地震荷载作用下南海非饱和钙质砂动力特性研究

Dynamic characteristics of unsaturated calcareous sand in South China Sea under seismic load

以往对钙质砂动力特性的研究多关注饱和状态的钙质砂,且试验过程中多施加正弦波以代替地震荷载。为克服这一缺陷,提出一种地震荷载加速度时程转化为应力时程的动三轴地震荷载输入方法,选取南海地区钙质砂进行动三轴试验,研究非饱和状态下钙质砂在单个地震荷载持续时间内和多个地震荷载持续时间内的动力特性。试验表明:在地震荷载作用下,钙质砂应变和孔压发展呈现阶梯状,破坏应变既有正值也有负值,即破坏类型既有拉伸破坏也有压缩破坏,这有别于正弦荷载下的动孔压和动应变发展规律;随着基质吸力增大,试样破坏时最大动孔压呈现递减趋势,钙质砂试样破坏时的最大孔压均未达到有效围压。

Previous studies on the dynamic characteristics of calcareous sand mostly focused on the saturated calcareous sand,and sine waves were often applied to replace seismic loads in the test process.In order to overcome this defect,a dynamic triaxial seismic load input method is proposed to convert the acceleration time history of seismic load into stress time history.Dynamic triaxial test on calcareous sand in the South China Sea is conducted to study the dynamic characteristics of unsaturated calcareous sand in single and multiple seismic load durations.The test results show that the strain and pore water pressure of calcareous sand develop in a stepwise manner under the seismic load,and the failure strain has both positive and negative values,that is,the failure type has both tensile failure and compression failure,which is different from the development laws of dynamic pore water pressure and dynamic strain under sinusoidal load;with the increase of matrix suction,the maximum dynamic pore pressure shows an decreasing trend,but the maximum pore pressure of calcareous sand samples does not reach the effective confining pressure.