相对密实度对随机波与定次数波作用下土体变形关系的影响

Effect of Relative Density on the Relationship between Soil Deformation under Irregular Waves and Fixed-number Waves

通过砂土的一系列动三轴实验,研究不规则地震荷载作用下与定次数等幅荷载作用下土体变形间的关系,给出砂土相对密实度对二者间关系的影响规律。结果表明:真实地震荷载下土的变形发展与等幅正弦荷载明显不同,应变发展时程的形态主要受地震动的形态控制;应变比C与砂土相对密度间关系具有规律性,随相对密度增大而降低,若采用以20周作为标准作用次数、0.65倍地震波峰值为等幅荷载代替不规则的地震荷载,修正真实地震应力下的残余变形,其应变比C随砂土密实度的增大而减小。同时,冲击型荷载的应变比C`要远大于振动型荷载。

Conversion methods from seismic loads to uniform-amplitude loads are basic research topics in geotechnical earthquake engineering.Through a series of dynamic triaxial tests,the feature of soil deformation under irregular seismic wave loading and the relationships of soil deformation under irregular seismic wave loading and fixed-number wave loading are analyzed.The ratio of residual strain under a constant-amplitude sinusoid wave with 20 cycles and an amplitude of0.65 times the seismic wave peak value to residual strain under seismic loading is defined as the strain ratio C,and the relationship between the strain ratio Cand sand density is investigated.The results show that soil deformation development under irregular seismic loading obviously differs from that under sinusoidal loading,and the strain time history is mainly controlled by the performance of ground motion,rather than seismic loading amplitude and soil type.Under impact loading,the peak value（instead of other pulses）plays a significant role in control.Under a vibrating wave,besides the peak value,some other pulses with similar amplitudes and peak values have influences on the soil deformation.The strain ratio Cwill decrease with the increase of the relative density of the sand.When uniform sinusoidal loading,with 20 cycles and an amplitude of 0.65 times the seismic wave peak value,is employed instead of irregular seismic loading to modify residual deformation of soils under real seismic loading,the strain ratio C will decrease with the increase in the relative density of the sand.Meanwhile,the strain ratio Cof impact-type loads is much larger than that of vibrating loads.