Sampler Trials in Overconsolidated Sensitive Clay

During the excavation of pump wells for a sewage treatment plant, it was possible to obtain large, undisturbed, block samples of extremely sensitive yet overconsolidated clay from depths ranging from the surface to 70 ft. With these block samples as a reference, sampling was conducted with four types of piston samples, and the test results were compared with those obtained from the block samples. The in situ strength of the clay also was measured with the field vane test. Samplers used in the trials were the Swedish Foil, the Norwegian 54 mm, the Swedish 50 mm, and the 5-in.-diameter Osterberg hydraulic sampler.

The results showed that none of the samplers nor the field vane test were successful in obtaining results that could be compared consistently with results obtained from the block samples. The main conclusion of this study is that present methods of sampling of such soils by boring from the surface do not produce satisfactory undisturbed samples in this material.