Undisturbed Sampling of Saturated Sands by Freezing

From considerations of the basic mechanisms of soil behavior during freezing, it is suggested that undisturbed samples can only be obtained by undirectional freezing with no impedance of drainage while the confining pressure is maintained. Experimental data illustrate that this method can lead to laboratory samples which maintain their in situ characteristics. Care is required to ensure the effectiveness of the method and it is noted that variables such as the coolant temperature, the percentage of fines in the sand and the depth of sampling can influence the efficiency and effectiveness of the method. It is shown that the beneficial effects of freezing samples by surrounding the sampling tube with dry ice prior to shipping can only be achieved if the samples are drained prior to freezing. If a sample contains a large percentage of fines, insufficient drainage may cause all-around freezing to have deleterious effects on the quality of the sample.