STUDY ON SEISMIC SUBSIDENCE CHARACTERISTICS OF STRUCTURAL SOFT CLAY UNDER BIDIRECTIONAL NEAR-FIELD EARTHQUAKES

The seismic subsidence effect of soft clay is closely related to the structural properties of the soil, but there is still relatively little research on the effect of the structural strength of the soil on seismic subsidence. Because it is difficult to obtain soils with the same composition but different structural properties in nature, soft clay with a similar composition but different structural strengths is prepared artificially to conduct an in-depth study of the seismic subsidence characteristics of structural soft clay under the coupling effect of P and S waves. Two sets of dynamic triaxial tests under dynamic confining pressure were then carried out to investigate the law of the effects of structural strength, bi-directional dynamic loading, and the phase difference between P and S waves on their seismic subsidence characteristics. The test results show that under bi-directional excitation, the larger the ratio of axial dynamic load to structural yield stress, the more pronounced the accelerating effect of the coupling of bi-directional dynamic loading on the accumulation rate of axial residual strain. The effect of phase difference on the axial residual strain depends on the structural strength of the soil, and the smaller the structural strength, the greater the effect. In bi-directional near-field earthquakes, radial dynamic loading generally accelerates the development of seismic subsidence, and the magnitude of the acceleration is related to the structural strength of the soil: the lower the structural strength, the more pronounced the acceleration. However, the shear action of axial dynamic loading still plays a dominant role in the accumulation of residual strain in structural soft clay. The results of this study can provide a useful reference for comprehensive disaster prevention in soft clay areas.