Sampling and Testing Loess Soils

[moe333]

I am trying to evaluate the collapse potential due to wetting of soils in the southeast California desert. I am currently planning a geotech. investigation for a lined canal and am looking for advice on how to sample and test the soils.

Some of the areas are in sand dunes so I am thinking the soils will be very easily disturbed and therefore difficult to determine the collapse potential. The more clayey soils could likely be sampled with short pushes of a shelby tube, but the silty and sandy soils will be more difficult to obtain an undisturbed sample. I plan to run single and double odometer tests once I obtain the samples.

Any experience out there on sampling the sandy and silty loess, or on other means of insitu evaluation of collapse potential, possibly from CPT testing?

Thanks

 

[Focht3]

You will have to hand trim some bulk samples - California sampler will densify the samples and make the testing worthless.

Here's an easy field test procedure I used on one of the Orange County toll road projects (tie-in between SR 91 and the east toll road at Bee Canyon):

Dig a trench and stair-step one end so that you can run nuclear densities every 2 feet of depth. After you complete the densities, observe the backfill and measure the size of the depression. At Bee Canyon, we dug a 15 ft trench and were left with a 6 ft depression - a 40% loss of volume without the influence of water!



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"