion on rapid drawdown and how to treat it.