Evaluation of Sample Quality of Sensitive Clay Using Intrinsic Compression Concept

A simple index, the degree of sample disturbance, is proposed in this study to quantitatively evaluate the quality of sensitive clay samples based on the concept of void index proposed by Burland in 1990. The degree of sample disturbance is defined as the ratio of the difference between the in situ void index and the void index of the undisturbed sample tested in the laboratory to the difference between the in situ void index and the void index of the completely remolded clay. All these indices are determined at the same effective overburden stress. Theoretically, the degree of sample disturbance varies from 0% (perfect undisturbed sample) to 100% (completely remolded sample). The proposed index is used in this study to evaluate the sensitive Ariake clay in Japan. Oedometer tests on undisturbed samples of natural Ariake clay obtained from the field using the current sampling practice in Japan show the degree of sample disturbance ranging from approximately 5 to 38%. The clay sample with an in situ void index closer to the intrinsic compression line has a lower degree of sample disturbance. In addition, a series of consolidation and unconfined compression tests were conducted on artificially disturbed samples in the laboratory to demonstrate the change of consolidation yield stress, unconfined compressive strength, and compression index with the degree of sample disturbance. A simple method is proposed in this paper to correct the mechanical parameters measured in a laboratory setting considering the degree of sample disturbance.