扁铲侧胀试验在浅海钙质土力学特性评价中的应用

Application of flat dilatometer test to mechanical characteristics evaluation of calcareous soil in shallow water

利用扁铲侧胀仪对海底浅层钙质土进行原位测试,能够一次获得多个评价土性的试验参数。试验表明,由于波浪循环动荷载的作用使得海底表层(深1～2m)钙质砂的密实度比其紧邻的下部偏大,以珊瑚礁为主要胶结物的钙质土,内部具有大的孔隙或松散堆积体结构是造成海底浅层钙质砂表层与浅部土体的扁铲侧胀压力明显变化的主要原因。扁铲试验结果与现场标准贯入试验具有较好的相关性,基于Seed公式推导的适合于计算水下平均动应力比的简化公式能够较好地用于对不同地震烈度下海底浅层钙质土液化可能性的判别。

Several experimentation parameters which for evaluating soil indexes were obtained based on the flat dilatometer test of calcareous soil in shallow water. The reasons of the calcareous soil density at surface layer in shallow water is bigger than that of deep-sited soil are not only the wave cycle dynamic loading, but also because calcareous soil were made of coral reef cementation material; and it has big pore and relax deposit material. So the flat dilatometer pressure is obviously different between surface layer calcareous soil and that of deep-sited soil. Also it has preferable correlativity between flat dilatometer test results and on-site standard penetration test results. Liquefaction estimation of calcareous soil in shallow water under different earthquake intensity can be obtained utilizing Seed simplified eouafion which is fit for calculating under-water mean dynamic stress ratio.