Study on strength criterion for frozen soil

Abstract

Abstract It is established that the strength of frozen soil exhibits apparent nonlinearity in the p–q plane. As the mean stress p increases, in certain experimental conditions, the strength of frozen soil increases rapidly and then reduces gradually; however, in certain other conditions, the strength increases gradually and then reduces rapidly. The former phenomenon is said to be of the “front peak” type, and its critical confining pressure is relatively smaller. The latter phenomenon is said to be of the “back peak” type, and its critical confining pressure is relatively higher. Only a few cases are considered as “symmetric”; these exhibit forms analogous to a parabola opening downward. Based on these observations, it is determined that the temperature, soil type, salt content, strain rate, thawing cycle times, and particle size of the sample determine the type of the strength curve. With the present level of research, most of the strength criteria can consider only one of the three types. Thus, a new strength criterion that can be simultaneously applied to the three types of strength-changes, and the corresponding strength criterion in the deviatoric plane are proposed. Moreover, two concepts—“calculated cohesive force (c0)” and “calculated internal frictional angle (φ)” of frozen soil—are proposed as fundamental mechanical parameters for various strength criteria.