Dynamic behavior of sawdust-mixed soil in shaking table test

Abstract

In the shaking table tests of underground structures, the scale ratios of the soil and structure are inconsistent. To this end, a scaled model soil was developed in this study. Through a series of tests, the dynamic response of the model soil was investigated. A clay mixed with sawdust was designed for shaking table tests based on the predominant period similarity relationship between the structure and the foundation soil. The sawdust-mixed clay was subjected to a series of shaking table tests at Beijing University of Technology using a rigid prefabricated continuous model box (dimensions: 7.7 m × 3.2 m × 1.2 m). Through the tests, the performance of the model box and the nonlinear seismic behavior of the model soil were studied. The results are as follows: (i) The boundary effect of the model box was negligible during the test. (ii) The predominant frequencies of the model soil shifted toward lower values with increasing shaking intensity. This indicated that the model soil became increasingly softer and that the nonlinear effect of the soil was more evident. (iii) With the increase in the shaking intensity, the peak acceleration of the model soil at the same measured points increased, whereas their amplification factors decreased. In addition, the amplification factors first decreased and then increased from the bottom to the top of the soil. This might have been due to the increase in the shear strain and decrease in the shear modulus of the soil with increasing shaking intensity. (iv) The shear modulus of the soil was closely related to the confining pressure. At the same shaking intensity, the shear stress increased, and the shear strain decreased from top to bottom of the model soil.