Coupling effects of cyclic confining pressure and loading frequency on deformation behavior of saturated soft clay under intermittent cyclic loading

After the train passes away, the subgrade soils undergo cyclic loading and intermittent periods. The existence of the intermittent period can also affect the mechanical properties of soil. During the cyclic loading period, the stress field of the soil element caused by the traffic loads undergoes cyclic changes in deviator stress and confining pressure, and the response frequency of the soil also changes. Therefore, the deformation characteristics of saturated soft clay under intermittent cyclic loading are studied by conducting the cyclic triaxial tests, and the effects of the cyclic confining pressure and loading frequency are also analyzed. The results show that the accumulated axial strain increment generated at each loading stage under different experimental conditions decreases with the loading stage, and the attenuation degree of strain increment is related to the cyclic confining pressure and loading frequency. The existence of the cyclic confining pressure makes the attenuation degree of the accumulated axial strain increment of each loading stage more obvious. The larger the loading frequency, the more severe the attenuation degree of strain increment. Besides, the differences in the strain increments under different experimental conditions are most significant at the first loading stage, where the strain increment decreases with the increasing cyclic confining pressure and loading frequency. However, the differences in the strain increment can be ignored at subsequent loading stages. Based on the above experimental results, a model for calculating the accumulated axial strain of soft clay under intermittent cyclic loading considering the influences of the cyclic confining pressure and loading frequency is proposed, and the predicted results are in good agreement with the measured values. The above research results contribute to a deeper understanding of the dynamic characteristics of soft clay under the intermittent cyclic loading, and can also provide technical support for the design of transportation engineering.