Comparative Observations on the Use of the Pitcher Sampler in Stiff Clay

Recent experience in the use of the Pitcher sampler is described, and modifications to it which have improved performance are noted. Block samples of till have been obtained from a depth of about 85 ft below the ground surface. The following properties were determined in order to compare the borehole samples with the block samples: (a) swelling pressure, (b) compressibility, (c) permeability, (d) undrained strength, (e) compressional wave velocity, and (f) classification indexes. While differences between the results of Pitcher samples and Shelby tube samples are detectable, they are small when compared with the differences between the results from block samples and borehole samples. Contrary to expectations, the block samples have lower strengths and higher permeabilities. It is concluded that the block samples are more disturbed than those obtained from boreholes. With regard to borehole methods, the Pitcher sampler is judged preferable because samples can be recovered from stiff clays and soft rocks with a higher recovery ratio and with greater ease.