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Many recent publications on the influence of sampling techniques indicate that, generally speaking, the quality of the samples increases with the diameter of the sampling equipment. However, all studies also conclude that even the large diameter samplers available on the market substantially damage the structure of the clays of eastern Canada, as compared to the sample quality obtained by block sampling. In addition to the difficulties associated with the excavation of the trenches necessary for block sampling, the depth of block sampling is limited, at least in soft clays.The sampling technique described in the present paper allows the retrieval of deep blocks, working from the ground surface and using a cutting method quite similar to that used for conventional block sampling. The large diameter borehole is filled with water or bentonite slurry to reduce the possibility of bottom heave. By comparing the results of unconfined compression tests it is shown that the samples obtained by this method are of a quality equal or superior to that of blocks sampled conventionally at the bottom of open cuts.
Lefèbvre et al. (Thu,) studied this question.